50-75 MPH lack of acceleration

96 Grand Am SE -
Drives fine in the low gears but past 50 mph the tach drops about 500 -700 rpms when holding a speed. Then, when I slowly press the gas to accelerate... nothing happens except if feels like it is sputtering. Sometimes it starts to lose speed. Then when I give it a good amount of gas, it seems to "wake up" and start accelerating. And just for clarification the engine light is not on!

Anyone have any ideas? :eek7:

Thanks,
Kev

I would guess plugged cat converter.

What kind of engine?

Probably coil packs, when was the last time the spark plugs replaced?

hmmm well I would've said the cat, because it in the cat problem initially more noticeable at higher speeds, due to the exhaust gas velocities being lower = they can't push as hard to get past blockage. In lower gears, the engine is revving higher, so they have enough speed to get out effectively. But I'm guessing Slade most likely knows more then me about this kind of stuff, so I'll back him up - check the coil packs. If that's not the problem though, could be the cat.

What kind of engine?

Probably coil packs, when was the last time the spark plugs replaced?
It is a V6 3.1. And the spark plugs are less that 2 months old...
How do i (or can I) check the coil pack?


Also, I recently blew both head gaskets and had it repaired.

Anyone else? :sadwavey:

Well you people.
this is the problem!!!!!!!!!!!!!!!

All grand ams do that 1996+.
After 45mph if you keep it at a constant speed your tranny shifts too the 4th gear to save gas. then when you accelerate it wakes up about 1.5sec and back downshifts to 3rd. you can take this control off your pcm but it is useful for highway driving.

Your welcome

If you give it just a little gas it probably isn't going to down shift, therefore you don't have as much power because you aren't in the power curve. If you give it a bit of gas you down shift, rpm's go up and you are in the power curve= better acceleration.

Well you people.
this is the problem!!!!!!!!!!!!!!!

All grand ams do that 1996+.
After 45mph if you keep it at a constant speed your tranny shifts too the 4th gear to save gas. then when you accelerate it wakes up about 1.5sec and back downshifts to 3rd. you can take this control off your pcm but it is useful for highway driving.

Your welcome
Trust me when I say I know my car, and this is not normal and that is not the problem. It feels like something might be blocked, and when I give enough gas, it pushes past the blockage. OR!~ Cylinder misfires! However the engine light has not come on to signify the misfires...

Agitated,
Kev

too me it sounds like a block cat conv. At a cruising speed the car should not go down to 500-700 rpms no matter what gear your trans is in, that's your idle speed at a stop, it should be at the lowest at a cruising speed of i would say around 1200 rpms, since that's the lowest I've seen mine go, not to say that it couldn't be or go lower..

too me it sounds like a block cat conv. At a cruising speed the car should not go down to 500-700 rpms no matter what gear your trans is in, that's your idle speed at a stop, it should be at the lowest at a cruising speed of i would say around 1200 rpms, since that's the lowest I've seen mine go, not to say that it couldn't be or go lower..

Amen - which is exactly what I casted my ballot for.

too me it sounds like a block cat conv. At a cruising speed the car should not go down to 500-700 rpms no matter what gear your trans is in, that's your idle speed at a stop, it should be at the lowest at a cruising speed of i would say around 1200 rpms, since that's the lowest I've seen mine go, not to say that it couldn't be or go lower..
Ok.. so the sputtering is proabably a blocked cat or maybe the coil pack... Is this soemthing I can fix or does it need a mechanic?

I would still say the Cat since You mentioned about highway speeds and the car not wanting to go, Mine did the same thing, Mine would "sputter" around 40 mph but at 60-70 I was flooring it and the car wouldn't do anything, eventually it got to the point my car would not even go, it would just rev. As far as replacements go You can do the coil pack with little or no problem ( never did one myself though) the cat I would probably say you will have to take it to someone, since you have to cut out the old and weld in a new one, unless you have the equippment i would say no.

black halo...just out of curiosoty did you ever get this problem fixed? Ive been having the same problem for about 4 months now but dont have the money to get it fixed. Ive got a 94 with the same engine so im guessing weve got the same poblem. Im almost certain its my cat since it rattles pretty badly from teh cat area and ive pulled a few small shards of metal from my tailpipe (which im guessing is the honeycomb from teh cat).
Im just worried that this isnt all that is wrong with my car, since it is an unreliable piece of crap. Only has 58k miles and runs like i would expect a car with 258k to run.

Just wondering if and how you took care of the problem?

This has happened to 2 of my cars now. Start with the spark plugs, then test your coils. You can test your coils using an ohmmeter, and any repair manual should tell you how to test it. From my understanding the problem is that you aren't getting enough power from the coil to create the spark needed to burn the fuel. the result is a lack of firing all together, and the fuel is pushed out the exhaust and into your catalytic converter. If you let it go long enough, you'll lose your cat, maybe more. the coils are easy to find, and easy to fix, you'll find them inside the ignition module housing, right on top of your engine.