charlie6178

iTrader: (2)

I have my 92 L98 5.7 camaro, and I’m chasing a gremlin that I cannot seem to pin down. Looking for some help hopefully! If you fire the car up dead cold, the voltage gauge reads about 13.7-13.8, and if you check the charge wire at the back of the alternator it’s right at 14.0 volts, and all is well. Now if I drive it 15/20 min, get it up to temp, and come up to a stop the voltage gauge will read 12.9-13.0 but if I jump out and toss a multimeter on the charge wire on the alternator it’s still a 14.0. Now if I keep driving the gauge will read about 13.0 or dead straight up and down on the needle. Then come to a stop and it will bounce around like an oil pressure gauge when on and off the throttle. Now for the real annoying one... as it gets hotter and hotter, or under hood temps rise, then it will die, but only off the throttle, and generally when coming to a stop, or when load changes in a parking lot, etc. I feel like the 2 problems are related, and the reason I say this as it won’t die until the voltage gauge starts bouncing around, and when it does die, it’s when the voltage does a dip or drops on the gauge. But... if you have a multimeter on the charge wire while all of this drama is going on, the voltage at the alternator does not fluctuate at all.

The first time this happened, I think “oh no problem, needs an alternator” so I proceed to replace the alternator, and battery. Problem is still there. Warranty the alternator twice, and put a new alternator plug on the harness, and we are still in the same spot. So next move “it must be the junk parts store alternator!” So we go get an OE replacement from the dealer for $320 some dollars. and try another new battery. Problem still present. So lastly I can’t get charging out of my head so we have a great rebuilder in Portland who is very reputable, so I take him the alternator and he tests it, tests it hot, pulls it apart, checks all tolerance, and all seems great. So I feel the alternator, and battery are good!

My next idea is ignition issue?? I’m wondering about the coil, ignition switch, distributor, or wiring to one of those??? The distributor is only a few thousand miles old at best, but it’s also 12 years old, and I cannot remember if it was a GM replacement or an aftermarket.

has anyone else had this issue?

Other things I’ve ruled out are, fuel tank pressure, fuel pressure, injectors.

Vader

What you have determined is that the in-dash voltmeter cannot be trusted as a precision instrument. It only cost $1.62 when is was built into the cluster 30 years ago, and since it isn't made of wine it probably didn't get any better.

There may be no problem with the charging system at all. It may be useful to test wiring and connectors. After heating from passing current, connections can become resistive. Examine the wiring diagrams and determine the connectors between the alternator/battery and the distributor (and coil) and monitor those points for voltage drop. Don't overlook ground connections.