I have a all stock 94 Camaro Z28 with the 5.7 LT1. When you first start the car everything is fine, but after it has been running for a while it will start backfiring when you let up off the gas at highway speeds. When at idle you can hear it idling up and down and there will be no oil pressure. The car is also very hard to start once it has been running for a while, but if you let it sit for a day or so, it will fire right up when u hit the key. It is also burning fuel faster than I can put into the car and you can smell gas in the exhaust.

I have tried replacing the optispark. I have but new spark plugs and wires on the car and replaced the fuel filter and it is still do it. Does anyone have a clue to what may be causing my problem here?

 

sounds like o2 sensors to me... once the computer goes to closed loop it starts add or taking out a bunch of fuel.

 

Check your EGR valve. There was a recall on them years ago but the letter said no to bother having it replaced until it started acting up so a lot of folks didn't replace theirs. It could be the O2's or anything that depends on a sensor n closed loop.
Good Luck.

 

Is there any codes thrown? Have you hooked up a fuel pressure gauge? Have you tested the coil and the ICM? Lastly Ignition, fuel, etc will have nothing to do with oil pressure...if there is zero oil pressure, don't drive it!

 

It is not throwing any codes. It is showing some oil pressure, but it is not as high as it use to be. The engine also sounds like it is missing when it is at idle, but you can get it to run smoother if you press on the accelerator a little bit.

 

Check for codes, fuel pressure and maybe do a vacuum test. The O'2 like other things have been mentioned but its most likely your problem. I replaced my at 100,000 miles but i think 80,000 is recommended. Be sure to only buy AC Delco or your car may have more problems. Ebay has them real cheap compared to the dealer.

 

Ok i replaced both O2 sensors and the MAF today and it is still doing the same thing. But i can tell a difference in power though and the idling is a better. But now when when I hit the accelerator I can hear popping and feel the popping on my foot throught the gas petal. It does not do it all the time though.

 

might take a little while for the computer to relearn... you could cheat and just unhook the battery for a little while.