[V8] Re-birth of my '90 200 tq
kentmclean at comcast.net
Sun Nov 22 12:30:44 PST 2009
Brian K. Ullrich wrote:
> I do have a couple of issues with the driveability of the car. Two areas
> concern me, and they are likely related.
> First, the idle is a little rough once the car is warm, and it is prone to
> stalling at idle then.
My guesses, and easy fixes, are a bad O2 sensor that doesn't do anything until
the engine is warm, when it's failure is noticed, or a bad/dirty ISV (idle
stabilizer valve). A dirty ISV can be cleaned:
> Second, there is a buck at 1.7 bar. Under that, she boosts well and pulls
> hard, but once I hit 1.7, she bucks until the boost drops below 1.7. I can
> reproduce it at will. This one stumps me.
My thoughts (and they're just that): the turbos have a knock sensor that may be
activating under extreme boost, causing the ignition to cut out. That might make
it buck. The turbos also have something (I forget what; helpful, huh?) that cuts
boost to prevent over boosting. That might make it buck. And last, old/bad
spark plugs or ignition components might underperform at high boost, making it buck.
I cc'd the main list, as they might have more ideas. Good luck with it.
1990 V8 w/5-speed and other mods
1991 200 TQA #3, with mods
1999 A4 Avant, V6 Tiptronic
gone: '91 200 TQA x2, '94 100 S Avant, '89 200 TQ "Bad Puppy"
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