2001 Mitsubishi Galant - electrical and stall issues

Maintenance/Repairs
, ,
1

Let me give you a bit of background before I get to the recent problem.

5 weeks ago I needed a jump start because the battery was drained. Also, the terminals were really corroded. Took it to Autozone where they cleaned the corrosion and tested the battery. Battery (about 3-4 years old) tested fine. The alternator tester was broken so I didn’t know about that. But they guy said the corrosion could have been keeping the battery from making a good connection, so we figured that’s what caused the problem.

Everything was fine for 5 weeks until yesterday. My car sat unused for about 4 days until I went to start it up yesterday evening. Battery was completely dead. I got a jumpstart, but noticed the car idling really low, like around 500 rpm. I wasn’t able to drive it around long because I was late for a meeting. So I drove for 10 minutes to the meeting, then got another jumpstart afterward and took it to Autozone.

The low idle caused me to stall twice. I eventually had to shift to neutral at stoplights to keep the engine revved high enough so it wouldn’t stall.

Autozone checked the battery and alternator and said both we fine. So I don’t know why my battery died in the first place. And now I have this low idle issue added on. I haven’t driven it since last night, so I don’t know if it’s still a problem today.

So, my questions are: what could be causing my battery to drain or not properly charge if not the alternator or battery? And what might be causing my idle to be so low? And could these two be related?

Thanks for any advice!

2

I think you have two separate issues. First, I doubt the battery is any good. It sounds like it has an internal short that may be intermittent. When you jump started the car, the battery starting drawing a large load due to the short, this load caused the idle to drop.

The computer did not pick up on the excess load, which is your second problem. That is because the computer did not know it was supposed to. It gets the information from either the TPS (throttle position sensor) or idle position sensor. That can be caused by the throttle not closing enough to send the signal. This is often due to a dirty throttle body or mis-adjusted throttle stop screw. It can also be caused by a bad IAC (idle air control) motor.

Start by having the battery load tested after a full charge.

3

OK, that’s some good information. Thanks!

Assuming it turns out to be the battery, what, if anything would I need to do to fix the idle issue? Since it wasn’t a problem before the battery drain, would it go back to normal if the battery issue is solved, or is it going to stay like that until an underlying problem is treated?

Thanks again!