Hey guys, my 93 Z28 runs great as it should when its cold but when it gets warm it starts back firing and it dies and when you try to refire it it acts like its out of time and it will barely let it crank. Its ok most of the time if you just let it idle but if you put a load against it it will start backfiring and missing and want to die. Its got 129K miles on it, its got 29K on a GMPP optispark. I dont want to just go replacing parts. So any an all help would be greatly appreciated. Its mostly stock. it has a polished vortech intake with a MSD blaster coil. I think thats all thats done to it off the top of my head. Thanks in advance.

Nick

 

try checking for codes...you gotta have a starting point...

 

My '94 did the same thing. It was a bad O2 sensor.

It ran fine when cold, then as soon as it went into closed loop, it ran terrible.

Replacing the sensor cleared it right up.

 

I will get some codes pulled when the rain stops. The car dont come out in the rain. Thanx Jon, the O2 sensors are fairly new, but they are made by bosch so that dont mean anything lol. Thanks to you both.

 

Have you been noticing a different sound to your fuel pump when turning the key to prime?

 

I just had this same problem i replaced my bosch o2 with a/c delco and the car runs great again

 

Mine did that and it ended up being the icm. Does it run good again after the car cools down for a while, or is it an open loop, closed loop issue? You should check whatever codes it throws.

 

Sounds like the issue I had with my car when the headers were open. On the first ride it was sweet... For about 10 min. Then it was a nightmare when it went into closed loop. With the new "y" pipe it is like having a new car.