PLEASE NOTE THAT THIS FAQ IS OUT OF DATE. Work is being done to move this to a wiki format with updated information, but please check out the TDIClub forums (http://forums.tdiclub.com) in the mean time for more updated information.
Disclaimer: While considerable effort has been
made to make the information provided in this section
as complete and accurate as possible, it does not and
cannot cover all possible situations. The authors cannot
accept any responsibility for any damages which may occur
from the use or mis-use of these procedures, nor can the
authors accept any responsibility for any damages which
may result from personal injury or property damage which
allegedly may be caused by the use or mis-use of these
procedures. No responsibility is accepted for missing
or incorrect information. Those who use these procedures
shall accept all responsibility for performing the work
which may be described below. If you have any comments
or suggestions for additions or revisions, please contact
the site administrator.
References within this document to "left" or
"right" always refer to the orientation viewed
from the driver's normal seating position. Throughout
this document, you will see references to VAG-COM. Many
diagnostic and calibration procedures cannot be performed
without a VW specific diagnostic scan tool. VAG-COM is
a reasonably priced software and cable that allow any
Windows based computer to be used to communicate with
the vehicle's on-board diagnostic system. Generic OBD-II
code scanners (such as those which may be found at independent
garages that do not specialize in VW/Audi) will normally
NOT be sufficient - you need a VW specific scan tool.
For more information about VAG-COM and to purchase a copy
for yourself, see www.ross-tech.com - highly recommended.
Know which model you have. If you have a '96 or '97 Passat
TDI in North America, you have a B4 chassis with what
is known in this document as an A3-style engine, and you
have a Garrett GT15 turbocharger. If you have a '97 through
early '99 Jetta TDI in North America, you have an A3-style
engine and you may have the Garrett GT15 turbocharger
but more likely you have a KKK K03-006 turbocharger. If
you have a New Beetle TDI, or a '99.5 or later Jetta or
Golf TDI in North America, you have an A4-chassis vehicle,
and you have a Garrett VNT-15 turbocharger.
The engine code number can be found on the build sheet
which is typically near the spare tire on the floor of
the trunk. In North America, engine code 1Z means 90hp
A3-style engine with Garrett GT15 turbocharger and Pierburg
MAF (mass air flow sensor). Engine code AHU means 90hp
A3-style engine with KKK K03-006 turbocharger and Pierburg
MAF. ALH means 90hp A4-style engine with Garrett VNT-15
turbocharger and Bosch MAF. European models don't necessarily
correspond in specifications, engine codes, and model
years (you're on your own, as far as figuring out what
type of turbo and MAF sensor you have).
a. Engine Oil and Filter Maintenance
b. Fuel Filter / Water Separator Maintenance
c. Air Filter and "Snow Screen"
d. Timing Belt Inspection and Replacement
e. "Supplementary injector"
on 1996 Passat TDI models - North American specification
f. Intercooler Cleaning
g. Intake Manifold and EGR Cleaning
h. Solving the "Slow-down Shudder" and Other Shudder Issues - Recalibrating the Fuel Quantity at Idle
i . Engine Power Supply Relay a.k.a. "Relay 109" Replacement
j .Avoiding the Need for Intake Manifold
Cleaning - Recalibrating the EGR System
k. Setting the Injection Timing - Injector
Pump Mechanical Adjustment
l. MAF sensor - checking and replacement
Back to FAQ Index
Engine Oil and Filter Maintenance
-Your owners manual contains a recommended change interval
for normal driving conditions, which is either 12,000
km / 7500 miles (older models), or 16,000 km / 10,000
miles (newer models). Some forum members have used oil
analysis to determine a suitable change interval. There
have been cases where, using synthetic oil rated CH-4,
the 10,000 mile / 16,000 km interval was appropriate.
There have been other cases where shorter intervals were
warranted, generally using oils which were either not
synthetic or did not have the CG-4 or CH-4 rating.
Based on the available information from oil analysis,
an oil change interval under normal conditions of 16,000
km / 10,000 miles (or 1 year whichever comes first)
is recommended when full-synthetic 5w30 or 5w40 oil
meeting CG-4, CH-4, or CI-4 standards is used, as per
the owner's manual. Note that owners manuals may not
refer to the latest specifications for certain types
of oils. Oil specification CI-4 supercedes CH-4, which
already superceded CG-4 some time ago. Oils conforming
to CH-4 or CI-4 (latest standards) may (and should!)
be freely substituted for the owner's manual requirements
for older specifications, without question.
