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Engine cut-off during warm-up

Discussion in 'Boxers/TR/M' started by TestaDDS, Aug 24, 2025 at 4:51 PM.

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  1. TestaDDS

    TestaDDS Karting

    Sep 6, 2015
    97
    France
    Full Name:
    RM
    #1 TestaDDS, Aug 24, 2025 at 4:51 PM
    Hello,

    I’m reaching out because my Testarossa (1989, KE-Jetronic without catalytic converter, fuse board replaced) is giving me an issue that I can’t diagnose. During its warm-up phase it suffers from engine cutouts (2 to 3). It restarts without any problem, but it’s quite disturbing in traffic. To be precise, it doesn’t stall with a drop in RPM, it just cuts off abruptly. Once it’s fully warm, there are no more cutouts and everything runs normally. I’ve checked a few ignition circuit connections without success.

    If you have any ideas, I’d be grateful.
     
  2. turbo-joe

    turbo-joe F1 Veteran

    Apr 6, 2008
    9,573
    southwest Germany, France ( Alsace ) and Thailand
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    romano schwabel
    #2 turbo-joe, Aug 25, 2025 at 12:04 AM
    you are sure it comes from ignition? may be fuel pumps stop? but when the engine stop rapidly it is a sign for the ignition. if fuel problem it would first change the rpm a little before stopping.
    when it just start again after stalling and then you test the connections you can not find anything because it will run again.
    so try to test with a multimeter if you have on both coils 12 V power when the engine stop.
    does this problem exist also when warming up the engine in idle, so without driving or only when driving/trying to drive?
     
  3. TestaDDS

    TestaDDS Karting

    Sep 6, 2015
    97
    France
    Full Name:
    RM
    #3 TestaDDS, Aug 25, 2025 at 1:21 AM
    Thanks for your reply, TurboJoe.
    The cutouts happen both at idle and while driving.
    I’ll check the coils, but if I lost one, one bank of cylinders would still be running, right ?
     
  4. turbo-joe

    turbo-joe F1 Veteran

    Apr 6, 2008
    9,573
    southwest Germany, France ( Alsace ) and Thailand
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    romano schwabel
    #4 turbo-joe, Aug 25, 2025 at 2:00 AM
    that is right, if it is the coil what is the problem. but I think both coils at the same time never will fail.
     
    TestaDDS likes this.
  5. Rifledriver

    Rifledriver Three Time F1 World Champ

    Apr 29, 2004
    37,244
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    Brian Crall
    #5 Rifledriver, Aug 25, 2025 at 6:41 AM
    Not correct. One coil module triggers fuel pump operation so when it fails car will not run. Never seen the coil modules be temperature sensitive.

    If it is that predictable it should not be hard to track down. Start it cold with a fuel pressure gauge and a timing light hooked up and see which stops working.
    Diagnosis on a repeatable problem is generally very easy. Be methodical and quit trying to identify the exact component responsible.
     
    NYC Fred likes this.

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