can a bad alt cause a surging problem?

[3100 MPFI]

I didn't really notice this until tonight (lots of fun going to get gas at 11:30 PM seeing that I don't have insurance, or inspection, or registration for that matter).

Anyways, when I was slowing down pulling back into my driveway, I noticed that when the car was surging, the lights were also DIMMING.

the alt is original as far as I can tell (original as in it was the same one that was on the car when I got it back in 2005).

The car only surges when I am slowing down to stop. As soon as I stop, the surging stops. If I tap the gas while it is surging, the tach jumps up, and it stops surging until the RPM's drop down again. When I accelerate, it is fine and does not have a hesitation normally associated with normal surging problems.

I didn't notice it before, but once I had the lights on, i saw that not only do the lights dim, but the gauge fluctuates as well.

Is it possible that the alt, and my surging problem are related?

[TazMan]

I know when I would jump another car with my 92 GP it would start surging as soon as I hooked up the cables but it was very slight. My alternator was also a little weak. Maybe these cars do this when the alternator is weak and the power drops a little low. When you stop all your brake lights come on and you noticed it at night so I assume your headlights were on too. Do you notice it in the daytime with your accessories off?

[3100 MPFI]

yes, it does. I didn't notice the voltage before last night, but it does as well. Sometimes the surging is REALLY BAD, and sometimes it does not surge at all.

In the next couple of day, I think I will just go ahead and replace the alt and see what happens.

[Sh3aNz0r]

could also be a bad TPS or IAC. my 1994 was doing that same thing, i replaced the alt and was still doing it, replaced the tps and IAC, and she strated running like a bute

[3100 MPFI]

the TPS and the IAC are NEW. I did them when I thought the DIS was going out (which it was).

Tonight, on my way home, I noticed when I cam to a stop that the VOLTS gauge was hovering at about 10.5 volts, then slowly started climbing back up. I think it is gettin gold, so I will just go ahead and do the alt (tomorrow if it does not rain..... 60% chance of that). I might also check the TPS and IAC again. I have had some of my NEW sensors go bad on me. Like the first DIS I bought. Once it warmed up, it would shut down 2 cylinders at a time. I ended up just stilling my 3100 DIS on there. Once again, I think I should check all of this out.

I think I will also pull the throttle body and clean out the vacuum passages, as well as the idle passage.

Does anyone know if the TPS is the same between the 3.1 MPFI, and the 3.4 DOCH? I know the 3100 ones is different. The twin cam is the only one that I have spares of.

[3100 MPFI]

nope. I looked them up. Maybe I have one of my old 2.8 throttle bodes laying around somewhere. Then again, it is only like $20 for a new one.

[gpse3400]

FYI I just replced the timing belt tensioner braket, thank you!!!! I ran the motor to verfiy th etimng was good and strted uo fine but as I ran it the engine started to mis fire. 1 cyl then 2 then 3 and its was running very bad. I then completed the job andran the serpentine belt and it ran just fine. htere is a voltage reqirement natually. I think the tdc is like 11.5 volts. the pushrod probably alittle less