Destructimus

I've been having some weird electrical problems lately. The car backfires on a regular basis, but usually only after I take my foot off the gas. Sometimes at stop lights it will suddenly drop to below 400 rpms and then go up again then back down and up etc. When this happens the lights dim and I can even tell it burns rich so I know theres a voltage problem somewhere. I got my battery and alternator tested and they tested fine even though this problem wasn't occuring at that exact moment. Also, I have a tachometer that allows you to select the color it displays and it changes on its own now, frequently and for no good reason. Does anybody have any idea what the hell is going on? It's getting worse too.

Lucid

iTrader: (4)

How does the voltage level show when you are driving it? Does it stay steady at 13 volts or does it go down to around 10 volts and stay there.

The most important things to look at when you are testing the alternator are the voltages across the battery terminals when he car is running and the amperage that the alternator is putting out.

You can check the voltage with a hand held voltmeter. The only way to keep the battery fully charged is for the alternator to provide voltage in EXCESS of 12 volts, so look for something like 13.5-14 volts.

The amps are harder to check, one of the car places should help. Try to keep an eye on the amps while they are checking it or ask them to watch it for you. If its putting out very low amps at idle, its not giving much juice and its going to drain it dry.

If these check out ok, you need to look for a short.

Destructimus

I checked and my alternator reading is right where you said it should be, except for the instance where it revs down like I said. In that case all my gauges go down a kick though. When I got my battery and alternator checked at murrays and auto zone they spent some time with a pretty fancy looking thing hooked up to it, had me rev my engine a few times, etc. so I can't really expect them to have not checked the amperage. Anyway, I have a voltmeter here so to check for shorts should I just go wire to wire and hook it up to the ground, and see what readings I get? But if I had a short wouldn't my battery be dying on a regular basis? It never has. Thanks for the reply by the way.

1991ON20's

hey boss....i had the same problem and here was the diagnosis.

First off.....i had my new motor installed by some punks in Nashville,Tenn.

They wired up 90% of the car right. I paid them for the install(1400.00) AND drove off(i didnt know any better). I get on the Interstate heading west bound for Utah. All of a sudden like around 45 to 60mph im backfiring all over the place. My rpm's DROP Rapidly then come back up. THe Stop light scene was the worst.....backfires, rpm drops and cut-offs. SOOO embarrasing.

But i put my car on a transport after paying 1400.00 to some "JOES" to do a motors install. When the car arrived to Utah my mechanics simply Ran an OHM Meter under the hood. ----> My car wasnt grounded properly<----. YOu my friend must have a loose ground somewhere. Or even ground wires reversed in some cases.

Check the local chevy dealer and see what the proper OHM reading should be on an ALL stock 3rd gen. Yours will probably read HIGHER ohms.

quick senario....my mechanics grounded the car properly....BUt last week i did and A/C delete on my 91rs. After pulling the 2 wires off the Ac compressor my car stared dropping RPM's again. WTF? So i simply regrounded those wires and my car was back to normal...NO backfire...NO rpm drops.

and my battery was tested also at an autozone and altenator tested...they where definitley working. ITS a ground ISSUE.

did you remove anything? you might even get a Check eng light....

hope this helps....

Destructimus

Thanks a lot man that helps. I'll look into it for a while but my insurance runs out in about three weeks then I'm going to give it some TLC all winter. If I don't figure it out I'll take it to a dealer.