I have a 94 z28 camaro and it runs real rich. Blows black smoke and before everything was done to it it would run ok when cold then when it got hot it would sputter real back and misfire and have no power at all and roll black smoke. Would want to take off but no power to push it. It would scream but the motor wand or car would go just not like it should. So we changed cap and rotor plugs and wires opti resealed EVERYTHING on motor and under car, PCV valve new intake boot and intake filter new coolant temp sensor new fuel pump about 2,500 dollars worth of parts and work. Now when started it tuns fine and idles fine even when warms up but when you drive it, it runs fine under 2000rpm and just at cruising speed but getting on it hard and above 2000rpm it just falls on its face and runs like crap kinda like before blows smoke and what not. So half of its fixed what do i do for the other half. lol we are changing the MAP sensor too here shortly. My guy said it seems like timing is off in it. Has a little backfire sometimes. Check Engine Light or SES was on too idk about still but it was being triggered. PLEASE PLEASE HELP ME!!!! There is also no wiring in the ECU plug in to read scan codes because some idiot before me had to have removed them.

 

Let's move this to "LT1 Based Engine Tech".

 

You need to reconnect the data link connector so you can scan it. There is only on key wire, and that's the tan one to pin M.

Have you checked the fuel pressure?

Did you change the O2 sensors?

Is the engine stock, or modified? If modified, what has been done to it?

Has the main body of the Opti been replaced? IF so, are you sure it was indexed correctly with the splined shaft?

 

Can't be too urgent a need for help... he never came back to the site to look since his (triplicate on 3 different forums) original post.