Hot ECM?

[Chris Kennedy]

Hi! Ever since I've had my '81 4-spd. (about 82K miles of the 180K) the ECM in the compartment behind the driver seat has gotten really hot after an extended drive. By now I have stopped worrying about it, but have wondered whether others have noticed the same thing. Is it normal? I may start raising the lid on the compartment to try and circulate some air into it. I keep a spare ECM in the car, but was wondering what happens if the ECM dies---I read the manuals as saying the car goes into a "limp" mode....has anyone experienced this?

--Chris Kennedy

 

[Vader]

On an E4ME, Backup Fuel and Spark Mode ("Limp home mode") isn't going to make a great deal of difference. Even less with a manual, since you don't have a TCC to lose. You'll go a little rich, and get a little less total advance, but that's about it.

As for the original question, what are you calling "hot"? Too hot to touch, ot just too hot to lay any "more sensitive" body parts on comfortably? If it's hot enough that you cannot place your hand on it, you have a problem. Otherwise, it's fairly normal to generate some heating. If it's too hot, you may have a load problem with the EGR solenoid, EVAP purge solenoid, or an MC that is shorting (but you should get a '23' from that). I'm presuming you're not getting error codes, right?

The EVAP and EGR are my first suspects since the duty-cycles of those is greatest at part-throttle cruise, as you are describing.