We have a 99 jimmy with the 4.3L. With a no spark issue. It died on the way home from the doctors office. I recently did new plugs. So i decided sinceI had the stuff to illiminate the plug wires cap and rotor. The jimmy fired right up ran great. I wondering if it isnt the Ignition control module or coil heating up and then going out.. Is there a way to test them. Ive heard autozone does it. Is this true. Does anyone have any ideas. Am I on the right track?

 

I am not really much of a mechanic, but it sounds like you are on the right track. I'd try pulling one of your plug wires, put a screwdriver in it. have someone else crank it while you hold the screwdriver (carefully) about 1/2 an inch from the engine somewhere. If it is sparking properly, you will see it. It would be a good start at least. Like I said, I'm not much of a mechanic, I wish I could be more help.

 

I use a extra plug for that. Thats how I established a no spark issue.

 

I would be suspect of the coil first if it starts fine when the engine is cool.

 

After alot of chasing and replacing burnt out sensors I figured it out. The wiring harness was shorting out causeing sensors to burn up.

 

Where was the harness shorting out?
It might help someone out in the future to know.