Headlights causing a stumble.

[jimberg]

I discovered the weirdest thing yesterday. On my way to work, my engine was running perfectly. On the way home, it kept bucking and missing while at highway speeds. It actually did this on a previous night, and ran fine the morning after. Since it ran the morning after, I just figured that my computer was relearning the air/fuel ratio from when I changed the plugs the previous day and had finally adapted. The pattern is this: Runs crappy after changing spark plugs on the night I changed them. Runs fine the next day. Then runs fine the morning after that. Then runs crappy that night. The only thing different is that the headlights were on. Since there was still a little light left, I turned my headlights off to see what happen. Sure enough, the problem stopped. When I turned them back on, it came back.

Another thing I noticed with the headlights is that the water temp gauge reads higher by about 20 degrees. A while ago I used to think I was actually running hot, but now I know that something must be going on with the reference voltage used for the sensors or something. My only guess is that since I was running underdrive pulleys for a long time so they were not allowing the battery to fully charge. I installed a new, stock alternator and removed the underdrive pulleys.

Could the battery still be weak because of all the abuse it took from not getting fully charged, or do you guys think it could be something else? The car starts fine and all, but whenever I run the fan or turn on headlights, I can see the voltage gauge drop a couple volts. I've checked the grounds and they seem okay. The battery goes to the block and then the block has a strap to the chassis.

I may try to have the battery replaced, but since it really isn't dead, I'm not sure if they will do it under warranty.

[Gearhead999]

I would make sure the grounds are good. Take them off and clean them up. No paint or rust at the connections.

Next have the battery tested. Then have the alternator tested and see what its output is with a load on it. You may have a weak alternator, bad diodes, that isn't running up to snuff.

[jimberg]

Since I've replaced the alternator and checked the grounds, I guess it must be my battery. I'll take it and have it replaced. It's not fun not being able to smoke people at night.

[GhettoPop]

i had the same problem after i replaced alternator. the battery got the hurt put on it real bad with the bad alternator so the battery still gave me problems even with the new (rebuilt ) alternator. the battery could no longer hold a good change as you can drain the battey down to nothing only so many times. i ended up replacing the battery. on a side note, that REBUILT alternator ended up lasting only 6 months, what a piece of sh*t. i highly highly recommend a 130amp PA Performance alternator w/ lifetime warranty, for $200 it was money well spent and i have never looked backed.

[mpj76]

My car did the same thing with the temp going up a touch when the headlights were turned on. It ended up being old wiring from the battery to the starter solenoid. My rebuilt 3G has been running strong for about 5 years now.

[Capri306]

Just my .02 on top of what others have said (especially the headlight grounds), I'd check the three-wire connector at the alternator (the one with two bigger black wires and a smaller third). Replace that connector if it's the original! Those have started many fires due to loose connectors and a bad design. Part of the reason I too switched to a 3G alternator. Also, I got sick of seeing 10 volts at an idle.

[jimberg]

I guess I will be buying a 3G alternator soon. I'll stop on the way home tonight to get the connector for the alternator. It is original.

[jimberg]

It was a bad battery. I got a replacement and the volts stay above 13 when idling with the lights and AC on.

[GhettoPop]

Originally Posted by jimberg

It was a bad battery. I got a replacement and the volts stay above 13 when idling with the lights and AC on.

that is an awesome number. good stuff!