If semi-synthetic, synthetic blend, or Group III oil
is used which meets CG-4, CH-4, or CI-4 standards, an
oil change interval under normal conditions of 12,000
km / 7,500 miles (or 6 months, whichever comes first)
For conventional non-synthetic oil which meets CG-4,
CH-4, or CI-4 standards, or for any oil meeting older
standards such as CF, an oil change interval under normal
conditions of 8,000 km / 5,000 miles (or 6 months, whichever
comes first) is recommended. Castrol Syntec recommended
by many dealers falls into this category, as it is a
Group III oil meeting the CF standard. Mobil 1 also
falls into this category as it meets only the CF standard,
ACEA B3 or B4 rated oils are also acceptable, at least
for 2001 model year vehicles. In North America, the
ACEA B3 and B4 rating is found on some *W-40 (and *W-50)
oils that are not marketed as diesel engine oils (the
latter would normally have the API CH-4 rating). They
may be marketed as "oils for European engines"
or some such.
API CF is not the same as API CF-4. Many more oils
carry the API CF rating, compared to the number of oils
that carry the API CF-4, CG-4, or CH-4 rating, but these
are not suitable for TDI use unless they also carry
another appropriate rating, such as ACEA B3 or B4.
If conventional oil of 15w40 viscosity is used, expected
weather conditions also need to be taken into account,
as the cold pumping ability of this oil is much less
than that of the recommended 5w40 viscosity.
In the case of adverse driving conditions, such as
trailer towing, mountain driving, driving under hot
or dusty conditions, or driving consisting of mostly
short trips, the oil change interval should be reduced.
Some forum members have installed oil bypass filtration
units which continuously remove particles smaller than
can be removed by conventional filters. Oil analysis
indicates that these can safely extend oil change intervals
far beyond what is conventional.
With the A3-type engine in a B4 Passat, removal of
the lower engine pan is not necessary to change the
oil. The drain plug is located at the rear of the oil
pan, facing down at an angle, and is easy to reach.
The oil filter is another matter, it's notoriously difficult
on A3/B4 cars but it's possible to do from above. On
a 1996 B4 Passat, there is a radiator hose blocking
access, but this can be pulled out of the way without
disconnecting it. A conventional strap-type oil filter
wrench can be worked into position on the filter to
remove it. Some oil spillage onto the lower engine pan
is unavoidable. Before installing the new filter, pre-fill
it with fresh oil, to minimize the amount of time that
the engine runs without oil pressure. Then, the hard
part is getting the new filter started on the mounting
threads, because you can't see what you're doing, there's
hardly room to feel your way, and you don't want to
spill that brand new expensive synthetic oil now contained
in the filter! With enough persistence, it can be done.
With the A4 models, the filter is a cartridge type,
and is a snap to change, but the lower engine pan has
to come off for access to the drain plug. You win some,
you lose some!
Leaving the lower engine pan off, to facilitate oil
changes, isn't recommended. The lower pan performs several
functions. It isolates a certain amount of noise, it
keeps more heat within the engine compartment, it protects
many components from debris thrown up from the road.
Back to Top
Fuel Filter / Water Separator
-Diesel fuel is filtered through a combination
filter and water separator. The water collection chamber
is in the lower portion of the unit, and the filter
medium is in the upper portion. There is a drain in
the bottom of the water separator to permit removal
of any accumulated moisture without the need to remove
the unit. This drain should be opened to drain any collected
water at periodic intervals. The entire unit of filter
and separator should be replaced periodically. The capacity
of the filter/separator is relatively large in comparison
to typical gasoline filters. It may be desired to pre-fill
the new unit with Diesel fuel before installation to
minimize starting hesitation.
The change interval for the fuel filter is either
48,000 km / 30,000 miles, or 32,000 km / 20,000 miles,
depending on model. Consult your owners manual for
your specific vehicle.
The filter is a cylinder-shaped housing with hoses
going into the top, easily visible at the extreme
right of the engine compartment. It's possible to
change the filter yourself. Make sure you have a supply
of suitable clamps before you start the job, and also
find some way to pre-fill the filter housing completely
with diesel fuel before hooking everything up again,
otherwise you'll have an awful time getting the engine
to keep running until all the air is worked out of
Back to Top
7.b.1 Using pliers, pinch and slide hose clips
away from filter (about 1 1/2in from hose ends) of
fuel feed lines. Fuel feed is traceable back to a
black line from the tank.
7.b.2 Use needlenose pliers and pull out (sideways,
towards engine) return line clip for tee-piece. The
tee-piece pulls straight up out of filter. The return
line line is traceable back to a blue line from the
tank. Wrap the tee-piece with a clean cloth or paper
towell to protect from dirt.
