97 lumina engine acting erratically.

[aptivaa12]

1997, Lumina, 3100
History of the vehicle is not known until 106,000 when I purchased it. I bought it from my grandmother but she did'nt keep records. Has ran fine until 120,000 miles. Regular maintainance, no engine light but it does work. Only symptoms are ocassional problems which is while accelerating it hesitates significantly, up or downhill, or at higher rpm's while idle. I cannot pinpoint whether it is during hot or cold weather. Car does'nt have a Tach so dont know the RPM'S it does it at. And it does it only after the engine seems to have warmed up and only above 35 mph. The engine appears to die while driving or idleing if you press on the accelerator half way or more. Does not appear to happen every time but becoming more common. In the last month I have put a new battery, alternator, harmonic balancer, fuel filter, air filter on it. But that was just for regular maintainance. I have'nt done any troubleshooting for this other than taking it to autozone to make sure there was no codes lurking without lighting up the check engine light. Any help would be greatly appreciated.

[maxwedge]

Welcome to AF, check fuel pressure. Also a full scan to check sensor inputs is called for.

[manicmechanix]

Has the plugs been replaced yet? The injectors on the 3100 like to get clogged up. You can try running a bottle of Techron fuel system cleaner in the bottle that treats up to 20 gals and see if that helps. The injectors probably need tested and cleaned through the rail.

[aptivaa12]

Ok as an update, it has a new catalytic converter, new fuel pump and still no fix. So I am going to try manicmechanix's idea of the the injectors. Also I did put the techron through with no help. Any more ideas would be greatly appreciated!

[jeffcoslacker]

I had very similar symptoms when the TPS (throttle position sensor) went bad on my '97...

I had dropouts on accelerating, random high idle, sometimes it would upshift late, winding the rpms too high and shift hard.

Didn't set code until it got real bad.

Three torx screws hold the TPS to the throttle body...I noticed when I took it off, it had a slight rattle in it when shaken, like a bad light bulb. The new one did not.

After installing, and idle relearn, it was fine.

Cheap part, might try it if all else fails...

[jeffcoslacker]

PS mine went out at 120,000 also, come to think of it....