breaking up around 4500

[CompOrangeSN95]

My car (1994 GT EFI 5.0) is breaking up around 4,500 rpm but only after it warms up. I can't figure out what is wrong with it, I originally thought it was timing, but i have it set to about 13deg advanced which should be fine. Any Ideas on what to play with to try and get it running clean?

 

[9psi 98]

Is it breaking up at any time over 4500rpm's or just at wide open throttle?

 

[CompOrangeSN95]

I can't get it past 4,500 once it warms up. I know its bad for the motor, but when it's cold it will rev to 6,000... it almost sounds like its not getting enof air/fuel to keep going, but that doesn't make sense to me because why would it work fine on start up and develop a problem after it is warm?

 

[9psi 98]

When it's cold it's operating in an open loop, which makes it run richer than usual to try to warm itself up. Your car is having trouble with the closed loop. Sounds like a timing. The first thing that I would do is disconnect the negative terminal of the battery for about 10 minutes. That will clear out the computer's memory. Connect it again and let it run. The ECU will recalibrate itself. Let us know if that solves the problem.

 

[CompOrangeSN95]

ok cool, thanks for the tip, I'll give it a try when i get home and let you know if it fixes the problem.

 

[birel21y]

It can be a ton of things. For me in my similar situation, it was the CCRM one time, and the alternator shorting out another time. all after the car warmed up. Can be the distributor as well. If you have any spares, start swapping. Check all your spark plug boots. a cracked one can cause a misfire. It seems like a ignition problem.

 

[CompOrangeSN95]

Yeah, it is definitely a gremlin somewhere, I guess i just start digging through it till I can fix the problem haha

 

[9psi 98]

Reset the computer FIRST. it'll eliminate a bunch of BS and help us diagnose it quicker.

 

[CompOrangeSN95]

Reset the computer FIRST. it'll eliminate a bunch of BS and help us diagnose it quicker.

That will be the first thing i do, it's the easiest possible fix, and if it doesnt work then its on to the other things untill i can figure it out

 

[2002BLGT]

check engine light on ? have you pulled the codes from it ? sounds like PIP sensor , or TFI module if its heat related , the PIP sensor fails more times on the 94-95 cars than the TFI on these cars

 

[F1atlander]

i still thinking timing. you pulled the spout connector when you checked the timing right? (just askin) and make sure the balancer hasnt spun? ive had that problem alot on my foxes.

 

[CompOrangeSN95]

I've decided to leave it for now, im going to finish with my roll cage and get my new exhaust in before I tackle this problem, I don't feel like chasing gremlins right now. thanks for all the help though.

 

[sn95gtvert]

sounds just like when my maf sensor was dirty. cold it ran alirght warm it broke up like mad and hated everything. clean your mass airflow sensor it only takes about 15 minutes start to finish, and will really wake the car up if this is your gremlin.

i would do this before messing with timing. also try putting the base back down to 10 so you know for sure its not going to ping or damage anything while its running rough.