PLEASE NOTE THAT THIS FAQ IS OUT OF DATE.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 ( in the mean time for more updated information.

I'd like to send out a thanks for Jon Bartlett for his time and effort in creating the original FAQ. This expanded version was compiled by GoFaster, Skypup, TooSlick, Jimmy, ThinkDiesel, and Jonathan Bartlett.

This is basically a summary for the frequently asked questions from the TDI Forums on Fred's TDI page (  No guarantee is made for the accuracy of this document, so use at your own risk. Also these are peoples opinions, so please use your own common sense and judgment when reading these statements and others found in the TDI Forums.


August 29, 1998: original by Jon Bartlett

January 16, 2000: updated by GoFaster, SkyPup, TooSlick, Jimmy, ThinkDiesel, and Jonathan Bartlett

June 21, 2002: Sections 7 & 8 updated by GoFaster.

September 30, 2002: Sections 6 updated by GoFaster.

October 18, 2003: Section 5 updated by wxman.

For a more printer friendly version in Adobe Acrobate version download/view TDIFAQ.pdf (Feb. 27, 2003).

Besides this document, some of the more common questions have been archived on the forums in the FAQ section available here:

Last updated:  June 10, 2003

1) How It Works

a. Do I need to read this?
b. General
c. Improvements over Previous Diesels
d. Fuel System
e. Air Intake System, EGR, PCV
f. Engine
g. Turbocharger
h. Engine Controls


2) General FAQ

a. Types of TDI Engines
b. Cold Starts
c. Warm-up
d. Shifting Gearse. Performance
f. Noise, Vibration, and Smell
g. Longevity and Reliability
h. Fuel Consumptioni. Fuel Availabilityj. Maintenance Costs
k. Can I use a remote car starter?l. Where do I find a good mechanic?
m. Venting
n. Things you may not know, but should
3) Fuel

a. specifications
b. cetane
c. winterized d. low sulfur
e. non-taxed (off road)
f. bio-diesel
g. additives
h. refueling

4) Oil
a. specifications
b. semi and full synthetic
c. additives
d. consumption
e. where to get
f. I just changed the oil, and it's still black. Why?
g. Can I get the oil changed at a quick-lube place?
h. Synthetic oil is too expensive. Can I mix it with regular oil?
5) Emissions
a. TDi vs. gasoline
b. bio-diesel
c. California and New York issues
d. The future - Tier 2
e. emissions testing
6) Performance

a. A General Introduction to Diesel Engine Performance with a Historical Perspective
b. Limiting Factors to Diesel Engine Power Output
c. Before You Modify ...
d. Common questions and answers before proceeding further ...
e. Discussion of Popular Engine Modifications
    1.The Chip (Chipping)
    2. Tuning Boxes
    3. Bigger Injectors
    4    a. Boost Control System Modifications - A3 and B4 cars with GT15 or KO3 turbochargers
          b. Boost Control System Modifications - A4 cars with VNT turbochargers
    5. Air Intake System Modifications
    6. Exhaust Modifications
    7. Intercooler Modifications, Intercooler Duct Modifications
    8. Advancing the Injection Timing
    9. Bigger Turbo
    10. Camshafts
    11. Blow-off valves or BOV or similar
    12. Nitrous Oxide
    13. Propane Injection
    14. Sensor Tweaks and Various Home-grown Mods
    15. Turbo Timers
f. Trailer Towing Issues
g. Fuel Consumption
h. Suspension
i. Brakes
j. Driveline
1. Clutch
2. Final drive and differential

7) Maintenance

a. Engine Oil and Filter Maintenance
b. Fuel Filter / Water Separator Maintenance
c. Air Filter and "Snow Screen" Maintenance
d. Timing Belt Inspection and Replacement
e. "Supplementary injector" on 1996 Passat TDI models - North American specification only
f. Intercooler Cleaning
g.Intake Manifold and EGR Cleaning
h. Avoiding the Need for Intake Manifold Cleaning - Recalibrating the EGR System
i. Solving the "Slow-down Shudder" and Other Shudder Issues - Recalibrating the Fuel Quantity at Idle
j. Engine Power Supply Relay a.k.a. "Relay 109" Replacement
k. Setting the Injection Timing - Injector Pump Mechanical Adjustment
l. MAF sensor - checking and replacement

8) Troubleshooting
a. Preventing Future Problems (to the extent possible)
b. Engine will not start, or engine is difficult to start.
c. Engine stalls randomly without warning and may or may not restart
d. MIL ("Check Engine") light is on while driving, or "glow plug" light is flashing while driving
e. Engine lacks power - "No Boost" - "No Turbo" - "Can't hear turbo"
f. Fuel consumption seems high
g. Oil consumption seems high. Other problems which are apparently lubrication-related are also covered here.
h. Oil leaks onto ground
i. Smokes on cold start-up
j. Smokes under full acceleration
k. Smokes from exhaust under other conditions
l. Bucks and snatches slightly at low speed when cold
m. Rattles, buzzes, and resonances from the exhaust system
n. Accidentally filled tank with gasoline - now what?
o. "Shuddering", "misfiring", "stumbling" at highway cruising conditions
p. "Surging" during acceleration; fluctuation of turbo boost pressure.
q. Hesitation upon moving away from a standstill or upon sudden application of accelerator pedal
r. Miscellaneous Strange Noises and Odd Behaviour

9) Non-Volkswagen TDi

10) AMTS. pour point temperatures for winter diesel


All information Copyright 1996-2003 Fred Voglmaier.
All rights reserved. This FAQ (Frequently Asked Questions) may not be reproduced without written permission.

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