7.b.3 Push (do not pull!) feed lines off the filter
nipples (flat screwdriver blade helps). Wrap the
ends with paper towells to protect from dirt. Use
a Phillips screwdriver and release fuel filter clamp
(vertical screw beside filter), holding filter from
slipping down. Observe the positioning of the filter
7.b.4 Gently lift filter straight up out of the
car. Do not tip, as fuel may spill.
7.b.5 To drain the filter, on the bottom of the
filter should be a knurled knob. Hold over a glass
jar and unscrew (counter clockwise viewed from bottom)
slowly. There is a nipple here where you can attach
a short drain hose to avoid spilling. Try to contain
drained fuel to a glass jar (old widemouth jam jar).
This way you can see if there was water in filter.
Drain about two ounces of fuel, and look for water
droplets (may appear as beads, as water and diesel
do not mix).
Note that if you are draining and not replacing
the filter, it is not necessary to disconnect the
hoses; the filter can be unclamped and lifted up enough
to access the knurled knob. THIS KNOB IS VERY FRAGILE.
Don't break it off if you are going to be re-using
Some analysis of the quantity of water in the filter
is in order. It is determined by several factors,
e.g. condensation in the tank, use of fuel treatments,
and especially by your fuel supplier. If you buy fuel
from the same place all the time, it may be usefull
to check for water after say the first 5000kms as
a safeguard to see what your supplier is giving you.
If you see lots of water you may want to change to
a different supplier. Stay well away from old barrels
found lying in a field.
7.b.6 Set the old one aside and get the new one out
now and install. Watch the orientation of the nipples.
Tighten clamp you loosened in step 3 above.
7.b.7 Before you plug back on the return line tee-piece,
it is wise to prime the filter with some CLEAN diesel
fuel, and/or some straight fuel system cleaner. Failure
to so do may result in a long cranking time before
the engine starts, especially at lower temperatures.
7.b.8 Replace hoses, clamps and clip, then test engine.
7.b.9 Once engine is running, look at the "sight
tube", i.e. clear line from filter to engine
(if so equipped) - you may see air bubbles. They should
almost dissappear, but there will still be a few after
running for a while.
Note: If you have a gross amount of air bubbles,
there may be an air leak in the fuel supply side
(or the tee-piece), and it may impact engine performance.
Check hose fittings, connectors, especially the
return line plastic Tee-fitting (has an O-ring)
where it plugs on to the filter with the retaining
- Air Filter and "Snow Screen"
Maintenance - The air filter should be replaced at
30,000 mile / 48,000 km intervals or not more than 2 year
intervals. When checking or replacing the air filter,
also inspect the screen on the intake of the airbox and
clean if necessary (see below).
In some areas, due to high levels of airborne contaminants,
the "snow screen" will become clogged so quickly
(resulting in power loss) that it becomes a considerable
hassle. Many owners have removed these screens permanently
with no ill effect other than slightly more frequent
need to clean the main air filter element. The total
frequency of maintenance may be considerably lower without
the screen than with it in place ...
On A3/B4 models, the air filter housing is at the right
front corner of the car. To access it, first remove
the plastic cover between the top of the airbox and
the headlight (it just pops out). Unplug the electrical
connector at the airflow meter (between top of airbox
and the large flexible hose). Pull the clear plastic
fuel lines out of the clamp that holds them. Release
the four clamps for the airbox cover and pull the airbox
cover away to expose the filter element, which can then
be removed for inspection. Unbolt and remove the screen
which is bolted into the lower section of the air filter
housing, and either clean it or don't bother re-installing
it. This screen is very prone to clogging and some owners
have found that it is better to leave the screen out
and accept the (possibly) slightly greater frequency
of servicing the main air filter. Re-assembly is the
reverse, but don't forget to plug the airflow meter
in again, and make sure the air filter element is properly
seated in the housing at all edges and corners!
On A4 models, the air filter housing is on the left
side of the engine compartment. Release the clamps,
pull the cover off, and the filter element is right
there. Cleaning the screen requires removal of the lower
section of the airbox from the vehicle and then removal
of the duct which leads to the air filter housing intake.
Back to Top
Timing Belt Inspection and Replacement
- - The TDI engine uses a toothed belt to drive the
camshaft. The choice of a belt rather than a chain was
made for noise considerations. A Diesel engine is normally
louder at idle than a gasoline engine. A direct injection
Diesel is louder yet due to the lack of a pre-chamber
that tends to suppress some noise. Minimizing noise
sources was a high priority and a belt drive for the
camshaft is much quieter than a chain drive. All rubber
belts will fail eventually, as will chains. Chains,
prior to their failing, become more noisy, looser, and
in general give warning to their deterioration. Belts
remain nearly silent and tight right up to their sudden
failure. When the camshaft drive belt breaks, the camshaft
stops turning and the valves stop moving. The valves
that are open stay open. The pistons continue moving
up and down as the engine coasts to a stop. It is almost
a certainty that a high compression engine, like a Diesel,
will have the pistons travel in a stroke that overlaps
the stroke of the valves as they move open and close.
