I just bought a 93 z28 and it drove and ran fine when I test drove it. Drove it almost 2 hours home and everything was fine until i was 4 miles from my house. When accelerating out of town it sputtered 4 or 5 times then it was fine. 2 miles later i set the cruise at 65 mph heard some clinking under my feet and my car started to bog down. Every time I pushed the gas the car wanted to die. It shook real bad and ran like crap. Turned it off and tried to start it. It cranked and cranked but nothing. Couple minutes later it cranked and started but ran low rpm's and died. I finally was able to drive it back at about 35 mph in the same condition pulled in my driveway and it died. 5 minutes later tried to start it crank crank crank crank nothing! Later that night it started just fine and drove normal. Today it seems fine also. It has magnaflow exhaust, with stock manifolds. Car has 111,500 miles and it sat for about 2 years. Sorry for the long story but I hit a deer and totaled my other car now I have no vehicle until my camaro is fixed!

 

I would scan it for codes. I also would check fuel pressure. The noise at your feet and some of your symptoms might have me question your catalytic converter.


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Mechanic plugged it in and said everything looked fine 02 sensors were working fine. Only code I got was to do with EGR valve. Maybe it stuck and caused that. If there was a problem with the cat converters would that have thrown a code?

 

Bad check valve??

 

I would check fuel pressure first. Your pump might be going out which would explain why sometimes it works fine and other times it won't even start. Fuel pumps can act like that when they're dying. Maybe the noises were from the vibrations from the stumbling motor?

 

Do you realize that on a 93 LT1 (that year only) you can flash the codes on the SES light?

Courtesy of Shoebox:

http://shbox.com/1/dlc2.jpg

http://shbox.com/1/Dtcs.htm

Which EGR codes did you get? There is one for the electrical circuit to the EGR vacuum solenoid, and another code for low EGR flow. You need to post the exact numbers, not just the descriptions.

There are no codes in OBD-I that are related to the cat converter performance.

Look at things that can heat soak - the ignition control module (ICM), the optical cam position sensor in the Optispark distributor and the fuel pump are a few tings that come to mind.