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RE: 91 200q Boost and WG springs (kinda long)

And finally - The only problem observed with the stiffer spring is that
after laying into it in 2nd and 3rd (taking both to near redline), about
2 seconds_after_I back off and resume "normal" driving, I get the check
engine light. Any ideas here? 
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I had the same problem with my car (91 200q, TAP chip and WG spring).
Ivor said the chk eng light would come on with the spring/chip mod b/c
the exhaust flow past the O2 sens was too much for it, and the O2 sensor
thus couldn't get a reading. The check eng light comes on b/c the
computer can't register any readings for the O2 level. Because there is
in fact no problem, the engine still runs fine, though the light comes
on. Ivor's advice: don't sweat it - no fix for it unless you get the RS2
manifold (freer flowing, less pressure, slower exhaust movement, O2 can
read fine).

As far as surging goes, you can try backing off on the allen key
adjustment in the top of the wastegate - you must knock out the cap on
top of it - underneath is an allen head screw that allows for slight
(~1-2 psi) adjustments in pressure. If you feel surging, back off the
allen adjustment. My understanding is surging boost means the wastegate
freq valve is backing off and reapplying as the pressure builds against
the pre-programmed 1.95 bar (?) safety wall.  

You may have a vaccum leak somewhere - How's throttle response at low
RPM? is it sluggish at all (there should be no hesitation when pressing
the gas in neutral)? 

How many miles do you have on the car? How are the plugs, plug wires,
cap and rotor? These are likely minor and not related to your boost
problem, but could cause eng. lite too if any are bad enough to inhibit
proper timing outside of the computers ability to adjust for small
variances. resistance on plug wires is 5k Ohms I think.

I don't have the eng light prob. anymore as my car is now screwed up in
other ways - boost drops off after 5500 RPM from 1.9 down to ~1.7. Used
to got to 1.9 and hold till past redline :) and sometimes 2.0. Now the
car stalls if you wind it up to make a left turn lite and then let off -
it'll drop down to 900 RPM and then dies - not ISV though. Turbo Cut-off
valve checks out too. Can't find any leaks in vac system either. Gonna
have to bend over and let the dealer take a hack at it. Long story
behind it (incompetent mechanics - (no, not me), can't figger it out,
and I'm in the middle of moving right now and swamped at work so it'll
have to wait.

Good luck, HTH


91 200q TAP, Bil/Eib, etc
86 5ktq I.A.

BTW sorry if I didn't respond to your (or others) e-mail lately; two of
my hard drives crashed and I lost all my mail files, thus all messages
dissappeared. Big big headaches! Back in the saddle now, though.