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1993 940 turbo stalls sometimes on braking/low rpm conditions, still stumped



The car starts and runs fine. Usually. But, after it reaches normal operating temp, if you let off the gas pedal, and brake, or just let off the gas to slow down, you can see the idle drop on the tach to below 400rpm, sometimes. It doesn't try to stall every time you brake or lift off the throttle. And, once it drops below 400rpm, it will usually stall. Unless you anticipate it stalling and put your foot back on the gas. Then, it will rev back up again and not stall. It ALWAYS restarts after stalling.

However, it does not do this every time, but since I finally realized it appears to be a low idle causing the stalling problem, I watch the tach closely on deceleration. 7 out of ten times, the idle will bounce a little below the 500 RPM mark, then stall. According to the FAQ'S the 1993 940 T is supposed to idle at 775+or-. Mine idles at approx 600-650 in park. If it just had a stinkin' idle screw, I could just turn it a little and get the idle back up where it belongs. But nooooooooooo, they had to let the computer control it.

Here is what I have tried:
Checked all OBD codes, and it is not spitting any codes.
Cleaned throttle body
Cleaned Idle control motor. Also swapped it out with a known good one from a perfect running 240 (same part#), still low idle, and stalled again
Changed out fuel inj. relay (before I realized it is idle related)
Changed out RSR relay " " " " " "
Checked every possible spot for a vacuum leak
Changed out AMM with a known good one, still stalled, same symptoms
The car has a new Crank sensor
The car has a new Power stage module

If I unplug the Idle control motor wire, it idles at about 1000rpm and doesn't stall. I have worked long and hard on this, and done lots of searching in the FAQS. Any help would be appreciated.






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New 1993 940 turbo stalls sometimes on braking/low rpm conditions, still stumped
posted by  pittroj subscriber  on Sat May 28 16:16 CST 2011 >


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