So ever since i bought my 1994 z28 camaro ive had a real bad backfire at around 1000-3000 rpms and almost no power at all, very hard to take off from a stop, after 3000 rpms it has a little more power and doesnt backfire as much but below 3500, its horrible... idles kinda rough and usualy takes a couple trys to start. Has brand new plugs, wires, coil. Im wondering if it could be the optispark or a sensor? maybe injectors or something? When i recently change my cylinder heads only 6 were firing, so that is obviously a huge part of it just cant figure out what it is please help, thanks.

 

Have you scanned it for codes? Have you checked the fuel pressure? How old are the O2 sensors?

 

no i didnt get it scanned because the ses light wasnt on, not sure how old the O2 sensors are but may it have to do with one of the sensors comming out of my wireing harness has 4 pins and 2 of them got melted off and 2 are sitll there but it plugs into the passenger side O2 sensor off my header fine its just missing 2 pins. and i didnt check anything fuel related im leaning more towards spark but i could be wrong.

 

There are codes that don't turn the SES light on, including two for the Opti that might be part of the problem.

If your passenger side O2 harness connector is missing two pins (or wires for two pins) you would have a code. You need the two wires for the heater circuit and the two wires for the sensing element for the sensor to work correctly, and if either circuit is incomplete, you get a code.

Are you sure your SES light is even working? Does it come on for a couple seconds when you turn the key to "on".

 

yeah its working i see it when i turn key.. but then it goes off, im thinking its my distributor but i really want to figure this out without spending a ton of cash.

 

Sounds like timing, but you said you replaced the heads. While out jeeping in the snow, with my old 350 chevy landcruiser, I had a rocker arm loosen up and slip the push rod on the number 5 cylinder. No power, and back firing out the carb like it was 180 degree off. Oh it ran enough like a brigg and straton. Go back and check everything, Kevin.

 

checked the timing today, looks fine, put everything back and now its running even worse... i really need some advice

 

How did you check timing - pull Opti and verify it is indexed correctly to the cam?

The easiest way to solve the problem without spending a ton of cash is to try and pull the codes. If you can't find a used OBD-I scanner cheap, get the free software, buy a cable and scan it with a laptop.

You haven't really addressed the fact that you have bad O2 sensor wiring. You've blown off the idea it could be fuel related.

Not much more I can do to help.