The camshaft normally controls the opening and closing
of the valves to occur only when the piston is clear.
If the valves are open and do not move closed when the
piston reaches the top of its stroke, the piston will
strike the valve and damage the valve and the piston.
The repair cost of this damage is often several thousand
dollars. Although timing belt replacement is not an
inexpensive operation, replacing the belt long before
its likely failure is inexpensive in comparison to the
cost of a failure. The replacement interval varies depending
upon model but is generally 96,000 km for manual transmission
models for the 2001 and prior model years, and 64,000
km for automatic transmission modeis for the 2001 and
prior model years, and 128,000 km for 2002 model year
regardless of transmission. The 2002 model has an updated
belt and tensioner design which may be retrofitted to
A4-chassis models of prior years to take advantage of
the extended change interval provided that both the
belt and tensioner are replaced. The extended-life belt
and tensioner cannot be fitted to the older A3 or B4
engines because the belt is a different length and will
The timing belt should be inspected at every oil
change interval for evidence of any abnormal wear
conditions. This is easily done by unclipping and
removing the upper timing belt cover and performing
a visual inspection. If any of the following conditions
are noted, the belt and tensioner must be replaced
immediately without driving the vehicle any further:
- More than 1 or 2 mm gap between either edge of the
belt and the base of the flange on the front and rear
of the tensioner roller - indicating that the belt
is mis-tracking and is wearing at the edges.
- Excessive wear on any of the edges of the belt,
- Evidence of cracks on the outer surface of the belt,
indicating that the rubber material is deteriorating.
- Evidence of oil, fuel, or other fluids on the belt.
These cause deterioration of the belt materials.
- Excessive wear on the teeth of the belt.
- If the belt has been on the vehicle for in excess
of the time or mileage specified in the owner's manual,
the belt and tensioner must be replaced with new components
regardless of the result of any visual inspection.
For A3 and B4 vehicles, instructions for performing
a timing belt change can be found here: http://www.tdiclub.com/articles/A3-TimingBelt
For A4-chassis vehicles, instructions for performing
a timing belt change can be found here: http://www.tdiclub.com/articles/pdf/a4timingbelt.pdf
Back to Top
on 1996 Passat TDI models - North American specification
The 1996 Passat TDI models in North America
were the subject of a technical service bulletin (TSB)
regarding the engine control module (ECM). The TSB instructed
the VW dealer network to replace the ECM and if necessary,
the injectors, with a newer version of each. The new
version of the ECM and injectors were used as original
equipment from mid 1996 onward. Some, not all, TDI engines
from before this time were experiencing this failure.
This TSB was not a recall and the replacement of the
affected components was covered under warranty terms
in most instances. The most common complaint is that,
after a period of highway driving (15 - 20 minutes),
then stopping, smoke would be emitted upon acceleration
away from the stop.
Investigation by members of this forum have traced
the problem to the "supplementary injector"
which some models were equipped with. Under certain
operating conditions, an injector located in the exhaust
system sprays extra fuel into the exhaust to keep
the catalyst warmed up. Although the official VW documentation
insists that this system is only present and functional
on models with automatic transmission (which were
never actually produced), experience has shown that
the system operates on the manual transmission models
as well. This system proved to be extremely unreliable,
and later models are not equipped with it. VW had
great difficulty getting the early models to pass
emission requirements, and hence the expensive replacement
components listed above.
Fortunately for the backyard mechanic, the "supplementary
exhaust injector" can be bypassed easily at negligible
cost. To determine if your car has this system, locate
the fuel filter on the right side of the engine compartment,
and locate the two clear plastic hoses nearby. The
smaller of the clear plastic hoses ends in a black
"T", and one of those branches goes back
to the top of the fuel filter and the other branch
goes forward and down, to the exhaust injector solenoid
mounted on the back of the airbox. The line coming
out of this solenoid can be followed through a clip
on the timing belt cover and then into a fitting on
the exhaust downpipe.
To disable the "supplementary exhaust injector"
system, pull the hose which faces forward off the
"T" at the end of the smaller of the clear
plastic hoses. Plug the hose by jamming a wood screw
or some other suitable object into the hose, then
reconnect it to the "T" (to prevent a fuel
leak). No more "supplementary exhaust injector".
