Hi-I am new to this but I am hoping that someone can help me...

I have a 98 cavalier with 135,000 miles on it. About a month ago I was driving down the highway when all the needle gauges dropped suddenly and then instantaneously returned to normal function. This happened once more since then while waiting at a red light.

Since the car was otherwise running properly and had just passed inspection, I assumed it was fine... Until last night.

While driving at any speed the car seems to run as normal. However, when you stop at a red light the RPM needle goes up and down and the car behaves as if it is going to stall.

Any suggestions as to what this might be and how much it might cost?

Your insight and advise is greatly appreciated.

Regards
:confused:

. Test/replace the Ignition Control Module (ICM). Here's what it looks like and costs:

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AutoZone can test many ICMs for free.

. Test/replace the coils, which AutoZone can do for free. Here's what they look like and cost:

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My bet is that the ICM is bad (cause) and the erratic tachometer needle reflects this (effect). A failing ICM could also explain erratic behavior in other gauges (e.g. voltage, ammeters, and oil pressure). ICMs are problematic components and, if you are going to keep the car, I would replace it. I recommend doing this every 120,000 miles or 10 years, whichever comes first. Since you need to remove the coils to get to the ICM, this is the logical time to test them.

. Replace spark plugs (AC Delco only) and fuel filter, if they have not been done recently.

What you are describing sound like the instrument panel cluster (IPC) is on the verge of failure, at least that function. A faulty internal circuit board is the likely culprit. The cluster will probably need sent to an authorized repair facility (not just anyone can repair an IPC).
The cost will vary, but it will need to be done by a facility that can reprogram the theft-deterrent system once the repaired unit is reinstalled.