Battery was dead for months, now the idle is freaking out!

I spent 5 months in Afghanistan, from November to April. In that time, I paid a friend to keep my car in her garage and start it every once in a while.

Well, the battery died sometime in December (not sure how, brand new battery) and she never bothered to jump it for me, so it sat like that until I got back.

When I first jumped it, it idled really high, and then started to kind of modulate between 1000 and 2000 RPMs about once per second and this just continued. I figured it was charging the battery, but I took it to my shop so they could give it a once over before I drove it around.

They said the car needsto learn how to idle again. That I need to let it sit and idle for a while, and then drive it around normally and it will just get better, but it’s not getting better.

So when I let it idle for 10 minutes:

0-1: Idles high, 1500-2000

1-7: Long, loping between 1000 and 2000 about once per second.

7-10: Short loping about a quarter second in length.

Idle is so high that it will accelerate me down the street, shift up and continue accelerating. The highest I’ve seen it do this is it got me in 3rd gear going 35 mph from a dead stop on idle.

Symptoms: crazy idle, rough shifting, high idle.

I think the problems began with the jump start. Were the jumper cable connections ever reversed? Even for a split second? I think the problem is with the ECM. You need a good mecanic to get this problem sorted out for you. Please list your model year when posting a question because it makes getting the answer a lot easier. Thank you for your service to our country. Are you military?

1998 Honda Accord EX - 2 Door

Gosh, I had the year in there at one point and edited it out.

No, I know when I was jumping it that the cables were never reversed, though I can’t guarantee that the friend who was storing it for me didn’t try that at some point. Do you think I need to take it to the dealership? Is there a way to just reflash it? I took it to the dealer last week and they suggested (like my normal shop) just driving it around, but that seems ineffective. Plus, these guys would charge me $100 just for glancing in the direction of the car, which gets my hackles up.

No, I’m not military, I’m a civilian software engineer. I was over there to help an Army Brigade field a new radio system. It was a great experience and really gave me a whole new perspective on what it’s really like out there for our fighting men and women.

If driving it around is not a problem then I would try that for a while. Have you disconnected the battery yet? Sometimes disconnecting the battery for an hour can clear some oddball problems with the ECM. It’s worth a shot. Just disconnect the negative cable. The radio presets will be lost and the clock will have to be reset. Did you have the computer codes read?

It could be that your IAC needs to be cleaned.

I’d clean the IAC as tardis suggested just b/c that is easy and cheap. Also check the wiring for the IAC.

But I’d also be looking for a vacuum leak - probably a fairly substantial one. Check especially for any sign that rodents have been around under the hood while the car sat - they chew all sorts of things including vacuum lines and wiring.

My mechanic did clean the IAC and checked for vacuum leaks and didn’t find anything. So I think I’m going to unhook the battery for a couple of hours and then hook it up again and let it idle.

My problem may have been not giving it enough time when I first jumped it again, because I almost immediately started driving it around.

[i]Update: found this post on a Honda forum about a reset procedure for the ECU. I am going to try this tonight and will report back if successful.[/i]

Has the battery been checked, the voltage should be between 11.9V (0% charge) to 12.6V (100% charged). Sitting that long with a parasitic drain might have killed one of the cells, if so the battery would have less than 11V.

Trying to charge a discharged battery is hard on an alternator, trying to charge a bad (dead cell) battery will kill the alternator. Use a battery charger to recharge the battery, then try it in the Accord.

I can’t speak for Hondas, but when the battery in my 2000 Blazer was partially discharged (12.1V), the truck would start and run. However the idle was a couple of hundred rpm higher and the torque converter lockup would not engage.

Good luck and thank you for serving,

Ed B.


The battery was charged up by the shop, though I haven’t checked the voltage on it. I know exactly where my multimeter is, though and I’m going to check it when I get home from work today.

  • Will

Don’t know about Honda but on my Olds there is a specific and strange relearn procedure to go through that is only in the factory manual. Something like key on 10 seconds, off etc. push gas pedal in while brake pedal is on, etc. You might want to give the Honda service dept a call and ask them if there is another relearn procedure. Hope you didn’t pay her much.

All right, I checked the battery voltage and it had comfortable 12.5 Volts. I performed the ECU reset procedure of disconnecting the battery, letting it sit for a few hours, reconnecting and letting idle for ten minutes and it’s still acting up.

I may be down to hitting the dealership, which is not an attractive prospect.

old thread, but wanted to add for people like me googling for answers. Had a dead battery on my 97 grand Cherokee, guy from AAA came, jumped it, and mentioned that with these late 90s Jeeps, among other cars, the ECAM relearned idle technique really slowly and they get touchy as they age.

He suggested letting it idle 45-60 minutes, turn on the AC for a bit, watch your idle, then gently give it gas, let go, wait, repeat, and then drive it around for a bit.

I made the mistake of only letting it idle 10 odd minutes before giving it some gas, and the thing freaked and died and I had to do the process over.