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Thread: fast idle 911s

  1. #1

    fast idle 911s

    can someone help? l have a 1971 911s with a 1974 2.7 210 hp MFI engine that I purchased in Rotterdam some 16 years ago.A great car to say the least, all most trouble free.however over the last year it started idling fast?when the engine is could it idles fine, but when it warms up it idles fast, about 1400 rpm .Were should l be looking?

    thanks Rick

  2. #2
    Roland Kunz

    best to start is with the valve lash, the dwell angle and the timing.
    If everything is proper then we look closer at the MFI.

    hang out the short throttle links and the throttle link to the MFI pump. to find out if the problem is the throttle linkage or the Butterfly/Pump base adjustment. Then check for vacuumleaks/worn shafts at the butterflys.

    Basically the links should be 114 mm between MFI pump and main linkage crossbar, 150 mm each downlink to the butterflys and 275 mm from the intersection rod between the rear link moving down to the trany and the main linkage crossbar.


  3. #3
    Hi Roland,thanks for the info, l thought it might be something like a solenoid if that engine has one?why does it idle just fine when the engine is cold about 900 rpm , but when it warms up the idle speeds up?
    thanks Rick.

  4. #4
    Roland Kunz

    First rule on MFI is to touch it as the last unit if every thing else is proper.
    Now the problem can be your pump but you need to know how it works and which way you can work on it.
    Best way is to set your idle warm and adopt the warm up.

    And just read some stuff


  5. #5
    fantastic info Roland, it's going to take some time to digest,hopefully I'll be able solve this fast idle problem.
    thanks again regards Rick.

  6. #6

    fast idle

    One think you might try is gumout Fuel injector cleaner if it ran good before the problem try running the heavy duty stuff through it two tanks otta do it my 71 started acting up and all it was dirty injectors and pump you should do this once year, everyone kept recomending sending the pump in, and didnt make senses after talking too pacific FI rebuilders I tried this and it worked I have tried just about every cleaner on the market and the gumout extra heavy Duty was the most effective and cheap 2.00 or less. Good luck

  7. #7

    Re: fast idle

    thanks bud , i,m going to give it a try ,often thought about it but never tried it

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