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A
Sluggish Bug
Eric Seifert, Automotive Technical
Editor
A customer recently noticed that his 2002 VW
® Beetle ® turbo diesel had lost its pep. After he scheduled
an appointment, I went to work researching the symptom he described.
Perform repair steps 1 through 9; if any of
these steps reveals a problem, repair or adjust as necessary and
perform a road test prior to continuing on to step 10. All steps
should be documented using VAS® 5051/5052 (or equivalent) printouts
(if related to warranty claim).
A Hand Vacuum Pump may be required to diagnose
the problem.
Applicable Vehicles:
98-03 New Beetle ® with1.9L TDI (ALH)
99-03 Golf ® and Jetta ® with 1.9L TDI (ALH)
01-03 Jetta Wagon ® with 1.9L TDI (ALH)
Repair Procedure:
Review safety procedures in ALLDATA®diy.com before beginning.
 ECM
ground connection.
Inspect ECM ground (GND) connection for corrosion, poor or no
connection.
- Injection pump timing.
Check start of injection pump timing.
Tip: An
adjustment to the upper range is advised.
- Snow screen (if applicable) at intake air
duct.
• Check snow screen, located
below left front fender in air duct (3), and clean as necessary
• Inspect air cleaner element
(1) for proper installation.
• If air cleaner element is
deformed due to improper installation, this may cause the MAF
sensor to fail.
• Replace
air cleaner element as necessary.
Tip: Always
check with VW or your local supplier for latest part revisions.
 Vacuum
hoses.
Check integrity of all vacuum hoses and connections, and repair
as needed.
- EGR valve and intake manifold air flap (integrated
in EGR valve).
• Remove intake hose (1) at
EGR valve
• Remove vacuum hose from
EGR valve (2).
• Connect hand vacuum pump
to EGR valve (2).
• Apply vacuum and make sure
that air flap (arrow) opens and closes freely.
If flap does not open and close freely:
• Replace
EGR valve / flap.
Tip: Always check
with VW or your local supplier for latest part revisions.
 MAF
sensor and EGR valve including solenoid valve.
• Check
correct function of MAF sensor and EGR valve including solenoid
valve.
Tip: Since
both systems work closely together, if one system malfunctions
it will directly affect the function of the other. Therefore it
is important to follow the procedure carefully.
• In
addition, the MAF sensor must be full-load tested.
If MAF sensor readings are out of tolerance (even if no
MIL ON condition or DTC is present), before replacing MAF sensor
or EGR solenoid valve:
• Ensure
wiring is OK and electrical connections are clean and functioning
properly.
If wiring is OK and electrical connectors are clean and functioning
property:
Replace MAF sensor
Tip: Always
check with VW or your local supplier for latest part revisions.
• If MAF sensor failed full-loaded
test, and after replacement of MAF sensor full-load value still
cannot be attained:
• Check turbocharger
- Crankcase Ventilation System.
• Inspect and verify that
it is functioning to OEM specifications.
- Engine oil level.
• Check and adjust to proper
level if necessary. DO NOT OVERFILL!!!
- Fuel Quality.
• If
condition occurs suddenly, fuel quality may be inferior
If fuel is suspected to be of poor quality:
• Drain and refill fuel with
known good quality fuel.
- Check for Carbon build-up.
If all previous items are functioning according
to specifications and the vehicle still exhibits poor throttle response,
it may be necessary to physically inspect the EGR valve and intake
manifold as (in higher mileage vehicles) there may be excessive
carbon build-up in the intake manifold and/or EGR valve.
Tip: While some carbon
build-up is normal and not a concern, excessive carbon build-up
is related to fuel quality and soft driving behavior (operation
at low speeds and short driving distances), under extremely cold
and damp operating conditions.
To inspect for carbon build-up:
Remove EGR valve and inspect and record depth of carbon in the valve
and intake manifold.
Normally carbon build-up is not a concern; a
problem may occur only if it is excessive (greater then 10 mm).
If the carbon layer in the EGR valve and/or intake valve is greater
then 10 mm (50% - 60% clogged):
Replace EGR valve and/or intake manifold.
If the EGR cooler is clogged more then 50% -
60% in its flow area:
Replace EGR cooler.
Tip: Always check
with VW or your local supplier for latest part revisions.
If new parts are not available, or if it is
more economical, the intake manifold and EGR cooler can be cleaned.
Tip: Prior to cleaning,
the intake manifold and EGR cooler must be removed from the engine
to ensure that no carbon particles enter the engine.
Written by ALLDATA Technical Editor, Eric Seifert.
Eric is an ASE certified Master Technician and Engine Machinist.
He is a graduate of the De Anza College Automotive Technology Program,
with 20 years of independent shop and parts store experience.
©ALLDATA LLC. All rights reserved. All technical
information, images and specifications are from ALLDATA Repair.
ALLDATA is a registered trademark and ALLDATA Repair is a mark of
ALLDATA LLC. All other marks are the property of their respective
holders.
New Beetle, Golf, Jetta, Jetta Wagon, VAS, VW
and Volkswagen are registered trademark names and model designations
of. All trademark names and model designations are being used solely
for reference and application purposes. |
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