1989 Firebird, 305 tpi. Has a miss and cant find the cause. New plugs,wires,cap,rotor,coil,egr,vacum lines,tps,fuel pump, fuel injectors, fuel filter,oxygen sensor and ignition module. I did have a code come up, it said rich exhaust. There is no more check engine light on, but I cant scan the computer for codes any more. The car will stay running as long as the gas pedal is slightly depressed, other wise it stalls and is very hard to start unless gas pedal is depressed all the way. Any ideas would be great.

 

Sounds like the TPS might not be in proper adjustment... do you know how to set it up? Also, what is your igntion timing set to?

 

do you have any problems with your engine "surging" when you bring the car to a stop, say at a traffic light or stop sign?

 

Yes the throttle position sensor was set up correctly by both me and my local mechanic. The car does not surge at all when coming to a stop, the car just stumbles then dies.

 

im not to sure but do tuned ports use an IAC?

that could be a problem

 

How hard do you drive the car?? I had a similar problem on a carb motor, took a similar approach to fixing it, then someone suggested I didn't drive it hard enough. I got to thinking, the car was only driven about 10 or so miles a day, and not very hard. I found some back roads, drive the **** out of for 30 or 45 minutes and it cleard the miss. I figured it was carbon buildup on the valves and driving it hard cleared it off some. Also try a small bottle of injector and valve cleaner.

 

that fixes everything lol i like it!!!!

 

Same problem I'm having now with a 91 z28 and 305 TPI. So far we've replaced the distributer and IAC. After the IAC it stopped dieing, but it still misses at all rev ranges. The weird thing is that it doesn't alway do this. If you drive it real light, you can rip through first and second gears pretty fast, but then the engine starts to miss extremely badly and theres no power. Yesterday I couldn't get the car over 25. Mechanics looking at it now, if he finds the problem I'll let you know.

 

Alright we found out what the problem was today. The ECU was bad, making the injectors not open at all. Your problem sounds almost exactly like what I had, so maybe its the same cause.

 

Connect a vacuum gauge and check the manifold vacuum at the lowest stable idle you can get. Tell us what the reading is. If the needle is a blur you may have a leaking intake valve or broken valve spring.