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'91 740T intermittent rough idle, stall 700

Here we go. Bought a '91 740 Turbo (148K) for my son's first car. Ran good for 2 months, then stalled at a stop light (in the rain). 10 minutes later, it fired right up and ran good for a couple weeks, then did it again (in the rain). The problem has gotten progressively worse. It will idle rock solid for 5 or 10 minutes, and then run rough and die. No amount of cranking will restart, unless you use starting fluid. Then it will start and run very rough until you blip the throttle a few times (some dark smoke on the restart), then it will usually settle into a decent idle, and then the whole process repeats. It never stalls on the road. Only at idle. It does have an intermittent miss at highway speeds. It used to stall only when it was wet, but now it does it all the time. Upon stalling, it has spark and the plugs are not wet.

I have cleaned the TB and the Idle Air Control. New cap, rotor, wires, plugs, air filter. One clue: Just before it dies, if I unplug the Air Mass Meter, it will idle better, but will not rev up. When I plug the AMM back in, it stalls.

If I can't solve this soon, I'll part with it, so if anyone is interested in a white 740 with a mint body and good interior, I'll make someone a heck of a deal!!!

Thanks for your help.

Scott








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    '91 740T intermittent rough idle, stall 700

    Scott I have the same problem, have you been able to resolve your stalling
    in wet wether problem???
    Dans








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    '91 740T intermittent rough idle, stall 700

    It's not a real good idea to disconnect AMM when the car is running or the ignition on. Try another AMM, Good luck,rcs








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    '91 740T intermittent rough idle, stall 700

    i forgot to mention before you do anything. read the codes first, both 2 and 6. not all codes will set a check engine light. write them down and reply with that info. no codes, reply anyways. good luck, chuck.








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      '91 740T intermittent rough idle, stall 700

      Sorry, but I don't know what's involved in reading the codes. I can tell you the check engine light did not come on until I unplugged the AMM while it was running. Unhooking/rehooking the battery will turn the check engine light off.

      I found a mechanic that has a couple known "good" used AMM's, and I will beg him to let me try one to see if it solves the problem. That is if I can get the car to him!!! It may go on a flatbed!

      Would it make any sense at all to replace the FPR? Or would it run bad ALL the time if the regulator were bad?

      Thanks for the replies, as I really appreciate the help.

      Scott








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        '91 740T intermittent rough idle, stall 700

        see the faq's about pulling the codes.

        the fuel pressure reg MIGHT be bad but it won't affect the way the car runs with the amm unplugged, that's the biggest clue. i'd get a fuel pressure test first.

        i'm curious, did the car run any different when you reconnected the battery? good luck, chuck.








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    '91 740T intermittent rough idle, stall 700

    the car will never accelerate with the amm unplugged. the fact it runs better at idle sounds like the amm is bad. if you want to test it, lemme know, my notes are at work. or, you can borrow a known good amm and try that. good luck, chuck.








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      '91 740T intermittent rough idle, stall 700

      My 91 740T had similar sounding problems. After replacing the common items like FPR, relay, etc, it was found to be the connection on my main fuel pump was loose. After cleaning and crimping and firmly plugging in the connections the problem has never re-occured.

      You never know...

      Sean







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