This modification will not cause a "check engine"
code to be set and there are no known adverse side
Back to Top
- Intercooler Cleaning - With thanks
to many members of this forum who first discovered this
problem and then contributed many ideas on what to do
about it, here's a recommended procedure.
You will need a drain pan, a pail, some liquid dish
detergent, and a fuel container with 2 litres of kerosene
or other suitable solvent - don't use gasoline, or anything
which will attack rubber. You will also need some vise-grips
to hold the clamps open, and some channel-lock-type
pliers for opening the clamps in the first place. Alternatively,
buy some gear-type clamps that you can deal with a lot
easier than the standard spring clamps, which are a
Locate the two black plastic pipes which go from the
top of the engine down to the intercooler (which is
at the left front on an A3, or the right front on an
A4). Also locate the hose connection at the bottom of
the intercooler and make sure you can get it open (just
enough to drain fluid, you don't need to disconnect
it completely) before starting.
At some suitable location, disconnect both pipes to
the intercooler. Identify the pipe which goes straight
down to the bottom of the intercooler. (On some models,
the other pipe has some low spots in it which will trap
liquids, you don't want to pour anything down that pipe.)
Pour the kerosene into the intercooler and let it sit
for a while. If possible, agitate the liquid once in
a while by blowing into the pipe that goes to the bottom
of the intercooler by some means. After 15 minutes or
so, put the drain pan under the intercooler, and drain
the liquid out. Chances are, it will be black! Don't
pour this crap into your fuel tank, use it to fill your
camp stove or something.
Now, close the bottom pipe, and squirt some dish detergent
down into the intercooler. Measure out 2 litres of hot
water, and pour that into the intercooler. Let that
sit for a while, and agitate it by blowing into the
pipe if possible. Then drain that out. Chances are,
that will be murky, too!
Inspect the system for any low spots that would trap
liquid, and get the liquid out of there by whatever
means are needed, before you start the engine. Make
ABSOLUTELY SURE there's no standing liquid anywhere
inside, then reconnect everything.
You should be aware that the CCV (crankcase vent) system
is the reason for the gunk accumulating in the intercooler
in the first place. The CCV hose goes from the round
black housing on top of the valve cover and into the
air intake pipe. Pull that hose off the black CCV housing
and check for sticky black gunk inside. If you don't
want to have to clean the intercooler again, and if
it's legal where you live to not have a CCV system,
then you can connect a 3/4" PVC hose to the black
PCV housing and run the hose to somewhere (keep it away
from moving parts and from the exhaust system), and
plug the end of the hose that normally hooks up to the
PCV housing with a 3/4" pipe plug and a hose clamp.
In most areas, this setup is not legal for on-road use,
so you'll just have to periodically clean the intercooler
to maintain peak performance.
Back to Top
Here is another writeup on Intercooler Cleaning: http://www.tdiclub.com/articles/Intercooler_Cleaning/
- Intake Manifold and EGR Cleaning
- This vehicle is equipped with a CCV (crankcase vent)
system and an EGR (exhaust gas recirculation) system.
Oily fumes from the CCV system can combine with carbon
particles from the EGR system to form a black sticky tar
in the intake system. This eventually starts restricting
the amount of airflow into the engine, resulting in gradual
power loss as the vehicle ages and the intake clogging
becomes worse. In rare cases a MIL ("check engine"
light) may be tripped, with an intake manifold pressure
control code set, but normally this does not happen and
no codes are set. Operating conditions, fuel quality,
oil quality, driving habits, and general condition of
the engine all have some effect on how long the intake
system survives before clogging up. It can be prevented
(see section 7.8 below) and this recalibration is highly
recommended for all TDI owners.
But if you didn't do that, and your vehicle is suffering
from lack of power at higher engine speeds at all times,
you need to clean the intake manifold. The following
procedure is generic to all TDI vehicles. Individual
vehicles may differ slightly.
Don't even THINK about cleaning the intake manifold
without removing it from the vehicle ... engines don't
like breathing solid particles.
CAUTION: This is an involved procedure. None of the
steps are particularly difficult but the procedure requires
diligent attention to how everything is disassembled
in order that reassembly proceeds smoothly. Read the
entire procedure before deciding upon whether to attempt
it yourself. If you are not comfortable with the procedure,
then arrange for it to be done by someone qualified.
Expect to pay for several hours of shop time in that
case, because that's what will be required.
7.g.1 Remove the top engine cover. Since it may be
necessary to access some bolts from underneath the vehicle,
support the front of the vehicle securely on safety
jack-stands and remove the lower engine cover.
7.g.2 Disconnect the small-diameter black vacuum hose
from the silver EGR diaphragm.
