High Speed Hesitation (frustration!)

[ChicagoMatt]

I'm desperate for help on this. My Grand Am, as of 6 weeks ago, hesitates at speeds at or above 45 mph. it is sporadic and not constant even when it does happen..somtimes worse than other times and always worse the faster I go. RPM's jump up a few hundred to nearly 1000 at speeds of 60mph or faster during the hesitation. No trouble starting, no trouble accellerating..especially at low speeds..idles perfectly.

So far have had...
ignition coil fixed (it was bad)
spark plugs, etc done/replaced
fuel filter replaced
IAT (Air-Temp) Sensor replaced

Car runs better..but still has annoying problem...then the belief was torque converter.

Brouth it to trans place..highly recommended and they were great guys. Owner actually drove it home with scanner on it. 30 miles on expressway. Came up as brake switches while driving. Put meter on it back at shop..no power. Took them apart, contacts were bad. Yeay..fixed, right??

Nope!!

Still friggin does it.

Does anyone have any clue what this possibly could be??

I'm starting to be afraid it is the computer itself.

Oh..trans has been flushed and serviced through all this as well.

No codes come up at all pointing to trans or fuel pump..so you know.

Thanks in advance for helping this desperate man!

[ChicagoMatt]

Should mention... 2000 Grand Am SE 4 Cyl is my car..d'oh..forgot to mention that!

[shannoncouch]

Hey,
My 99 Grand Am does the same thing. I took it to the garage where they ran diagnostics and couldn't find anything wrong. It only does it after driving for atleast 20 minutes and while going up hills. Also while driving high speeds. When you give it more gas to keep up the speed, it hesitates, the RPM's bounce up and down and the only thing to make it stop is to give it a ton of gas. My dad, who is a mechanic, believes it to be a problem with the fuel pump itself. I haven't felt like taking it to the shop again because I am planning on getting rid of the car ASAP. I've had more problems with this car than my old 89 Mazda! Good luck finding out what is wrong with your car, just wanted to let you know that mine does the same thing...

[grogan5]

Check for arcing of plugs. Mine was doing the same. Had to replace plug boots. Eventually led to head gasket failure on my '92, before we found the cause.

[ChicagoMatt]

Nice to know I have some company in this. I did have the spark plug boots replaced and the spark plugs..had platinum spark plugs put in, etc. So that is done. Had that done at the same time as the ignition coil. As far as the fuel pump goes..I've bounced that idea off a bunch of mechanics and friends who know lots about cars and we all wonder why it wouldn't give me any probs starting, accelerating, etc and only be sporadic at high speeds. Drove it last nighg 26 miles on the expressway..didn't hesitate at all. Some days it is good..some days it is bad. I can't wait to never own a Grand Am again. Thanks for both your posts and feel free to you and any of you out there to post and bounce ideas off of me..I can use the help!!

[Jpit]

I had a similar(but not the same) issue happen on a mazda 626 of mine. It would stutter/hesitate at 3500 rpm. Turned out it was just a dirty mass airflow sensor. Cleaned it with brake cleaner and all my problems went away...at least all my car problems..

[jay02]

i know its been awhile since the last post.. but maybe we can solve this...
I'm having the exact same problem... some of the things ive heard it could be are: the coil pack, catalytic converter, injectors, plugs... any other ideas anyone?

Jay

96 GA SE 2.4L