I have 94 Sierra it starts fine when cool and runs until it reaches operating temp then dies and won't start until it cools off.?

Question

I've had my ignition module checked at autozone it was fine and I cleaned the throttle body and idle air control valve still won't run when warmed up. also I replaced pump and filter a couple months ago and when it started running bad check engine light don't come on can anyone help point me in the right direction. thanks

Answer 1

The problem with testing ignition modules or coils is that they can work and test fine when cold but can fail when warmed up due to internal problems and higher resistance. I had a similar problem with a Grand Prix that ran fine when cold but died when the engine warmed up...was a bad module. Autozone ...or any other shop...would have to test the module when it's warmed up or heated to replicate the conditions when the truck dies and see if it's working properly at higher ambient temps or heat from the engine soaks into the module or coil.From your symptoms, it does sound like a failing module or coil when warmed up.



You might test for spark at the plugs when the engine is warmed up...idling in the driveway or shop...if no spark or weak spark during cranking when warmed up and after the engine dies, then it's likely an ignition issue...bad coil or module.



I'd start with that.

Answer 2

Does the check engine light work properly, or doesn't work at all? That is vital to know. If it's not working correctly, you need to start there.



You also need to do a very thorough underhood inspection, to include checking for vacuum leaks with an unlit propane torch, unless you find an obvious vacuum leak that once corrected, solves your issue.



Spent way too much time and money on things that have nothing to do with your problem (anyone with some time working on vehicles like this could tell you the same thing) so need to start on a logical path, which starts with inspection of components.



Obviously the problem is related to open vs. closed loop, which means that something isn't right when it goes closed loop, which is being hidden when in open loop due to the normally increased fueling.



Edit: Apparently R, who doesn't even have a full name (actually I believe the first iteration of this user was Raul) does not know proper diagnosis nor how vehicles actually work. Instead he would rather ramble on about how to properly use the English language (except paragraphs apparently) not how to actually fix your vehicle. Since GM hasn't used a heat shield on their fuel lines in forever, and have no need for one in a return-type fuel system, "R" 's guess, and entire post, is indeed of zero value. On his behalf, I apologize for his wasting your time.



And good thing too...R's post was removed quickly, as it should have been.

Answer 3

Unfortunately, this has OBDI it in.



Sorry, I don't have a clue. Good luck.