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Jim Grant Tech Tips Jim Grant Tech Tips
A collection of helpful articles based on reader submissions
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  Jim Grant's Tech TipsJim Grant's Tech Tips
Below is a collection of Jim Grant's Tech Tips sorted by Vehicle Make. These Tech Tips were answers to questions submitted to Jim by ALLDATAdiy.com users over the course of many years.
If you have any questions, please feel free to email us.
 
 

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  Jim Grant's Tech Tips

'90 Oldsmobile Cutlass Ciera

Q: My ‘90 Oldsmobile Cutlass Ciera always ran great, it has just turned 100K. The car now (in the last 4 months) started to buck at all speeds, intermittently, sometimes 1 time every 2 days to 8 times in a row. When this occurs, all my panel lights come on, just for a moment, and then go off, and the car continues to run fine, but sometimes the check engine light stays on. The other thing that happens is the speedometer goes nuts from 0-90 swinging crazy, and that too goes back to normal after a few minutes. The last thing is the idle-it is perfect, too low and stalls or races to the point of lunging forward at a stop sign or light. A complete tune up was done and the computer check done and found no codes. I heard the computer can’t hold codes like the newer ones in late model cars.

- Carl S.

A: It sounds as if your computer is getting scrambled. I would suggest checking the computer ground wires. The major group of ground wires is located at the bell housing of the transmission on a bolt that holds the transmission to the engine. Check for the bolt being loose, wires breaking or corrosion. For you vehicle’s computer to think right, it has to have a clean power supply and ground. If the ground circuit has a problem, it kind of back feeds the computer causing a voltage build-up on the circuits that just causes the computer to wig out. All it takes is one bad ground wire to cause a pile of drivability and running problems. The computer can get so confused by a bad ground that it will turn the check engine light on but there will be no codes present. All you have to do is hit a bump, shift gears or shut a door and the vibration will cause the ground wire problem to change. When this happens the computer changes the way it is acting too. If the wiring checks out you may want to give the computer a love tap. With the computer hanging by its wiring and the engine running just slap the case of the computer. If there is a circuit board problem, you will hear and likely feel the change in the way the engine is running when you slap the case. If a slap changes the computer’s attitude it’s time to change the computer, it has internal problems.

 
     
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