[200q20v] Lack of boost very puzzling... long winded question

Phil Rose pjrose at frontiernet.net
Wed Mar 21 10:45:04 EST 2001

Sounds as though you've been rounding up the appropriate "usual 
suspects". Tom's reply about his idle switch-replacement cure prompts 
me to ask if you've ever at least done the recommended _adjustment_ 
of the idle switch. Although one the two screws that need to be 
loosened is not so easy to reach, I believe that the basic adjustment 
is straightforward (just rotate the switch fully in the direction 
indicated in the Bentley procedure--I forget whether it's CW or CCW). 
That was done on my car just before delivery to me and fixed a 
low-boost symptom.


At 10:20 PM -0600 3/20/01, Cordeiro, Alan wrote:
>Hi everyone,


>The only code that occasionally reappears is the idle switch, sometimes
>it takes two or three days for this code to re-appear. I have put a
>meter across the throttle position potentiometer, and watch it run smoothly
>from 0.3 to 4.7 volts. I also checked the engine temp sensor and the
>multifunction sensor was replaced by me to fix a "too low" temperature
>reading after I replaced the thermostat with no noticeable improvement
>in running closer to normal engine temperatures.
>I have measured the output of the altimeter, it sits just over 4 volts,
>seems about right for the Michigan area. By temporarily putting in a much
>stronger spring, the gauge goes to 1.9 almost right away and the boost
>shuts me down, so the turbo is just fine. (It spools right up to 1.3 almost
>as soon as the rpm gets over 1500, another good indication).
>I have a 1.2 watt lamp across the wastegate solenoid, and watch the lamp
>glow solid when I floor the loud pedal. Around 1.3 it begins to flicker
>and by 1.5 it is pretty much totally off, eliminating all further boost.
>So it would appear the CPU feels that for some reason it should limit the
>boost to 1.5. BTW the gauge seems right, it reads 0.9 or 1.0 when I first
>turn on the ignition, and runs 0.5 to 0.6 at idle, 0.7-0.8 cruising at
>"typical freeway speeds".
>I am using 93 octane, but I have experimented with lowering it to 87
>just to see if the boost control point goes down some more, but it has no
>effect. And the dash (added) check engine light never comes on after
>the engine starts, and there is no evidence of knocking (even when I
>put in 87 octane).
>Any ideas, does this ring a bell with someone???
>'91 200q20v, 150k
>200q20v mailing list
>200q20v at audifans.com


Phil Rose
Rochester, NY
mailto:pjrose at frontiernet.net

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