I am a new and very proud owner of a 1994 Z28 and I am very clueless as to these engines so far. And I have never been knowledgeable with electronics! my problem is that when it reaches 160f or higher and I try to get on it it will hesitate. It's not like a miss and it won't stall on me is like it just stops putting sufficient fuel to the motor. Like you just took your foot of the gas. The previous owner says it got all new plugs and wires. When it's cold it runs awesome! But once it gets slightly hot and you put the throttle down quickly either from a dead stop or a roll on it will just stop getting fuel. Put in neutral and it will rev just fine.last owner says something with the PCM but I'm clueless. I don't want to spend a fortune trying to figure this out so please someone help!!! I have wanted one of these beautiful cars for so long and worked my tail off to get it and I'm so proud! Please guys help me out!!!

 

Try checking fuel pressure,Ignition control moduel,coil,or everyones favorite the Opti spark..

 

I had the same problem when I first bought my camaro and it was the opti.

 

Have a scan done on the computer. Even without the check engine light on, you can get data that will help diagnose the problem instead of getting a thousand guesses. THere are several software programs available that can help you get the data out of the PCM.

Since the problem seems to be engine temperature related. look there first with the scan. If, for example, the PCM thinks the coolant is cooler than it really is, then it will fuel it much more richly than you need...leading to driveability issues. In that case, the problem would likely be the coolant temperature sensor in the water pump housing.

Good Luck.....

 

New opti,plugs,wires,ignition coil,tried another module,same problem,new water pump sensor...fixed hard start issues,problem still there....bad ground from pcm or bad pcm?..see lt1 hesitating when hot in this forum mike.

 

Force it to stay in open loop operation by unplugging an O2 and see if it runs better.

 

pulling the oxygen sensors seems like the easiest try but i can not ger to the one on the left side(looking at the motor) either from the bottom or the top! it seems impossible! i want to try the closed loop thing but what the heck?! how do i get to the one o2?

 

Doesn't matter which one you do. For me the driver side was easier. Got to it from the top.

 

Ive had my 94 Z28 for exactly a week, and today I drove it the farthest Ive drove it since Ive had it. I stopped and got gas, and mine started doing the same thing. I thought it was bad gas, but I also noticed it was running a little warmer than usual...so i went and bought antifreeze to put in cause I think my radiator has a small leak. Im hoping that mine is just from running warm, but if not then I'll try unplugging my O2 sensor and see if that might be the problem.

 

I went to the auto parts store today to try to get the OBD1 read, but they didn't have the machine to do it. He gave me the key to use and the check engine light just continued to flash, I couldn't get a code out of it, any clues on that?
Also, the guy told me that I have to disconnect both O2 sensors, not just one or it will not run on a complete closed loop.
I can not even get my hand through the top of the motor to even touch the sensor, the other I can get to from the bottom easily.
I could just use a regular wrench to unscrew the O2 sensor????? I appreciate all your help.

 

You can't flash the codes on a 94....that ended with the 93's.

I don't know why you're having so much trouble with the sensors.... Just follow the wire and unplug it.....the connector is about 8" away from the sensor. There is plenty of room.....

Don't remove the sensor from the manifold.....you need to have the hole blocked.....

 

No you don't have to unplug both of them. The store clerk is Mo. No you don't remove them. Simply unplug one. Then the PCM goes into OPEN loop. Then if it runs better than it did before, you know the problem is from poor closed loop control.

Auto parts stores have not been able to read OBDI in a long time. You should see them when a 95 F body comes in. They go crazy.