update on boost problems

Dan Simoes dans at audifans.com
Wed Jun 12 09:00:18 EDT 2002

I actually sent this note last night but fell asleep at the keyboard and
accidentally cancelled the email :)

My boost problems continue.  I have an analog gauge installed, good
vacuum, and can regularly see 11-12psi in 4th or 5th gear.  The problem
is that boost is erratic in other gears, sometimes as much as 10psi in
2nd, often only 7 though (1.3 bar).
Even in 4th/5th, climbing a long hill, I can see boost swing from 11 to
7, back to 11, back to 7, and so forth.

I ran with the MFTS unplugged last night, it ran almost exactly the
I checked vagcom data before doing this, with it unplugged, and again
after plugging it back in.

Here are fields from before unplugging, and when it was plugged back in:

215    024-25    80-83    126    095    136    059    128-130    121
217    025          79-81    126-130    097    133    054    125
129    36

The only problems I see are field 7 on the first run, indicating a
possible air leak according to Bentley (should be 41-55 range) but it's
fine on the 2nd run.
And field 6 (idle load) is above the normal range too, which is 123-127.

To my surprise the MFTS is reporting 217 on the second run, showing it
is having a problem.  I will probably replace it just for the heck of
it, as well as the ecu coolant temp..

The O2 sensor is working properly according to fields 8 and 9, I

I have replaced at this point:
- 02 sensor
- plugs
- wires
- cap
- bypass valve
- WGFV (first used, then new).  I did use the H part so there is a
slight chance the hoses are wrong, but I don't think so.
-checked for leaks (pressure test, ok)
- ran lubromoly and techron cleaners
- checked throttle switch and pot
- checked ecu temp sensor and continuity to the ecu.

Where do I go next?  Thanks for your suggestions.
Special thanks to SJM who has been guiding me along via email.

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