First, sorry if this is in the wrong section.

My dad's truck, a '96 GMC Sierra (5.0 V8) is having odd problems. When turned on, it's fine, until it's given gas, which results in an idle surge. Also, the oil pressure, temperature, and voltage meter gauges all move and fluctuate with the idle, which goes up to 2k RPM. The battery light flickers on and off, but the battery is fine, along with the terminals. The check engine light does not come up. It tries to die, but my dad will step on the accelerator to keep the RPM's up. Can any one here help? Thanks in advance.

-Jesse

 

I have seen similar problems with a bad alternator. Also check the ignition module.

I would say fuel pump or cats, but they wouldnt cause your gauges to move. BTW, the oil pressure guage is supposed to move when you rev it.

 

The alternator is relavtively new, as we replaced it over the summer. I know that the oil pressure gauge is supposed to move, but it moves the exact same time/distance as the rest of the gauges that move. That's why I thought it was a bit odd. We did consider the fuel filter, though. Thanks for the help.

 

Alternators on these trucks are known to go. If you replaced it with anything BUT a brand-new-in-the-box GM AC Delco alternator, then it's probably bad. I have a '98 Chevy K1500, and my mechanic works on a FLEET of Chevy trucks for a company, and he says the ONLY alternators that are any good are the GM AC Delcos, brand-new, no rebuilds.... They say even though the GM one isn't that great, the rebuilds and aftermarkets are even worse... This is typically true of most parts. BTW, it's not the mechanical parts of these alternators that go out. It's the voltage regulator. Goes out way before the brushes and actual mechanical parts, at least on the AC Delcos. My first alternator went from perfect voltage to ZERO in an instant......

On the other hand, my truck ran just fine even WITHOUT a working alternator.... I actually drove it about 60 miles with no working alternator whatsoever... Zero volts output. I actually didn't even realize the problem until about 25 miles of driving when the voltage light finally came on and I noticed the volt gauge was very very low... So, I'm not sure if an alternator problem would cause the engine to fluctuate like that.

I wish I could help more, but my '98 has only required regular tune-ups, oil changes, a fuel pump and an alternator.

BTW, fuel pumps go frequently on these too... maybe an issue? Can you check your fuel pressure?

-Michael