ok guys I probably did a stupid thing, I traded my 91 z28 convertible for a 91 z28 , the conv. has thousands of dollars in cosmetics that need to be done. traded for a 90,000 mile z28 that is beautiful, flawless interior, no dents, near perfect paint,etc. Both are TPI 305's, autos but really having a hard time diagnosing this problem.

I knew for a fact that the #5 injector was bad, so I replaced with a known good set. wow, car runs as it should, but after 30 mins of driving, when its hot, it misses,bogs, down and eventually dies, about 1-1.5 hrs later you can drive off again.

I'm going to start with basics:
coil
Temp sensor
TPS

also the fuel pump is brand new,ECM is new

Any suggestions as to what one should look for?

thanks in advance
James G

 

Sounds like the HEI module under the distributor cap is getting hot, causing a no spark issue while hot. I would check for spark when this happens. Just an idea for you to look at.

 

Thanks for the reply, I believe the module was recently replaced by previous owner-but def. a place to look, I drove the car 40 mins today with no issues. I'm replacing coil tomorrow and then, coolant sensor, and then the module.

thanks again
James G

 

It's possible when the module was replaced they didn't put enough heat sink gel under it.
worth checking out anyway.

 

POSITIVE the 2nd set of injectors are OK?

 

Check the fuel pressure. If it's running fine right now, check it and write down the current pressure, when it starts acting up again check the pressure again and compare to your notes.

 

Thanks again for the reply. Well injectors replaced, new MAP sensor, coil. car did run noticeably better. However, still at about 45 minutes, the car begins to sputter, until the throttle is no longer responsive. Going to try the ignition module soon.

But I think I may have found the problem. Once it stutters, then finally just dies. you can turn the ignition key on, and the fuel pump doesn't prime 2 out of 5 times. Car runs but then sputters out and dies within 5 mins.

Possible oil pressure sending unit? I do know the previous owner replaced the pump with OE unit from advance auto parts. I forget somewhere that had holley 255lph pumps on sale at one time. Any help there?

any help is greatly appreciated.
James G