Hi all! I have spent a huge amount of time on this site, but this is my first post. I have a 89 firebird with a 2.8 and 5 speed manual tranny. To make a very long story short, it sat for 5 years not driven. I recently put fresh paint on it and upon starting to drive it daily, I'm having a big problem that I just can't figure out. It starts up fine, although it idles just a little rough for the first 30 seconds or so. Once I start accelerating, it runs ok under about 20 percent throttle, but anything beyond that makes it miss worse the further you push the throttle (with no increase in acceleration at all). If I push the clutch in and rev it up, it revs up nice and smooth throughout the entire RPM band. I have done resistance checks on the ignition coil, and the pickup coil, I have replaced the distributor cap and rotor, had the ignition module tested multiple times, replaced all the spark plugs and gapped them at .045, the wires were replaced almost right before it sat and their resistances are all good, checked the fuel pressure (which is fine), checked the resistance on all the injectors and they are fine, the gas is new, the timing is at 10* when idling. I'm sure I've done more that I can't think of at the moment. I am thinking it's ignition related as there is unburned fuel at the exhaust tip. Has anyone else had a problem like this only under accelerating? I've found similar issues on other forums, but their resolution didn't match my situation. Is there a component that can test good put still be bad and produce a weak enough spark to cause problems under load? I'm going crazy here. Any help would be extremely appreciated. And I apologize if the answer to my specific circumstance is somewhere that I just couldn't find.

 

I would suspect that your injectors are either sticking or need to be cleaned. The original injectors in these engines are a known trouble spot, and I've had them go bad in engines that sat for a long time without running.

 

ignition control moudle can test good but be bad , but i dont think thats ur issue, as they normally act up once they warm up , not when u first start the car.

im sure u covered the basics and checked for vacum leaks and burnt plug wires.

have u tried testing the egr valve sometimes they stick open and will cause some of the issues u are experiancing

 

Rough idle could be the MAF sensor or a coolant temp sensor issue.

If the tach jumps while the engine is misfiring while attempting to accelerate, the ignition module is just about dead.

However, if you're not getting a full burn of the fuel, and since you've checked or replaced everything else, the coil is suspect (I know, you already checked it, but I've never had a resistance test mean anything for a coil). Pull the coil wire off of the dizzy and put a plug in it to check the spark quality.