Grand AM GT 2000 V6 Weird Acceleration Problems.

[Soah]

Hey All,
I have a Grand AM GT 2000 V6, with a very weird problem. I have taken the car to 4 different mechanics including one at a Pontiac dealer ship. To no avail has my issue been resolved.

Parts replaced which supposedly was the problem are both O2 sensors, All Spark Plugs and Wires. EGR Valve and MAP Sensor, fuel filter and pump.
The last guy said it was a plugged exhaust at which point I have the exhaust off the car but problem still exists.

The problem:
Car starts fine. Idles fine. Drives somewhat fine but when I drive up to 80km from 60 to 80 the car hesitates, The RPM will go from 2600 down to 2000 then back up, and down, and up, over and over till I get up over 80. If I Tramp it up to 80 from 60 to 80 it will fart and sputter with little horsepower.
Some times during the 60 to 80 the peddle is un responsive. I can press it all the way down and it does nothing until it is to the floor then it kicks in and takes off, but not a good take off really under powered.

After driving for about 40 minutes down the high way the symptoms change. If I drive the car and make sure to stay over 100km it seems fine, but if the car drops down under 100 for example I get to a hill the peddle is again unresponsive until it drops down under 60ish, Course I put it to the floor it will take off.
If the hill is to steep the car does not have enough power to climb up to 100 and I generally have to take it at 60.
Sometimes when I tramp it, it does have the normal HP and takes off great but most times it does not.
When the speed limit is 80km, I am the guy that goes fast to 100 and then slows down to 60 then takes off again to 100 and so forth. Did this across Canada this summer was brutal.

After the symptoms change to the second scenario, if I get to a city and have to drive 20-40km, I can't. The peddle won't work anymore. I basically have to idle to the side of the road and turn the car off and then on again. This resets something and the car is back to symptoms in the first scenario which will allow me to drive in town again.

It has to be a computer thing. Any Ideas would be greatly appreciated.
Thanks

[Tech II]

What do you mean the exhaust was off the car?

There are no codes?

[GTP Dad]

Not necessarily a computer issue. Could be bad injectors or a bad throttle position sensor. Given the fact that when you hit the accelerator and nothing happens the injectors may have gone bad and are not responding to the computer. Also the throttle body position sensor may not be responding either. Start with the TPS and have the injectors ohm checked to see if they are going bad. I had a car that the injectors were warn out on and it acted just like this one. Replaced the injectors and everything worked fine.

[Soah]

Originally Posted by Tech II

What do you mean the exhaust was off the car?

There are no codes?

Yeah its off right now haha
Cut it off at before the cats cause the Mechanic though it was plugged.

Only difference is my car is loud now

I am going to weld them back on there this week. Might even do it up tonight.

[Soah]

Originally Posted by GTP Dad

Not necessarily a computer issue. Could be bad injectors or a bad throttle position sensor. Given the fact that when you hit the accelerator and nothing happens the injectors may have gone bad and are not responding to the computer. Also the throttle body position sensor may not be responding either. Start with the TPS and have the injectors ohm checked to see if they are going bad. I had a car that the injectors were warn out on and it acted just like this one. Replaced the injectors and everything worked fine.

K Ill start there see where it takes me.


Thanks a ton