Engine bucking at high RPM

[KITT's1989Glory]

I'm having a problem w/ my '89 tpi trans am, it wont let me rev up to 5,000 rpm. when i get to like 3,500 or 4,000 the car starts to buck n sound like im hittin the rev limiter. i changed plugs, wires, and o2, got a new intake and cleaned my throttle body. the block learn and the fuel integration systems say its running fine tho...so im stumped

[maroman88]

in drive or neutral?

[KITT's1989Glory]

i have a complete loss of power all around...i have a 5spd n like it will not let me stretch my gears at all

[Formulalt1]

Check the fuel pressure under WOT. My old pump gave fine pressure at idle and under partial throttle but once you put the demand of WOT or high rpms on it, it would pull back and buck. Might be ignition related but sounds like fuel delivery to me.

Edit- Oh wait you have a TPI, those feel like a brick wall at 5K unless you made mods to make her breath up top. I owned two TPI's and both did not like the 4800 + area of the rpms.

[GP99GT]

like he said, check fuel pressure at WOT if you can, the pump may be failing...fuel cut at high RPM would cause those symptoms

[KITT's1989Glory]

Im new to this forum n just wanted to say thats for the quick response. the car has a new pump tho...when he was running good he would rev up to 5,000 rpm easy the car does have a hypertech chip in it, 3in exhaust, air intake, and better flow plenum (i think thats wat its called)..........my fuel lines are metal up until a little b4 the tank where i put steel braided lines to the fuel tank tho idk if that would have anything to do w/ it. the fuel filter is new too.

the car is also misfiring

[Formulalt1]

Ok, then most likely you have a ignition related problem but its still doesn't hurt to check your fuel pressure across the board. Alot of times its difficult to diagnose based simply on the symptoms as fuel delivery issues and ignition issues can cause the same problems. A weak coil, a bad ignition module, fouled plugs, cracked or fouled wires and so on and so on can all cause you to miss and cause high rpm issues as a stronger spark is necessary up top and under heavy loads on the engine. I would just rule out pressure first then check the status of the spark and then you get to move on to trying to diagnose the injectors. Good luck,

[KITT's1989Glory]

thanks alot i really appreciate it ima start checkin that out...i also checked my maf sensor n im gonna try n check other sensors cuz i also thought that mayb the ecm is getting a false reading from a sensor thats causin the car to go wacko. well im start checkin ill let u kno wat i find.

[DaSkinnyGuy]

sounds to me like theres a fouled spark plug

[KITT's1989Glory]

But I changed the spark plugs I'm gonna do a compression test n c wat comes up. Hopefully ill find the problem there

[KITT's1989Glory]

my compression came out good n i changed my distributor cap n rotor

[Tru2Chevy]

Originally Posted by Formulalt1

Check the fuel pressure under WOT. My old pump gave fine pressure at idle and under partial throttle but once you put the demand of WOT or high rpms on it, it would pull back and buck. Might be ignition related but sounds like fuel delivery to me.

Originally Posted by GP99GT

like he said, check fuel pressure at WOT if you can, the pump may be failing...fuel cut at high RPM would cause those symptoms

Check your fuel pressure at WOT with the car under load (as in actually driving - not parked in your driveway).

- Justin

[KITT's1989Glory]

well guys i think i got it figured out...i checked the resistance for the injectors and low and behold they were all way outta range...they were supposed to register 15.5-16.5 ohms n they were all way under that. i could have fried the injectors way back when i had a short to ground. so now i just have to double check the computer n the injectors b/c 1 of them is the problem (also had moisture in my fuel) thanks for all ur help i couldnt have got this far w/o u guys