Misfiring question

Discussion related to the 4G69 powered Lancer Rallairt
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25centguy
Posts: 11
Joined: Thu Feb 14, 2013 10:10 pm

Misfiring question

Post by 25centguy » Fri May 23, 2014 12:23 pm

My car has been having a rough idle on cold starts. When I start it the idle is at 1200 rpm and then its like the engine is misfiring because I can feel it shake and then the idle goes up to 1500rpm slowly idles down and then when it gets warm has a nice idle at around 750rpm. Someone said he was having the same problem and when putting back the stock ecu everything was ok. Any ideas?

hackish
Site Admin
Posts: 588
Joined: Wed Jan 05, 2011 1:49 pm

Re: Misfiring question

Post by hackish » Sun May 25, 2014 5:00 pm

Can you post a list of mods? In general I don't normally change the fuel or timing settings for the idle portion of the map.

-Michael

25centguy
Posts: 11
Joined: Thu Feb 14, 2013 10:10 pm

Re: Misfiring question

Post by 25centguy » Tue May 27, 2014 11:49 am

List of mods: not much

AEM CAI
Full exhaust with OBX header
RRM UDP

hackish
Site Admin
Posts: 588
Joined: Wed Jan 05, 2011 1:49 pm

Re: Misfiring question

Post by hackish » Tue May 27, 2014 10:46 pm

Should be no real effect there. It is possible that your MAF or primary O2 sensor is starting to die. After a flash is done it's normal to have a little bit of rough idling while the ECU re-learns the idle throttle positions.

-Michael

darewood
Posts: 18
Joined: Mon May 07, 2012 10:59 am

Re: Misfiring question

Post by darewood » Thu Jul 03, 2014 9:07 am

Exactly what Michael said, but the idle goes up also because of the operating temperature so low. If you have the editor and the tune you can see at what temperature corresponds to what rpm the car will idle at. Once the car is warm it will go to the standard 750 I think it is. I have mine set at 1,000 just because I have a stiffer motor mount haha, so I don't really remember what stock idle sits at.

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