[s-cars] Low boost when engine is warm- please help!

[calvinlc at earthlink.net]

Taka,

With a hard problem like this I guess I would try to get ahold of a portable
oscilloscope or a multimeter that measures duty cycle and tap into the
wastegate control signal.  Compare the duty cycles when you are cold and
everything is working properly to when you are warm and boost isn't getting
up to full.  You could then isolate between a problem not allowing the car
to get to full boost mechanically or a problem with the computer not
commanding it to full boost.  If it is the computer then check each and
every sensor's signal with the O-scope while driving (two person job
preferably).  If it is not then I would start by swapping the WGFV with a
known good one.  Good Luck!

--Calvin



-----Original Message-----
From: s-car-list-bounces at audifans.com
[mailto:s-car-list-bounces at audifans.com]On Behalf Of TM
Sent: Saturday, September 04, 2004 12:32 PM
To: s-car-list at audifans.com
Subject: [s-cars] Low boost when engine is warm- please help!


Any further help on this problem?

Quick recap:
Car runs fine when cold, drops to 10 psi peak when warm, can see short
peaks above 10psi, but they quickly get throttled back. This ONLY
happens
when the engine is warm- past the 2nd hash mark from full cold.

I replaced the multifunction temp sensor on the water manifold
and the engine coolant sensor on the back of the head- nothing has
changed either
time. Previously, I had an engine coolant sensor fault code.

Now that I've checked codes, there are none.

For the duration of the testing, I'm running Sunoco Ultra 94.

Car has sat with the battery disconnected for about a week at a time
between testing.

I'm going to look at the wastegate frequency valve and the throttle
potentiometer
next.

This problem is driving me nuts- all the more reason to get a C5 Vette,
soon!

Taka
150hp turbo quattro, used to be 265hp

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