7.g.3 On A3 and B4 vehicles, remove the screw that
attaches the upper and lower intercooler pipes, unplug
the temperature sensor located on the upper intercooler
pipe, disconnect the small diameter hose from the upper
intercooler pipe, unclamp both ends of both pipes and
remove them from the vehicle.
7.g.4 On A4 vehicles, unclamp and disconnect the upper
intercooler pipe from the intake manifold adjacent to
the EGR diaphragm and valve, and remove the rubber elbow
from the vehicle.
7.g.5 On A3 and B4 vehicles, remove the bolt that attaches
the turbo intake pipe to the intake manifold. Release
the hose clamp that attaches the turbo compressor outlet
pipe to the turbo outlet, and pull the metal turbo compressor
outlet pipe out of the vehicle. Cover the turbocharger
so that no dirt can get into it.
7.g.6 On vehicles not equipped with an EGR gas cooler,
unbolt the EGR transfer pipe at both ends (exhaust manifold
and EGR valve), and remove it from the vehicle. On vehicles
equipped with an EGR gas cooler, unbolt and remove the
EGR pipe from the exhaust manifold to the cooler, then
unbolt and remove the EGR pipe from cooler to EGR valve,
then unbolt the EGR cooler from the back of the intake
manifold. Some of these bolts may require access from
underneath the vehicle. Then swing the EGR cooler out
of the way. The coolant hoses may be left attached to
the EGR gas cooler.
7.g.7 On A4 vehicles, disconnect the linkage at the
anti-shudder valve and unbolt the solenoid and actuator
assembly, and detach the EGR / antishudder housing from
the intake manifold. It may prove easier to leave the
solenoid and actuator devices connected to the vehicle
but hanging loose. Remove the EGR / anti-shudder valve
assembly from the vehicle.
7.g.8 Remove the 6 bolts which secure the intake manifold
to the engine. It will be necessary to bend a heat shield
on the exhaust manifold out of the way to remove the
2 right-most bolts; this can be done with carefully-placed
hits with a hammer on a long screwdriver. On some models,
it will be necessary to remove the oil feed line to
the turbocharger in order to access one of the bolts.
The fitting at the turbocharger will probably be seized
and will let go with a sharp "crack" upon
applying firm pressure. Use a wrench which fits well
over the fitting so that it doesn't slip. Cover the
oil feed to the turbo, and protect the oil pipe, so
that no dirt can enter either component.
7.g.9 Remove the intake manifold from the vehicle after
confirming that nothing else is in the way.
7.g.10 The intake manifold can be cleaned out by a
number of methods. Paint remover, acetone, and other
solvents can be used to soften the goop. (Do this away
from anything that may be damaged by the nasty solvents
and away from any ignition sources due to their flammable
vapours!) A high-pressure washer is useful. Bead-blasting
has also been used but make sure all the beads are out
of there before re-installing the manifold on the engine.
7.g.11 Debris also accumulates in the inlet ports of
the cylinder head, but these are very difficult to clean
without getting too much debris into the engine. One
method that has been suggested involves placing cotton
balls just inside the ports, cutting a bevel in the
crud so there is not such an abrupt transition, and
sucking the balls and cut-off bits of crud out with
a shop vacuum.
7.g.12 Assembly is generally the reverse of removal.
If you had to remove the turbo oil feed line, make sure
you reconnect it, and don't over-tighten the fitting
at the turbo. It will not be possible to get a torque
wrench on most fasteners, so use common sense when re-installing
the bolts. You don't need a new intake manifold gasket.
Back to Top
Solving the "Slow-down Shudder"
and Other Shudder Issues - Recalibrating the Fuel Quantity
at Idle -
A VW specific scan tool such as VAG-COM
is required for this procedure. With the engine warmed
up and running at idle in neutral with all major accessories
such as air conditioning turned off, connect the scan
tool cable and start the scan tool software. Select
engine control module. "Login" using 12233
as the access code. Select "adaptation" and
go to adaptation block 1. Note that the display shows
a default adaptation value of 32768 and shows the amount
of fuel being delivered in milligrams per stroke. (If
it does not show this, you are either on the wrong screen,
or you have an older ECU that differs slightly - see
next paragraph.) The specification range for reported
fuel delivery at idle is 2.2 to 9.0 mg/stroke and they
normally run best between 3.0 and 5.0 mg/stroke (highly
tuned non-stock engines may differ - you'll have to
experiment in that case). If you see a number smaller
than your desired range, enter an adaptation number
that is slightly smaller (say 100 units smaller than
where it is now) and "test", to see the effect.
