Rising and falling idle

Asked by Mar 14, 2010 at 03:46 PM about the 1994 Chevrolet Blazer

Question type: Maintenance & Repair

I have a 94 Blazer, 4 door, Tahoe package, I have suddenly lost the electronics to the overhead lights, mirror controls, rear power windows, and engine tempature guage. It also now has uncontrolled idle, so low the while stopped at a light it will try surging forward, or just die (no sputtering, or shaking ) engine just stops. Today I started it and the idle was so high the blazer traveled at 30 mph with out touching the gas. The transmission seemed as if it would not fully engage till I was over 30 mph.
I disconnected the MAP Sensor, thenthe positive on the battery, replugged MAP Sensor and then hooked battery back up. I was told that will reboot the brain. That fixed the high idle, but in less then a mile it went back too low and died when I stopped at a red light.

Is this a bad Map sensor? A bad BCM or ECM? I understand this year has both a BCM and ECM.

Also any other suggestions as to what the problem may be or how to fix it?

Thanks
Kevin M.

1 Answer

25

After making sure a full tune up is recent I would start checking ground wires. Pull up a schematic of the wiring and start looking for loose or corroded ground wires. Any codes?

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