My blazer runs seemingly fine unless it is hot outside. It will stall completely then start right back up. The longer I let it cool after stalling the longer I am able to drive afterwards. I have changed the ignition control module, fuel pump, spark plugs and wires, fuel filter and thermostat. It is nearly impossible for a pro to diagnose since the problem only occurs in warm weather after driving for close to 2 hours.

 

Questions: when it stalls and then starts right back up....how long will it run before stalling again?

Have you check all the electrical connections; ECM connectors, grounds clean, alternator wires, etc.....to ensure all tight and making good electrical connections??

Next item that comes to mind would be the ignition coil, however, it usually takes a cool-down period for the coil to begin working again when it fails at hot.

Could also be an intermittent fault in the ECM, but this is not very common.

 

When it stalls, it may be started immediately after but will stall shortly thereafter. The longer it is allowed to cool down is directly related to how long it will run afterwards. I have visually inspected nearly every connector and have yet to find anything suspect. A friend of mine suggested checking the ERG but I can't seem to locate it. All of the diagrams I've looked at show it to be in a place that it isn't on my year model. I'm assuming the ECM doesn't throw a CEL?

 

Check the spark the next time it does it.
2004? Does not have an EGR.

 

I did the following on a 95 Corvette to determine the ECM had a hot failure;
used a wet towel/rag and placed on top of the ECM after the engine stalled and found that as long as I kept the ECM cool the engine would not stall.

Not saying that the ECM is failing in yours, but something to try to eliminate it.

There use to be a freeze spray available for electronics that would work inplace of wet towels, but I could never find it. This could also be used to spray the ignition coil to see if keeping it cool would prevent the stalling. Do not recommend trying to use a wet towel on the coil.

Good luck with this.

 

Or you can aim a blow dryer at the ICM to see if it stalls when hot.

 

Or you have yet another ignition switch problem. The connecting "fins" get hot and loose contact. Its a way out idea but to me anything is possible.