Now what?

[Parentnoia]

Well as some of y'all may or may not know, my (now ex) girlfriend managed to overheat my suburban and both heads wound up cracked and being replaced. Well after a few months of being apart and turning into a lawn ornament, my suburban is back into running condition. Problem is that it's far from road worthy. Idles high, runs rich, uncle says he can hear it missing and has a vacuum leak, and his scanner says that it's not going into closed loop and is recording 0 misfires. It also doesnt start while the engine is hot. It has to be completely cool before it will start. Everything is plugged in and in the same condition it was in pre-overheat. Granted, it didnt run perfect to begin with, it definitely wasnt this bad.

 

[jrollings]

Not starting when hot tells me the ignition control module is bad or going bad. Hopefully others will chime in soon.

 

[90W7]

Agreed on the ignition module. Mine would die as it got hot and I would have a crank no start until it cooled enough. Installed a new module and the problem was solved.

I would replace that first and fix the vacuum leak. That will alleviate the majority of your problems.

 

[Parentnoia]

Where's the ignition module?

Edit: Google is my friend. But how would that have died in the process of overheating, or could it have been bad timing?

 

[90W7]

could just be coincidence.

 

[90W7]

Not to shotgun parts at it but you might want to put a new coolant temp sensor in it aswell just cause it's cheap and a known source of problems.

If the sensors is bad and telling the ecm its always cold it will continue to run rich in open loop. Garbage in garbage out.

 

[Parentnoia]

Well folks, I changed out the ICM, and it's back on the road, for the most part. It idles rough, but doesnt try to die like it did. Sounds like there's a bad vacuum leak. And the idle fluctuates badly when at a full stop on the brakes, so I think the vacuum leak is related to the brake booster hose. I'm satisfied enough with today's spoils to call it a day until tomorrow. Any suggestions what to look at first when I get back into it?