Hey first time posting here, and only moderatly knowlegable with cars, so please bare with me. I have a 2002 lancer es with 87k miles, automatic, with no mods, everything is stock, and here is my situation..

So today I installed an after-market stereo, and had no problems what so ever with that. I disconnected the negative cable from the batter, installed the stereo, connected everything and then reconnected the battery. Everything worked fine. However, I then took my car out for a drive, and noticed that now when i am sitting at a light, my car idles below the 1k rpm. tpically its around 800 rpm and periodicaly drops to about 400 rpm and shakes pretty bad. I know on previous cars i have had i just adjust the idler arm and its fine, but looking at it on my lancer, it seems its a colt i would have to tighten from what i can tell. is this what i should be doing? or is it possible something else happened? only thing i can think of is if the computer controls the idling rpm and it somehow got reset. Oh, and also, since doing this, the rpm's jump right before shifting into 3rd gear. they jump up to 6k rpm or so. any help or suggestions would be greatly appreciated.

 

If you disconnect and reconnect the battery the cars ecu resets trying to figure out what is the best rpm to idle at and gets the best fuel economy and what not. If you disconnect the car for anything let it sit for around 10 to 15 and then drive it a little, it will go away after about a half hour of running time. That happened to me when I installed my subs and my car shut off at a light and scared the **** out of me. Now it's fine after talking to another member. So just do that and you should be good.

 

+1 Exactly as lance a lot stated everytime you unhook the battery you gotta let it sit at idle so it can relearn everything. Matter of fact I have to do mine too. Last time I unhooked the batt I just took off afterwards and I think my gas mileage is hurting since I didnt give it a chance to learn

 

thank you all for your help. i re-re disconnected the battery, then let it idle for about 15minutes, it was a little rough still for about a week then it lately seems to be working like new..

 

You got to give it time, it's a good little car, just needs to be taught like kids, dogs....woman.