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Cleaning cold start idle valve did not work (1991 740) 700 1991

You will recall, the car would start up right away, but there was no high idle to keep the car running as it warmed up. I removed and cleaned the valve as Randy and others recommended.

The problem is still there, but now I understand a little more about when it happens. When the outside temperature is below about 32 degrees, there is no fast idle upon starting. When the outside temperature is above 32 degrees, the fast idle works normally with no problems. Any ideas?

A new problem: Three days ago, a new and different problem, a warm idle problem, developed. Any time after the engine is fully warmed up, if I put the gear selector in Neutral or Park, the idle starts acting erratically and the RPM dial bounces around. Under normal conditions, when the car comes to a stop in Drive, the idle drops to it's normal 700 or so RPMs. Again, under normal operation, if you then shift into Park or Neutral, the idle with go up to 1000 for a second or two and then drop down to its normal 700 or so. With the new problem, when you shift into Neutral or Park the idle goes to 1000 like normal, but does not always drop to 700. One of two things happens: If the idle drops below 1000, it idles erratically, jumping back and forth (quickly) between 700 and 1000 and all numbers in between. If after shifting into N or P, it does not drop below 1000, it stays there (at 1000) and starts to slowly increase on its own to 1200 and 1300. Two times, it has gone up to 1500 and 1600. During this time, sometimes the RPM needle is steady and at other times, it starts jumping going up and down erratically (within a 200-300 RPM range). If you put the gear selector in Drive during the erratic high and low idling, the idle goes back to its controlled idle of 700 or 800. So the problem only seems to occur in N and P. Any ideas?

Allan








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    Cleaning cold start idle valve did not work (1991 740) 700 1991

    Agree with usual suspects already posted, I have just purchased a 1 owner
    '91 745 N/A with 192K. Noticed lower than normal cold idle when first started
    but OK shortky thereafter. Problem was large HOLE in underside of intake bellows
    between throttle body. remove thislarge intake hose and check underside at
    curve to throttle body (rubber part deteriorated). needless to say throttle
    body was filthy. After installing replacement bellows and cleaning throttle
    body no more problems (this is on non turbo motor)








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    Cleaning cold start idle valve did not work (1991 740) 700 1991

    I had something similiar in a 91 740 turbo. TP sensor, throttle body was clean, etc. It turned out to be a loopy connection at the temp sensor for ignition/MFI. I just greased the electrical connection & the problem disappeared. I think the resistance changed enough to tell the ECU to speed engine up/down but not enough to trigger a fault code.








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    Cleaning cold start idle valve did not work (1991 740) 700 1991


    Did you clean the throttle body?
    Sounds like crud in the throttle body.
    Check out FAQ's...







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