Jnelso

After running three 20 minute sessions at SCCA Track Night event at Palmer couple days ago, on my way home my 1999 C2 cut out. I pulled over to the side of the road sat for a couple of minutes and the car restarted. The engine cut out two more times but always restarted after a few minutes. I thought maybe it was the fuel pump relay, so I pulled into a parking lot to see if I could figure out what was going on. I lifted the rear shelf carpet where the ECU and a relay panel is located and noted that the ECU was extremely hot. I sat for a while and let it cool down and drove 94 miles home without any problem. Wondering if anyone else has had a similar experience. The air temperature at Palmer was in the low 80’s and I have tracked many times in hotter weather without any issues. Any thoughts that the extreme heat was generated by the ECU or residual heat from the drive train. Car has been running fine since and ran Durametric and found no fault codes.

Prelude Guy

First thing I would check are the positive and negative battery terminals. Also, make sure the ground wire is secure and clean at the chassis.

pdxmotorhead

bad coil or injector grounds or ECU ground will heat stuff up in a big way.. higher resistance often = more heat..

Jnelso

Good call on possible ground issues, I will be checking ground connections.. Thanks.

Prelude Guy

When you said the car wouldn't restart until it cooled down, did the car just crank and never fire up?

Honestly, another part I think you should consider replacing is the fuel pump preemptively. Since you track your car, I think it is actually more of a reason to replace it sooner than later. These pumps are old now. And I don't like randomly replacing parts if I don't have to.

I've been working on my 2004 BMW 330 ZHP. I am going to track it this year. I literally just changed the fuel pump last week. Its 15 years old. Even though it still worked, it can't be working optimally. It's never a good thing if an engine starves for fuel either.

Just a recommendation.

Jnelso

I know a 20 year old fuel pump is a liability, but I don’t believe that was the cause of my car cutting out. Need to figure out why the ECM got so hot.

Paul Waterloo

Do you have Durametric? Did you plug it in and check for any stored codes?

Jnelso

Yep, no codes.

pdxmotorhead

Something that's been a reoccurring theme,, on various cars I've owned, the ECU gets dodgy at 10 to 15 years,, usually because the capacitors have dried up,, just like good audio gear they need re-capped about every 10 years.. To work their best. if the ECU is not potted, remove the cover and check the caps, see if any are bulging, and if the ECU has heat spreaders on the power transistors, and they are bolted, I've had good luck taking the bolts out and cleaning between them and their contact point with electrical cleaner and some q-tips, then put some fresh thermal grease in and re-tighten,,
Havn't done this on a 911, but my 06 330XI did some weird stuff and after a couple hours on my bench getting new electrolytic's and some love to the power transistors it was fine. Potted ECU's are a way harder problem..