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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
cant 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 vehicles 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 computers attitude its time to change the computer,
it has internal problems.
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