ryman416

iTrader: (1)

2006 2.2 LT/SC No codes

The car idles fine until I touch the throttle, then the revs bounce severely, usually leading to stalling the car out. (checked/cleaned TB) Voltage still goes from 14.8 to 13.2 when i touch the throttle. Even without any throttle input, the voltage is still bouncing around. I disconnected my aftermarket headlights and the intercooler pump as well and still this happens. My battery charges fine but i have drained the battery by accident before, but push starting it starts it and it charges right back up. I am still thinking it is a weak battery but I don't know why the voltage bounces even at idle. I'm not sure if the battery is factory or not but i haven't changed it since i got the car, 5 years ago but only 25k miles on it. The battery can still be the factory one, which will make it 7 years old with 50k. This is why I'm thinking its the battery, but if it starts up, shouldn't the battery be fine?

Any insight will be greatly appreciated.

Note: the car behaves fine when accelerating/ cruising. It is when I take it out of gear that rpms starts to bounce, unless I perfectly ease it to 1000 rpms in gear and then put it in neutral.

insylem

I vote battery. They normally only last 5 years.

ryman416

iTrader: (1)

but once the car is on, wouldn't the alternator be the reason for bouncing voltage?

ryman416

iTrader: (1)

I just decided to drive it around the block and even though it was bouncing as i backed out of my driveway, once i drove around the block, the idle would level off at 800-1000k, even if i blip the throttle. So it seems to only do it if I'm just sitting in my driveway. But for the most part, it is drive-able. Do our cars need to "learn" the idle values? As in, driving it around lets the car know what is idle and what is not?
I also tested the batteries from my other cars and it did the same thing. I was also thinking I need a higher amp battery since I am running more accessories (gauges, radar detector, intercooler pump, aftermarket headlights) but I am still hung up on the fact that I thought the car gets power from the alternator when its on. ??? electrical gremlins make me angry.

09CobaltSS1

If voltage isn't holding steady, the voltage regulator in the alternator is the most likely culprit. It could however even be an issue with the slip rings being gummed up or worn brushes. Either way, my vote goes with an alternator issue.

ryman416

iTrader: (1)

Yeah after my troubleshooting today, I'd say its more possibly an alternator problem. I was thinking of replacing it with a higher output alternator, or the lsj alternator, since i have more things than stock drawing power, but nothing too demanding besides the headlights and intercooler pump. but if the alternator is salvageable and just requires a good cleaning I'd rather do that

insylem

Alternators do NOT put out a constant steady voltage. It's just the way they work, If your voltage is fluxuationg and fluctuates faster at higher rpms, then it points to a battery

Part of the batteries job is to smooth out the bumpieness caused by the alternator.

09CobaltSS1

Actually for this to happen at a higher rpm would point more to the diodes tha anything else. Plus the op mentioned nothing of the issue occuring at higher rpms anyway.

Now, what you're saying does havs some truth to it, but it's not 100% correct. An alternator should and will produce a reasonably steady DC output, however the AC output going into the regulator will vary.... hense the job of the regulator to maintain a steady voltage output. The output at any give rpm will not deviate much past .2-.4Vdc, even at idle.

Now as far as the battery goes, I will agree that it should be replaced one way or another due to the simple fact that he has drained it down once before. As far as the voltage swings go though, unless the battery is that low on water, it doesn't really totally make sense to cause voltage flux. Aside for the battery obviously being the main power supply, it also acts almost like a large capacitor that dampens load spikes/dips due to large power draws in the system. This however will not (to an extent) dictate the output of the alternator under normal circumstances. The voltage output can however change if excessive loads that the alternator or battery can not keep up with are applied. Granted we have no idea exactly what sort of load is on his electrical system at this point, and again yes the op did deplete the battery before, but the signs still point to the alternator getting a little iffy. Either way, the battery should be replaced regardless sooner than later. I bet the voltage will still move around though..

Question for the OP. Is the voltage bouncing when the rpms hold steady, or does it only seem to happen when the rpms bounce around on you?

insylem

I remember years ago, when my battery cables came loose. With my good alternator the headlights and voltage would flicker some, and the frequancy of the flicker would change with the RPM of the engine. I tightened up the battery cables and it went away.

ryman416

iTrader: (1)

the voltage bounces even with out any rpm bouncing. Since I'm running 60's, the voltage differences yield even more of a fluctuating fuel injection amount, which sends the car into a perpetual rpm bounce. It does it when I am at idle with no bouncing, until something happens to disrupt the idle, usually me tapping the gas.

09CobaltSS1

Yeah that was basically my main reason for asking. I was trying to see if one was a result of the other or if it was purely based on if the idle bounced around.

Either way, try starting with a new battery and go from there seeing as how you probably should have replaced anyways it to begin with and see if that helps. I still think it's more in the alternator, but at this point start with the simplest thing and go from there. Update this thread once you replace the battery just to let us know how you made out.

ryman416

iTrader: (1)

I don't think its the battery because I swapped batteries from my other cars and it did the same exact thing.

09CobaltSS1

Ahh gotcha. Yeah I didn't expect the battery to be the issue but it was the easiest thing to test first. Double check all your connections and if all is good then I would look into installing a new alternator or having your current one rebuilt.