Adjust the adaptation number up or down as required
to achieve a reported fuel injection quantity as close
as possible to your target. It is only possible to adjust
within a very limited range using this method but experience
has found that it doesn't take much change to make a
big effect in the shuddering. Once you get a proper
setting, "save" it.
Note for '96 Passat and possibly other older ECU
variations: The adaptation numbers are in a different
range, and you won't be able to get feedback on what
you are doing on the same screen. You'll have to flip
between "measuring blocks" group 1 and "adaptation"
block 1 to see what's going on.
Physical adjustment of the upper section of the pump
is also possible to recalibrate the fuel quantity
but it is strongly recommended that the adaptation
method be used first. The physical adjustment method
requires the use of a special tool to loosen the special
security bolt on the injection pump, then the other
3 bolts that secure the top 2 sections of the pump
to the housing (you can leave the upper cover in place
- it's movement at the second split that you are after).
In addition, this method still requires the use of
VAG-COM to ensure that the injection quantity remains
in the proper range. THIS METHOD IS NOT RECOMMENDED
FOR BEGINNERS. It is a "last resort" to
solve an engine that persists in not running correctly
despite all other attempts, and which has had major
surgery performed on the injector pump, and even then,
ONLY if a VAG-COM check finds that the pump is out
of OEM specifications (2.2 to 9.0 mg/stroke at warm
idle in neutral with all accessories off). CAUTION:
Improper physical adjustment of the pump is capable
of causing an "engine run-away" condition
which will result in severe engine damage. ALWAYS
ensure that if a physical adjustment is done, that
the adaptation setting for group 1 is at factory default
and that after completion of all work, the reported
quantity at idle is within factory specifications.
- Engine Power Supply Relay
a.k.a. "Relay 109" Replacement - this is
a very inexpensive part - about $20, and it is easy to
replace yourself. On older models, it is located on the
fuse panel, which is behind a cover on the bottom left
corner of the instrument panel. The cover can be removed
without tools and the relay can be pulled out of the fuse
panel (note the location on the panel and the orientation
of the pins on the relay for reference during installation
of the new relay). On later models, it is located on the
relay panel, which is behind a cover left of the steering
column behind the instrument panel, which will require
a Torx screwdriver to remove. Once the panel is removed,
the replacement procedure is the same as for the older
Back to Top
- Avoiding the Need for Intake Manifold
Cleaning - Recalibrating the EGR System - this vehicle
is equipped with a CCV (crankcase vent) system and an
EGR (exhaust gas recirculation) system. Oily fumes from
the CCV system can combine with carbon particles from
the EGR system to form a black sticky tar in the intake
system. This eventually starts restricting the amount
of airflow into the engine, resulting in gradual power
loss as the vehicle ages and the intake clogging becomes
worse. In rare cases a MIL ("check engine" light)
may be tripped, with an intake manifold pressure control
code set, but normally this does not happen and no codes
are set. Operating conditions, fuel quality, oil quality,
driving habits, and general condition of the engine all
have some effect on how long the intake system survives
before clogging up. It can be prevented and this recalibration
is highly recommended for all TDI owners.
A VW specific scan tool such as VAG-COM is required
for this procedure. With the engine warmed up and running
at idle in neutral with all major accessories such as
air conditioning turned off, connect the scan tool cable
and start the scan tool software. Select engine control
module. "Login" using 12233 as the access
code. Select "adaptation" and go to adaptation
block 3. Give the accelerator pedal a quick "blip"
to ensure that the EGR remains turned on for the next
minute while you perform the following steps. Note that
the display shows a default adaptation value of 32768
and shows approximately 250 +/- 20 mg/stroke of air
intake volume. (If it does not show this, you are either
on the wrong screen, or you have an older ECU that differs
slightly - see next paragraph.) If all is well, enter
33768 as the new adaptation value, and select "test".
Note that the displayed air intake volume changes, usually
to about 370 mg/stroke. The specification limit is 370
mg/stroke, so if you want to remain within OEM shop
manual specifications for emission control reasons,
you might have to enter a number slightly smaller than
33768. (If you don't care about road-legal NOx emission
limits then leave it at 33768. [Depending on the usage cycle, NOx at this
setting can be increased by as much as 40%])
If all is well and you
have a seting that you are happy with which results
in an intake air volume of 370 mg/stroke or just a hair
less, enter "save". Now your intake manifold
either will never clog, or will take so long that the
engine will wear out first.
Note for '96 Passat and possibly other older ECU variations:
The adaptation numbers are in a different range, and
you won't be able to get feedback on what you are doing
on the same screen. The EGR adaptation number for a
'96 Passat with the original "BK" ECU is 188
rather than 33768 and you'll have to go back to "measuring
blocks" group 3 to see the effect before "saving"
the new setting.
