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Thread: M30 running on 3 Cylinders !!! help

  1. #1
    Join Date
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    Default M30 running on 3 Cylinders !!! help

    I don't know what is it and where!! ... the car starts OK .. nothing wrong ... just when I step on the accelerator reaching over 2000 RPM the engine stops the cylinders 2, 4 and 6 -that's if I'm counting cylinder 1 from the radiator - and it wont work again until I stop the engine and start it again ... this problem started today on the high way. before that there was no problem.

    I would like to add a note here. that my alternator doesn't start charging until I rev the engine to above 3000 RPM. I feel that the alternator is noisy or triggering something ... but what is it?! I'm going to try a different DME I just feel that the injectors seas the get the signal.

    Any idea guys ?! I'm puzzled !!

  2. #2
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    Default

    Maybe the dist. cap and rotor?

  3. #3
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    Default I'll fathom a guess...

    ECU problem or injector wiring problem. The motronic batch fires the injectors three at a time. You should be able to match the batch fire sequence to the ECU sequence; if they match I'd suspect the above.

    You may also want to check the sensor wire from the #1 plug. That's the trigger for sequencing the firing batches.

    BTW, how do you know what cylinders are not firing?

    Let us know...curious problem.
    Bellevue WA
    90 535iM - not much stock remains. 3.7 liters, ported head, cammed, 3.73 diffy, M5 brakes, MAFed, yadda yadda yadda
    86 Porsche 951 - Track Toy

  4. #4
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    well ... when it starts vibrating ( running into 3 cyl mode ) I unplugged the spark plugs HT wire one by one .. the ones were not affected was 2,4,6 that tells that there is no gas. also ... the way the engine behaved when I throttled it took a pattern its like it cuts off then on again and it doesn't sound like a choke stall or something like that.

    if it was the sensor that triggers the sequence. I think it shouldn't start correctly then go off sequence right?

    I just can't seem to find a logical explanation yet !! but the it behaves has a pattern !!


    **EDIT: I just came back from a test, I replaced the DME with an old one .. still got the same problem, I disconnected the trigger sensor ( right plug next to the crank sensor ) and the engine behaved much better, not smooth but seems that the DME used the prediction method. but didn't run in 3cyl mode.

    do you think that was it? I reconnected it while engine was running but nothing changed. also gas smell was so obvious and few explosions happened in the exhaust afterwords.
    Last edited by grave77; 02-20-2006 at 10:01 AM.

  5. #5
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    spark is there all the time ... I checked each plug by removing the wire and pluging it back.

  6. #6
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    how do you know how many cylinders its running?

    www.KaRealtySF.com
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  7. #7
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    from the spark plugs wire. when I removed one by one ... only 3 affected the engine ... and the 2,4,6 cylinders were not affected while spark was alive.

  8. #8
    Join Date
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    1,639

    Default Smell of gas would suggest spark problems...

    ...not lack of fuel problems.

    How old are your plug wires? I'm now sort of wondering if you don't have shorts in the plug wires. That can cause intermittant problems.


    Quote Originally Posted by grave77
    well ... when it starts vibrating ( running into 3 cyl mode ) I unplugged the spark plugs HT wire one by one .. the ones were not affected was 2,4,6 that tells that there is no gas. also ... the way the engine behaved when I throttled it took a pattern its like it cuts off then on again and it doesn't sound like a choke stall or something like that.

    if it was the sensor that triggers the sequence. I think it shouldn't start correctly then go off sequence right?

    I just can't seem to find a logical explanation yet !! but the it behaves has a pattern !!


    **EDIT: I just came back from a test, I replaced the DME with an old one .. still got the same problem, I disconnected the trigger sensor ( right plug next to the crank sensor ) and the engine behaved much better, not smooth but seems that the DME used the prediction method. but didn't run in 3cyl mode.

    do you think that was it? I reconnected it while engine was running but nothing changed. also gas smell was so obvious and few explosions happened in the exhaust afterwords.
    Bellevue WA
    90 535iM - not much stock remains. 3.7 liters, ported head, cammed, 3.73 diffy, M5 brakes, MAFed, yadda yadda yadda
    86 Porsche 951 - Track Toy

  9. #9
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    Jeff, in that case why would 2, 4 and 6 get affected, and why would if start normal then F-up when reving it? I removed the spark plugs and they look acceptable.

    Does the DME detect poor spark? or bad wires?

  10. #10
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    I went to the scrapyard today and got the sensor with the spark plug wire. but it didnt help up. I'm going !!

    today it was cold in the morning ... I started the engine and it idled just fine.

    when it warmed up I reved it and it got back to the problem ...

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