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engine stalls with ac on after driving a few minutes 900 1994

First post here we go! I have a 94 945 with 228000 that I have had for 2 years now. Recently after driving with ac on for 10 to 20 minutes engine will try or will stall. Sometimes it will restart immediately if ac off sometimes not until later after cooldown. NO stalling or running problems at all if I leave ac off. I have put 30,000 miles on it in 20 months. I bought this car to ease my pocket book from my thirsty diesel truck. New Items in past 2 years,plugs, plug wires, rebuilt injectors(with new 4 hole nozzles, WOW what a difference),coil, dist cap and rotor, timing belt, battery(recent), O2 sensor 1month ago, all vacumn lines, power amplifier(that thing behind air filter box on driver fender), crank position sensor, injection temp sender, heat guage temp sender, new flame trap, cleaned throttle body, rebuilt idle air controll valve(after trying to clean old one with obvious failure should have left it alone). I do all my own diagnosing and work, and with help of brickboard and chiltons Ive learned the volvo and feel comfortable working on it, but now I am stumped! Help please! NO Codes are stored after engine stalls, but all lights come on, but go off after restart go figure. Engine runs like a top with great idle and no hesitation. Oh it is a bosch ignition system not the regina. Had a 92 940 gl cherry with only 90,000 untill I let my dad borrow it and he thoughtfully redecorated the front end with rear end of another car which resulted in a total but bought for salvage to have good parts car since drivetrain hardly broken in for a volvo.








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    engine stalls with ac on after driving a few minutes 900 1994

    Howdy, TXTREEFROG.

    Holy Cow. Excellent first post, man! Straight to the point with a lot of relative information. I would suggest that you break up your thoughts with paragraphs to make it easier to follow. Other than that, a near perfect request for information.

    It never offers to stall with the AC OFF? And, it sometimes is HARD to START after a stall? Interesting set of symptoms.

    Let's start with the AC. Have you had it serviced recently? Is it possible the compressor is seizing? Are the belts glazed? If the belts are glazed it is possible that they are slipping at higher RPM and the sudden load as they catch on the pulley when RPM falls cannot be compensated quickly enough to prevent a stall. That, however, does not explain the HARD START condition.

    Another possibility is an AC related vacuum leak. But that would manifest as a high idle when the car is restarted after a stall.

    I am pretty sure that there is a logical AND situation with AC ON and IDLE that causes the ECU to bump idle speed up to compensate for the load of the compressor. Is that circuit working? Basically it should be the idle switch at the throttle and another switch somewhere in the compressor clutch circuit; don't take that as gospel, I haven't got a '94 940. There may be more than simple switching involved.

    Have you got a schematic for your car? If not, see http://www.volviki.org/tiki-file_galleries.php for a copy of the Mitchell's wiring diagrams.

    Post back to let us know how this progresses. And, welcome aboard.

    --
    Mr. Shannon DeWolfe -- I've taken to using mister because my name misleads folks on the WWW. I am a 53 year old fat man. ;-)







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