if ecu touches metal, car runs on 2 cylinders

[Lof8]

I've been struggling with a very annoying ignition problem for about 2 months. My car will intermittently run on only 2 cylinders. Sometimes it runs perfectly and others it limps around with no spark and no fuel going to cylinders 2 & 3. I thought I had found the problem when I found a loose ground wire connection on my battery terminal and the car ran great for 2 days- but it came back.

I have replaced the plugs, wires, coil, and CAS with no major results. I took out the ecu to look for loose connections etc. and found that the car runs perfect with the ecu sitting on the passenger side floor but as soon as it touches the metal brackets, where it bolts in place, the 2 cyl crap starts.

I can sit there with the ecu in my hand and touch it to the metal- immediately runs like crap. Pull it away, and it runs great again. This is a really weird problem. There are no visible problems in the ecu.

Has anyone had any similar problems or have any ideas for me?
thanks, Andy

 

[skelly]

Interesting problem. where does the ECU mount on these cars? (Yes, I'm new) In my Ford Probe the ECU is mounted on the floor of the center console right below the stereo deck. If I had to guess a cause it would be that perhaps something nearby is shorting and supplying voltage to the brackets near where the ECU mounts. In that case, rather than seeing a grounded chassis, the ECU would see positive voltage there. One way that you might try to test this theory is to run a temporary, dedicated ground wire directly from your negative battery terminal to the chassis of the ECU. If everything runs normally, then a short probably exists near where the ECU mounts; if however the problem returns, then there may be a problem internal to the ECU.

HTH
- SK

 

[IWANTSPEED90DSM]

WTF, is your ECU just dangling there or something? why would it just randomly start touching metal?

 

[steve]

Sounds like one of the EMI caps on either the injectors or the power transistor is shorted.
I haven't seen any ECUs yet with that problem but Dave Mertz of DSMlink has reported the problem. They are a pain to get at and replace.

Steve

 

[Lof8]

WTF, is your ECU just dangling there or something? why would it just randomly start touching metal?

No, the ecu was bolted in place- making the problem even weirder. Why was it intermittent??? It runs fine with the ecu on the floor but as soon as it touches the bracket- craps out.

what does EMI mean?
thanks guys