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Pete, Technician
Category: Car
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Experience:  17 years automotive training and experience.
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Mitsubishi Lancer ES: I have a 2004 Lancer ES Wagon. Last night

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I have a 2004 Lancer ES Wagon. Last night I replaced the stock cd receiver with a 3rd party one. While the negative of the battery was unplugged, a friend cleaned off some corrosion form the terminals. When I plugged it all back up, it all seemed to work fine.
When I turned the car on thought it revved up to about 4k rpm and then back down to normal. But as I was driving and stopping at lights with my foot off the pedal, the revs where fluctuating between 1000 and approx 400 rpm. A second set of lights the engine actually turned off. I've had a look at my wiring and deduced that I have everything plugged in right and tightly sealed so no shorting is happening. I've also checked the battery terminal connections and they are clean and tight.
It seems to be getting worse though, as I start the car the engine idle fluctuates a few times until it finds the right idle speed. It'll stay good for a minute or so and then just turn off.
I'm assuming it's something to do with the work I did the previous night but it all looks good to me.

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Customer: replied 3 years ago.

Hi there. Yes I still need help with this.

On some vehicles the engine computer learns the idle position and on some when the battery is disconnected it no longer knows this setting with the idle.This sounds like an idle learn issue here with the computer fluctuating the idle control to try and level out but doesn't know the setting and in some cases this may even cause a stall out.I would contact a local shop with experience with these vehicles or a dealer to see if there is some kind of manual idle learn procedure.In some cases a shop or dealer may have to relearn the idle with their computer and or scan tool.

I hope this info has helped in some way,thanks Pete.
Customer: replied 3 years ago.

Thanks for the response. I believe you are right with the idle speed learning. I came to the same conclusion eventually. I tried some recommendations such as just starting the car and letting it idle until it reaches operating temperature then turning it off, then turning it on again for about 10 minutes and that should do it.

I did do that though and I must say it has helped a bit. It idles almost fine now albeit a few hundred rpms slower than before. It still fluctuates but it's only when the aircon is running. So when I slow down for a red light I have to turn the A/C off temporarily.


I may try to disconnect the battery and reconnect then try the idling thing but with the aircon on. The ECU might compensate better for it that way. But somehow I think the engineers at Mitsubishi would have thought about that and mentioned it the manual.

Your welcome.This does sound like a problem with the idle learn and if there is no manual relearn for the idle then a shop or dealer may have to do this with their computer or scan tool plugged into your vehicle.

I hope this has helped.Let me know if you need anything else,don't forget to rate my help here,3 to 5 is appreciated.Thanks Pete.
Pete, Technician
Category: Car
Satisfied Customers: 24207
Experience: 17 years automotive training and experience.
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