Hello there and welcome to the BMW Car Club of America.

If you are a BMW CCA member, please log in and introduce yourself in our Member Introductions section.

e36 M3 mysterious miss

Discussion in 'E36 M3 (1995-1999)' started by dki97m34, Feb 20, 2009.

    dki97m34 guest

    Post Count: 5
    Likes Received:0
    Once a sporadic problem, the miss I am experiencing is getting more frequent.

    It is always the #2 cylinder.

    It is usually triggered by sitting at idle for more than a minute or two.

    It frequently happens just after coming off the highway and then sitting at a stoplight idling.

    It invariably goes away if I just turn the ignition off for a few seconds and then start the engine back up.

    I have switched plugs, coil packs and plug-to-coil-pack connectors, all to no avail. The miss remains in #2.

    I have run copious amounts of injector cleaner through the gas tank.

    I have had the fuel rail pulled and the injectors inspected.

    What is left? The wires that pass for what used to be the plug wires?

    Help!!!
    • Member
    • Technical Service Advisor

    mooseheadm5

    Post Count: 1,880
    Likes Received:15
    Could be the ECU, but hard to say. I am guessing it gives you a code? You did not say what year it is.

    dki97m34 guest

    Post Count: 5
    Likes Received:0
    1997 M3 sedan. The fault code invariably indicates a miss in the no. 2 cylinder.
    • Member
    • Technical Service Advisor

    mooseheadm5

    Post Count: 1,880
    Likes Received:15
    I think it will require further diagnostics, unfortunately. This will not likely be a simple problem and the only way to do a swap test is to find a shop with an Autologic or GT1 and a spare ECU. The reason I suspect the ECU is that the key off reset of the problem sounds suspiciously like an electronic component overheat.

    dki97m34 guest

    Post Count: 5
    Likes Received:0
    You were right. It was the cpu. Expensive, but what price peace of mind? Besides, to put it in perspective, it amounted to only a couple of car payments.
    • Member
    • Technical Service Advisor

    mooseheadm5

    Post Count: 1,880
    Likes Received:15
    Can I have your old ECU? I need one to gut the plug off so I can run Megasquirt.

    dki97m34 guest

    Post Count: 5
    Likes Received:0
    Shop kept the old one for core charge.
    • Member
    • Technical Service Advisor

    mooseheadm5

    Post Count: 1,880
    Likes Received:15
    Core charge? Really? I wonder if they have the same idea that I do. These things are not exactly rebuildable.

    dki97m34 guest

    Post Count: 5
    Likes Received:0
    Turns out the ecu replacement didn't fix it. Ran new ground wire from #2 injector to cpu and that seemed to make less frequent, but still throws a code occasionally and misses. Sometimes miss goes away after driving a mile or two. Always goes away if shut off and restart.


    Found the problem. Decided to have engine rebuilt (has 180K+ on it). When the head was removed, it looked like a previous owner had done the money shift. One of the valves in the #2 cylinder was bent and the valve seat was shot. I have put 70K miles on the car since I bought it, have tracked it several times and would have never guessed the engine was in the shape it was in. Someone obviously did the most minimal repair possible after floating the valves into the pistons and slapped it back together.

    Oh well, this is a good excuse for having Tim McCracken at KC Autosport put some racing pistons in, install a Sachs clutch and lightweight flywheel, etc. and farm out the head to Paul Burke for some of his mojo. Should be fun to drive when I get it back.

Share This Page