1993 Jeep Grand Cherokee • 200,000 miles

I have a 1993 Grand Cherokee 5.2 v8 4x4. When the temperature gets above 85F outside, it will usually start straight away. When I run errands I find that after I make about two stops, the vehicle refuses to start. Sometimes it starts, idles roughly for a few seconds, then shuts off. After that it will not start until I let it cool for an hour or two.

If the temp is above 95F outside, it simply refuses to start. Battery is fine, engine turns over, but it wont idle. In temps below 75F, it runs perfectly. Drove it from Oct-April with no problems at all. Being late May, with temps rising, this is occuring daily. It is fine in the cool morning and evening temps, but midday I simply can't rely on it.

I have taken it to my very reliable mechanic, but he seems to find no problems with it. PCM shows all is well. I'm at a loss.
May 27, 2012.

It may be that the throttle body needs to be clean. When the engine starts it runs it a little rich to get it going. If the throttle body entrance is dirty it might not get enough air and be so rich that it wants to stall when its hot out.
I am also giving you a walk through diagnostic for your situation just to cover any other possibilities. Just us the link below.

Yesterday I cleaned the throttle body. It wasn't excessively dirty, just very minor build-up. I went through the entire diagnostic on this site, everything came out working properly.

I also went throught the entire manual, trying step by step to see what might be wrong in both the fuel and electrical systems. Everything came out proper. Yet, I am still having the same problem. The only thing that I haven't tried is replacing the fuel filter. Do you think that could cause my problem? I'm reluctant to just start replacing hoses/fuel lines when the diagnostic tests indicated that the systems are working properly.

May 28, 2012.
It coudl be the injector pulse box. Check the wiring for cororsion.