Thanks to all of you people here on this site, my car is back to running order and in much better shape than ever before... But I am still not out of the woods yet. For starters the car is an 84 4cyl 4 speed.

Here is the situation I am running into at the moment. The car when the throttle is quickly depressed either in gear and moving or out of gear in neutral will start to misfire at about 3-4k rpm. When the throttle is applied gradually it revs up ok but will eventually misfire at about 4-4.5k rpm.

The last time I drove it, I intentionally made it misfire for a little bit and then the rpms dropped out to 400 or so and wouldnt run unless I had the throttle fully open which would indicate a rich mixture. I am not sure as to what to look at next. Here is what I have noticed and checked.

I first thought the temp sensor to the ecm may be going, but the car starts in open loop and goes into closed loop and the ohm values seem to be appropriate from the charts I have found on here.

The ignition base timing has been set today to its appropriate timing.

The car idles at 1000 rpm when it is fully warmed up (may be a vac leak, need to look into that further still)

The car has a walbro 255 fuel pump in it currently which puts out a higher pressure fuel than the stock one does, and I am not sure if this may have an effect or not on the performance of the engine.

I inherited many problems with this car when I got it and I am getting SOOOO close to having it roadworthy. If anyone has any potential info on this please let me know. Thanks in advance for your help.

How old are the plug wires? Any wire cracks and / or how old is the coil. Wires fail with age and often crap out at higher rpm's.

------------------

Dont know of the wires age, but they look pretty new and they all have proper ohm readings for their length. Dont know of the coils age at all. I have a spare somewhere (dont know if its good or not)

I agree It is probably an ignition problem. Drive the car up a steep hill in a high gear so it really works the motor if it misses then it's definitly a ignition problem Check the cap and rotor ,plugs ( Make sure they are also properly gapped ),plug wires if ok change the ignition module. Good luck

------------------
Home of 3 1/2 Fieros, a 900HP AWD S10, a 1967 Pontiac Catalina Convertable, a Chevy Avalanche and lots of misc GM parts.

For the plug gap I know it is .060". I read somewhere that .055" is better? Should I do one or the other?

I was thinking the Walbro 255 was for a V6. If you are correct the fuel pressure is way to high. All you nee is about 12 lbs, and you have up around 50 lbs of fuel pressure. These are off of ther top of my head, and some one else can give you the correct pressures for the 84 2.5 as opposed to a 255 for a V6.

Yes, these are some of the issues i inherited when i got the car. The walbro is like 40-45psi and the stock pump is 15psi.

Could this be causing my issue?

Seems it would run rich and crappy through out the rpm range then.

I think I will try to get it on an oscilloscope and see if it is spark before I start playing part swapper.