As for warranty, no one has mentioned any problems nor should there be. This
adjustment is also completely reversable should one be concerned.
Most provinces and states that do emissions testing on diesels,
just check opacity, so this will not be a factor when testing.
Back to Top
- Setting the Injection Timing
- Injector Pump Mechanical Adjustment - A VW specific
scan tool such as VAG-COM is required for this procedure.
It cannot be done by any other method. The mechanical
adjustment technique used for previous generations of
VW diesels, which used a mechanical fuel pump without
electronic control, is not suitable for the electronically
controlled TDI injector pump.
With the engine warmed up and idling, connect the diagnostic
tool, and select the engine control module. At this
point, one of two different procedures is necessary,
depending upon whether you have the proper factory service
manual for your particular vehicle.
If you have the factory service manual, select "Measuring
Blocks", group 0, then select "Basic Settings".
The glow plug indicator lamp will begin flashing at
this time (this is normal). Do NOT forget to go into
"Basic Settings" because this procedure is
completely invalid if measurements are taken outside
of "basic settings". Take note of the 2nd
and 9th numbers in the display. Locate the chart in
the factory service manual which shows the proper relationship
between these two numbers. Go across the chart with
the 9th number then up the chart with the 2nd number
and make sure it is within the shaded area. It has been
found through experience that these engines have better
cold starting characteristics if the setting is within
the upper half of the shaded area. If it is good ...
don't do anything further. If the second number is below
the recommended range, you need to make a mechanical
"advance" adjustment (see below). If the second
number is above the recommended range, you need to make
a mechanical "retard" adjustment (see below).
If you don't have the factory service manual, select
"Measuring Blocks", and go to group 4. Do
NOT use "basic settings" for this method.
The displays show the requested injection timing, the
actual measured injection timing, and the duty cycle
of the advance solenoid. At warm idle in neutral, requested
timing should be between 0.4 and 2.0 degrees BTDC. If
the actual timing is not more than roughly 3.0 degrees
BTDC, and the duty cycle of the advance solenoid is
not more than 10%, the timing is good ... don't do anything
further. If actual timing is more than 3.0 degrees
you need to make a mechanical "retard" adjustment.
If the duty cycle is more than 10%, you need to make
a mechanical "advance" adjustment.
If you have an A3 or B4, you need to rotate the body
of the injector pump "forward" to retard the
timing and "backward" to advance the timing.
Stop the engine. Remove the upper timing belt cover.
Rotate the engine by hand (shifting trans into 5th gear
and pushing the whole car works) such that the two nuts
at the rear and bottom of the injector pump flange can
be reached through the access holes in the pump pulley.
Loosen these two nuts by 1 turn, loosen the bolt at
the top front of this flange 1 turn (accessed from outside,
not within the pulley). Loosen the bolt located at the
opposite end of the pump below the four injector lines.
With a 17mm wrench, loosen by 1/2 turn the injector
lines on the end of the pump. Now you can rotate the
entire pump housing in the required direction (make
VERY SMALL adjustments) then tighten and reassemble
everything and recheck the timing.
If you have an A4, you need to remove the upper timing
belt cover and adjust the relationship between the inner
and outer parts of the injector pump pulley. To advance
the timing, the inner part of the pulley (together with
the pump shaft) needs to move "forward" with
respect to the outer part of the pulley. To retard the
timing, the inner part needs to move "backward"
with respect to the outer part. The 3 bolts which secure
the two parts of the pulley together may or may not
be "stretch bolts" that must be replaced every
time you do this ... so it's a good idea to get 3 new
bolts just to be sure. Make all the adjustments using
the original bolts, then replace the old bolts with
the new bolts and torque them one at a time.
Back to Top
- MAF sensor - checking and
replacement - With VAG-COM, confirm that in measuring
blocks 3 with the engine at warm idle in neutral with
all accessories off, the requested and actual airflow
rates closely match each other (specifications: 230 to
370 mg/stroke) until the engine has been idling for a
couple of minutes, after which the reported airflow should
increase to approximately 480 (plus or minus about 30)
mg/stroke. At 3000 rpm full load (test can only be done
while driving) the reported air intake quantity should
be at least 800 mg/stroke. If your sensor does not pass
these tests and the intake system is known not to be excessively
clogged, replace the MAF. The Pierburg MAF cannot be used
as a replacement for a Bosch, but a Bosch MAF for a 2.0
gasoline engine vehicle will work fine in a TDI and may
be a lot less expensive...
Back to Top
All information Copyright © 1996-2002
All rights reserved. This FAQ (Frequently Asked Questions)
may not be reproduced without written permission.
Back to FAQ Index