Thread: Acceleration Problem past 3500rpms

I’ve looked all through this forum and haven’t found a similar problem to the one I’m having.

My car is a 2002 GP GT, mods include 3" downpipe, resonator, no mufflers, and a 9" open cone air filter.

At in town speeds 0-40mph the vehicle behaves normal accelerating through the gears with equal appropriate acceleration. Accelerating to highway speeds 40-75 the car won’t rev past 4000rpms and all acceleration is lost after 3500rpms all while the RPMs continue to rise (but not exceeding 4000rpms) according to throttle position. In order to achieve highway speeds you have to feather the throttle, tricking the computer you want a different gear in order to achieve sufficient speed without high revs and the PCM killing sending fuel into the engine. You can floor it and the engine responds but will rev high without equal acceleration. If the throttle is left open allowing the engine to rev high for more than 15 seconds it will throw the "service engine soon" light on, but then goes off after you let off the throttle.

I was thinking it could be a clogged Cat, the torque converter, abused transmission, or maybe the MAF is bad.

Any insight into the issue would be much appreciated.

Additional symptoms: Terrible gas mileage, and a loud sucking noise coming from my air filter during idle

If the check engine light came on, you have a code thrown. Figure out the code and then go from there.

Sounds like it may be a misfire issue.

You maybe also have a clogged cat.

Check your coolant level. Have you fixed your UIM? Early on when mine failed it would drive around fine until you gave it the beans, then it would miss like crazy and not want to accelerate.

I've seen an issue before where the icm was having issues supplying enough spark in the higher rpm range. If you have one to swap might be worth a shot.

Edit... Now that I read it if im getting this right it sounds like a slipping trans. Probably a long shift max adapt code.

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Sounds like the trans is slipping to me. Maby the clutch disks are takeing a dump for 2nd gear. If you hammer on it from say 10mph in 1st gear dose it still slip at the 3500 rpm range. If not could be your 2nd gear disks worn out. Not enuf of them left to bite to. When you go to get on the highway at about 45-50 mph your car should kick into 3rd gear. If your going easy on it. From there you can give it just enuf gas to speed up without downshifting. It may be a pain to get on the highway but it will save what is left of your 2nd gear disks. For my car 3rd gear kicks in at about 90ish at WOT.

Originally Posted by izup69

Sounds like the trans is slipping to me. Maby the clutch disks are takeing a dump for 2nd gear. If you hammer on it from say 10mph in 1st gear dose it still slip at the 3500 rpm range. If not could be your 2nd gear disks worn out. Not enuf of them left to bite to. When you go to get on the highway at about 45-50 mph your car should kick into 3rd gear. If your going easy on it. From there you can give it just enuf gas to speed up without downshifting. It may be a pain to get on the highway but it will save what is left of your 2nd gear disks. For my car 3rd gear kicks in at about 90ish at WOT.

It feels like a long shift, until I let off the gas it will shift. I tested it by physically shifting into 1^st, 2^nd, & 3^rd gear and it exacted the same symptoms of high revs with no acceleration.

I’m frustrated because I took it to Oreilly Auto Parts to see if they would read my engine code, but because the light isn’t actually on, they won’t read it. I need a place to start lol. I might just take it to a auto shop and have them do a full diagnostic on it.

Could my fuel filter need replaced?

spark load test, check for vac leaks, fuel pressure?

DTC P0300
Engine Misfire Detected

if the pcm saw the car was lean it would probly try and "flood" the cylinders.

take your tran pan off and change the filter, put dexVI back in too, then after 500miles drain the pan agian, and fill up agian, NO FLUSHING
fix a known problem first