1990 Oldsmobile Driveability and stalling problem

MRBEAUMAN3

MEMBER
1990 OLDSMOBILE CUTLASS
6 CYL

I have a 1990 Oldsmobile Cutlass Ciera V6 that has had a problem for a while now that I can't seem to pin down.

When I start the car and it is in closed loop, it seems to run with minimal problems, only some minor missing of the engine.

I will drive down the highway for a while and after the car warms up it will start to act weird, such as missing to the point where I can feel and hear it. It also seems to happen when changes in the gas flow happen, such as when decelerating or accelerating. It is also a problem for keeping a steady speed cause I can feel the car misfiring.

Another symptom I have is when idling, mainly after driving for a while, it will have a loping erratic idle, and the RPM's dip so low sometimes that it seems to want to stall, and one of the ways that I can deal with this is to throw the vehicle into neutral and the loping idle will turn into a very rough idle with the engine shaking sometimes.
Also related is when I lightly accelerate from a stop some times the vehicle will stutter like some one is******** the front of the car over and over.

Another symptoms that I have seen is that when I have the vehicle in park and the engine turned on, and I rev the car suddenly, the vehicle will stall. I have to rev it gradually in order to keep it from stalling.

Another Weird problem I have that may or may not be related is the fact that while I'm driving at night and I hit speeds between the 65 MPH marker and the 70 MPH marker, my car will start to buck and the headlights begin to flicker. It does this randomly at other speeds, and very infrequently, but between those speeds I can get it to do it consistently.

I am really stumped by this problem. Any help would be appreciated!

Thanks

3 Replies

CARADIODOC

MECHANIC
33,916 POSTS

Try driving it with the small plug on the side of the generator unplugged. If the running problems clear up, replace the generator AND the battery. Since the 1987 model year, due to their design, GM generators develop huge voltage spikes that interfere with computers and sensor signals. As the battery ages, it loses its ability to dampen and absorb those spikes. Those spikes often destroy the diodes and voltage regulator inside the generator leading to repeat failures.

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Monday, July 4th, 2011 AT 8:22 PM

MRBEAUMAN3

MEMBER
7 POSTS

Thank You for the prompt reply. Now I have recently had the alternator replaced like last year and should still be under warranty, however the battery is fairly old and HAS NOT been replaced in a while. Would a brand new alternator cause this problem you are describing, or would replacing the battery fix the issue?

Thanks!

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Monday, July 4th, 2011 AT 9:25 PM

CARADIODOC

MECHANIC
33,916 POSTS

First see what happens when you disconnect the generator and drive the car. If the problem is still there, then there's no sense in pursuing my line of diagnosis. You may want to charge the battery first for an hour, always on the lowest setting for old batteries. The pulsing current from battery chargers causes the plates in the battery to vibrate. At higher charge rates that vibration is worse and can accelerate how quickly the lead flakes off the plates.

If the problem clears up, I would try a new battery first. These generators develop huge voltage spikes and if that's what's happening, that suggests yours is still working and doesn't need to be replaced again.

If the problem is still there with the generator disconnected, I don't think a new battery will help. I always suggest the battery / generator first because it is such a common problem, but you might also consider loose or corroded ground wires. In particular, I read a lot about people finding poor grounds inside the car where the wires are bolted to such places as the firewall and behind the side kick panels. Look for any under the hood too. Sometimes it's faster to just take them off and clean them up with sandpaper than to try to use voltage measurements to find one bad ground. If you do that, shine up the terminals AND the body sheet metal where they attach.

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Tuesday, July 5th, 2011 AT 8:22 PM