Pontiac Repair: hard starting-warm, chevron techron, fuel pressure regulator

Question
Hello there! This question is not about Pontiac but Chevrolet but i hope you can still help? i have a 1999 Cavalier Z24 with a 2.4L 5 speed. the problem is first thing in the morning car will start and run fine as soon as i start it and drive to approx. 90 degrees Celsius once i shut it off and let it sit for a bit it hesitates to start. once it catches it runs very rough but does not set a code. i am stumped. i have replaced ignition control module, both coils, boots, fuel filter and cleaned throttle body. it started this about a month ago but is progressively getting worse. any help would be appreciated.  Thanks.

Answer
Hi Chris:

well a few things to check here are all the engine gounds on the transmission studs. They have a tendency to ot out and corrode or just plain break off. Same with the connections at the battery and the gound on/under the battery tray. I would check for a leaking fuel pressure regulator. with the car running pull the vacuum hose off the regulator and let it run for a bit and see if raw fuel starts comming out of the regulator where the vacuum line goes on. I would Check the fuel pressure. Get it up to temp and then put a gauge on it and see what you have I belive that engine has about 42-47 PSI running.. You may want to try a product called top engine cleaner. Run a can or 2 through the engine and then let it sit over night and start it cold the next day. Also try a can of Chevron Techron fuel injector cleaner in the tank. Good luck :)