I have a 1994 z28 and the check engine light is on and i plugged it in to a Snap-On diognostic computer and it doesnt read any codes. When i step on the gas it bogs the engine down and it will die but if i give it a little bit of gas at a time it will rap out and after i rev it up a little it will run fine for a while. Other times its running fine then i'll like pull up to a stop light and it will idle at about 500 rpm then when i go to take off it just dies and wont start back up unless i let it sit for like 15 mins or push start it, But if i take it out and just rod the crap out of it the check engine light will turn off and it will be fine untill i let it sit for like an hour then its right back on so i dont know whats wrong i'm thinking it could be a sensor or something?

 

If you could get the code, man it would really help. Anyways, does it act like this after the engine has warmed up or when it's cold also? How long has it been since a tune up? If it does it only/mostly when the engine is warm, chances are it's a sensor since the PCM is in closed loop and taking measurements from the sensors. Is that Snap-On computer capable of reading sensor outputs while the engine is running (should be)? If so, you can get us some sensor output data and post it.

Not enough info to accurately tell ya what's wrong. At a guess, either the O2 sensor or throttle position sensor (TPS). If bad, both will make your car run like described. O2 sensor output should bounce between 100mV-900mV. With the engine off and key in run position the output from the TPS should be 0.60V at no throttle an go to about 4.5V at full throttle with places where the output drops out.

 

Try another scanner and see if it can get the code(s).

 

are you sure its an OBD1 scanner? you may have used an OBDII scanner. Try going to a mechanic shop to have them scan it just buy him lunch and call it even.