I just bought a 1994 Z-28, it's been misfiring really bad. So i brought it in to get a diagnostic. I had 5 codes -EGR, O2 sensors, Air pump Circuit, and 2 exhaust leaks. I fixed all of those and it still misfired. So then i replaced plugs, wires, cap and rotor, and just last week i replaced the WHOLE distributor. (STILL MISFIRES) I have no idea what to do...I'm about to give up on the car. Someone please give me some helpfull information.

 

check your injectors and fuel pump

 

As above, check fuel pump and pressure regulator, use a FI pressure gauge, guessing won't do it. Change fuel filter, Also get a set of NOID lites & verify that all injectors are being fired. If still NG clean & test injectors. Also using a scanner (not a code reader), check the output data of all sensors & verify that it makes sense. You may have a lying sensor.

 

I forgot to mension some of that stuff actually. The first thing that i did was replace the fuel pressure regulator. I had the injectors cleaned and I had my fuel pump checked,(they said it was starting to get weak but that it shouldn't be the problem) Now my SES light is still on, it comes on about 2-3 min after i start it. They told me it was still reading codes from my o2 sensors and my EGR valve.

 

May want to check the cat out. If it is clogged it will cause the O2 sensors to go bad and the EGR to act weird. If it hasn't been done, check the firing of the injectors with NOID lites to make sure there are no wiring problems.

 

I don't have a catalitic converter. I took it out and have a full exhaust with hooker headers to 3' all the way back to a muffler. How much would one of those Noid lite checks be?? (average price)

 

They are cheap, $20-$40. Some Autozone stores have them.
http://www.etoolcart.com/browseprodu...-OTC3050C.html
http://tools.batauto.com/index.php?c...on=show_detail

 

I had the same problem with my 94 Z, i replaced the distributer and the plugs and it solved the problem, but from it misfiring soo bad it cause the fuel pump to go, check your fuel pump regulator.. and if that doesn't work and you want to keep the car, look for another engine...trust me you can find one in your price range if you had the money to replace all that. good luck.

 

Sure it's a fire problem? Check EGR operation. Too much exhaust back into mix will cause it to run like crap. Do away with it if it's legal in your state.