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Weird idle

2K views 7 replies 7 participants last post by  Silversky545 
#1 ·
When I'm at idle, the car bounces between 800 and then down to 500 rpms. It almost soinds like the car is going to stall and then catches itself? Could this be result of bad/ old gas because it sat in garage over winter and i had to remove the battery to recharge it. I would start it up every other week during the winter and let it idle for a bit and never noticed it. There was a period of about a month of me never starting it when the battery died. About a week after I put the battery back in is when I took the car out and I noticed it started to idle weird.
 
#3 ·
Your car needs to relearn the idle, since the battery was disconnected, Do a search in the forums. If you can't find it I'm pretty sure the process is to get in the car with it in park- do a cold start, and let the car sit and idle til it gets to regular temperature. Then cut the AC on and let it idle for another 15 min, then cut AC off and drive for about an hour.
That's close anyway- but search "relearning idle" I'm pretty sure that's your problem

Chris Rose at AM knows everything there is to know about this, so you could always PM him too.
 
#4 ·
Thanks for the help. I've noticed that when I'm completely stopped, like at a light it seems to be fine, but when I'm slowing down and I push the clutch in to put it in neutral it goes down to around 500 rpm and bounces in between 500 and 800 rpms until I come to a complete stop.
 
#5 ·
eouellette18 said:
Thanks for the help. I've noticed that when I'm completely stopped, like at a light it seems to be fine, but when I'm slowing down and I push the clutch in to put it in neutral it goes down to around 500 rpm and bounces in between 500 and 800 rpms until I come to a complete stop.
This is happening to my 08 stang and its manual as well. Any luck with the relearning idle?
 
#6 ·
This will happen when the battery is disconnected, or you load a new tune etc. Every time I have made a change this happens. Takes a few days and corrects itself. I've tried the AC bit, drive this many miles, blah blah blah, it will fix itself in a week or less depending on how much driving you do.
 
#7 ·
Clean your throttle body. The reason the car has to relearn the idle is because over time the throttle body gets a build up on it. Your car is automatically adjusting for this add time goes on but when the battery is disconnected it loses the information needed to control the idle. You clean the throttle body with a 7 dollar can of tb cleaner and all will run smooth.
 
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