bk7794

So I accidentally left my lights on at work.. and I needed to get the car jumped. The car was idling fine before this all happened. So the idle seems like it is stuck on cold start mode, which is that the idle is higher to warm the car up...thats what I am going to call it..I would come to a light after the highway and the car would idle perfectly and then after driving around in town, in like a minute or two the idle is back to the high idle and the car is trying to keep it down but it just fluctuates...


So I have tried to remove the battery, jump the terminals to reset the ECU which have all worked before...but now I am stumped...my guess is that it has something to do with the coolant...it has nothing to do with my IACV being bad...its been replaced twice.

dsmchad

reset the ECU one more time,Start it up cold, do not touch the throttle and let it idle untill it is up to full temp and the fan comes on. sometimes when you kill the battery, jump it and take off driving the ECU takes itself a year to figure out the idle again. If that doesnt work im watching this thread because my car has done the same thing for over a year and i cant figure it out.

bk7794

Alright I will do it when it is cold this weekend...I have done it before once when it was hot...I reset the ECU like I would be timing the engine using a wire...still nothing this time...I really think its a coolant issue because I notice my gauge is a hair off..

fleabag

jumping a car is a bad idea, just because the people on jackass do it doesn't mean you should do it yourself.... As for the battery, take it to autozone and they'll charge it for free, put it back into the car and give it a day or so and it should be fine. Don't let the alternator try to charge a dead battery because you can burn out the alternator.

bk7794

Yeah...I never thought of doing that...but then again I never thought I would be an idiot and leave the lights on...

4drEF

Why is jumping a car once in a while a bad idea?
How is driving the car (sufficient air flow for cooling under the hood) allowing the alternator to burn up doing the job it was intended to do?

bk7794

I didn't think so either...however I wonder if I did something wrong while hooking up the jumper cables...I was told to just hook them to the + -...so I did it...I wonder if I fried the ECU...

4drEF

You hook + to + and the - on the good battery and then chassis ground as close as you can to the distributor on the dead battery car.
If you just did + and + then I can imagine there was a difference in potential greater than 12v since you didn't make the grounds common. Surprised your ECU fried without the fuse popping.

dsmchad

jumping is a car is perfectly fine to do, its no different than having your battery almost dead and bump starting it or it barely cranking enough to start and letting the alternator charge it, thats what its job is. if you only hooked + and + and no negative you dont have a complete circuit to jump it and nothing is going to happen at all. no offence but i can see some of you guys do not understand simple electronics and the original post is about the idle, not how to jump start a dead car.
as long as you didnt hook them up backwards theres not much wrong you can do. it didnt start smoking and catch on fire so you must have it right.

bk7794

The guys that I jumped it to has a degree in electronics...so I know he knows what he is talking about...I hooked it up + to + and - to -....regardless I am a bit worried about this problem.

bk7794

So today it did it, but only a few times...sometimes it fluctuates...then it kicks down.

fleabag

Did you take ANY advice from the users in this thread or did you just sit back and do nothing? How about you take my advice and get the damn battery charged. When you're done and if charging the battery resolves this problem, I can then explain to you my theory on why it worked.

bk7794

Many of the posts were just debating your post...

So anyways I was working on it last night and today.. I noticed that it is very intermittent, sometimes it idles perfectly and other times it doesn't...and the car idles great when the headlights are on. So I don't think it has anything to do with the alternator.

fleabag

They were just debating about jumping the car, not about charging the battery. What's done is done and frankly charging a dead battery with the alternator is a terrible idea because it wastes a huge amount of gasoline and can burn out the alternator. Regardless of any debate about how bad it is to charge with the alternator....

Get the damn battery charged at a place like autozone or even better, buy a battery charger yourself, charge the battery and then put it back into the car. Severely discharged batteries can cause a variety of problems with the car. 11.8V is considered fully discharged battery and 10.5v is the minimum to crank the engine over. Discharging batteries to a very low level will lead to sulphation of the battery plates which inhibits the available capacity of the battery.

dsmchad

lol if the car starts the battery IS charged. omg its no wonder i stay off forums usually. full of complete tards.

bk7794

I actually think the problem is almost solved...I hope. It didn't do the high/fluctuating idle at all on the way back from where I work...and I was doing a lot of intown driving, both with the lights and without the lights...I will keep posted on what happens.
Yes I hear that like 12.4 is a good battery with no problems...I am aware that discharging the battery is terrible for both the alternator and the battery...but the only reason I was ruling this out was because once when I cleaned the terminals it did the same exact thing.

I think I will invest in a battery charger, this is good information. Thanks.

fleabag

If you buy a battery charger, I recommend getting a 3 stage "smart charger" that has a desulfate function. I have a 3 stage battery charger but it does not have a desulfate function and because of that, I'm in the market to buy a battery charger. I've been looking at the batteryminder battery charger and while it's a bit pricey, the desulfate function is suppose to double the usable life of the battery. Either get a super cheap battery charger if you don't care too much about your battery or pay up and do it right the first time by getting a really good battery charger.

fleabag

Sorry, if anyone is a tard it's you. You obviously don't know a thing about how lead acid batteries work. A lead acid battery discharged below 11.8V will do severe damage to the battery yet a car can crank with a voltage as low as 10.5V. A lot of newer cars will suffer a lot of electrical problems and errors when their batteries get discharged below 11.9v. I've seen engine immobilizers and check engine codes cause by running a car on a very discharged battery. You're right, you should stay off these forums for the betterment of all who read them.

JDpower

If you unhooked the battery (reset your ecu) then your car is going to run like crap from anywhere 10-100 miles because the ecu has to readjust itself to get used to your driving habits all over again. Thats probably what happened and is no big deal.

bk7794

I will check my voltages...just to see what they are...hoping for over 12..
Okay so that does happen...great. Thanks soo much. Car seems to be running well now, so that is what I was thinking.

Mark L

unhook and rehook battery, doh I'm an idiot, thats the only thing I didn't do and now I'm just fine, thx guys