Crappy idle, gauges going crazy -- HELP!

[v8unleashed]

I've got an electrical problem I need help with. 2000 Trans Am.

On my way to work the other day, a couple of times out of nowhere the gauge cluster would pop, everything would go to zero, then peg, then the car would go back to normal with all of the lights on like when you first start it up. It's almost like the whole ECM was reset, since even the SES light went off (and that's been on for 50k miles). Gear changes and bumps did not appear to be the cause of this.

Then yesterday morning, the car idled like crap, kept dying on me unless I had my foot sightly on the gas. I cleaned the MAF, like I normally do when I have this problem, and the problem went away temporarily.

Today, trying to go to lunch, and the car is idling poorly and dying again, and then suddenly the gauges do the pop thing again. TPS, IAC, things like that only affect idling, and would not cause the electrical problem. I would think that something like a loose ground would not cause the bad idling.

Clearly, something electrical is going on. However, the problem is intermittent, so it's hard to diagnose. I just went out and drove it around the parking lot and it was perfectly fine. Battery, connections, alternator are all fine, and brand new. I looked for anything loose or broken, like a ground, but didn't see anything.

Any ideas?

[SMWS6TA]

have you had the intake off? there are 3 grounds. one on the pass head and 2 on the drivers head, both on the back side of the head.

You also have a ground on the fender well next to the battery.


Are the grounds and terminals free of corrosion?

Have you check the ECM to see if the harness is loose?

[blackcar]

The bad idle may not be part of the issue.

If the ECM did reset you are going to have a bad idle until it has been driven some, for the fuel tables to fill back out.

[pajeff02]

^^ This. Any time electrical power to the PCM is interrupted the engine is going to run poorly for a bit on start up.

Scott's suggestion to inspect the grounds is sage advice. If there has been any work done lately, go over that area of the engine bay and look for any damage or something left loose. Also, on stuff like the MAF, unplug it and inspect both side of the connector for loose or bent pins, or corrosion. If you find nothing there, disconnect the battery and you can carefully remove, inspect and reinstall the two large harness connectors on the PCM. For giggles, also check your "ENG SENS" fuse in the underhood electrical box. Let us know what you find.

[0rion]

when reading your post the first thing I thought of was a corroded battery cable. That's what it sounds like but you say you've checked those cables good? I've seen them corroded under the sheath too so inspect the ends of the wires good to see if they're green. I would then start looking at the ground from the battery and the grounds on the back of the head. Wouldn't hurt probably to pull the ecm connectors off and look at those pins to make sure you don't have some corrosion in there.

[v8unleashed]

I think "blackcar" hit the nail on the head, I am betting the crappy idle came from the ECM being reset.

I checked many of the things you all suggested, didn't see anything abnormal. But I have a theory. And I have driven the car over 200 miles this weekend without incident.

I have kept the radio turned off. A few months ago, the antenna mast got bent, then broke, then fell down into the spare tire well. If water got down in there, I could see it shorting out the radio. I wouldn't think that would short the entire car, but I guess anything is possible.

Anyway, 200 miles with the radio off and no problems. I will take out the spare tire this weekend and see what's going on in there.

[blackcar]

Let us know what you find.