Erratic Idle

[brady_f]

Took a short video this morning showing a little bit of the fluctuating idle. It starts to do it a little worse after the car has been driven for a while but you can vaguely see right around the :11 second mark what I am talking about. Fluctuations anywhere from 50-250 rpms it looks like. Checked for leaks around intake and MAF and everything looks okay. Any ideas?

Mods are:
JLT CAI
BBR Tune
Lethal O/R X
Flowmaster Hushpower Axleback

http://s296.photobucket.com/albums/mm171/bfedro427/?action=view&current=VIDEO0005.mp4

Even if the video is no help at all what could cause the idle to this? Obviously I was thinking vacuum leak or maybe air bypassing the MAF...

 

[erod550]

My car (2011 GT) does this bone stock. Pretty common I think.

 

[brady_f]

My car (2011 GT) does this bone stock. Pretty common I think.

 

[Full_Tilt]

Thats just how it is with a performance engine.

These engines have a little lope even when stock, when you start doing exhaust and intake mods its most likely going to de-stabilize idle even further.

If it bothers you you could get the a tuner to richen up the idle a little bit and you should be able to make it a little smoother, but at the cost of burning even more fuel when idling.

 

[brady_f]

The lope and overlap from the cam doesn't cause the rpm guage to dance around like that does it? Atleast it didn't in my H/C/I LS1 that had a fairly large cam on a 110LSA; idled perfect. I know its an entirely different engine so I'm comparing apples to oranges, it just doesn't seem right sometimes. As long as everything is okay mechanically then I am not going to worry

 

[G.T]

i'd start by disconnecting the battery for 10 minutes (or reloading the tune) and cleaning the throttlebody... then crank the car and let it idle on its own for a minute or so.
this should reset the idle trim and force the PCM to relearn it.. usually helps with most similar idle issues, especially if the TB was dirty and the PCM was reset for any reason

 

[cdog1157]

My car (2011 GT) does this bone stock. Pretty common I think.

Mine did it stock as well, and still does occassionally with a Bama 93 race tune

 

[KJGT]

Mine did it pretty bad with the initial Bama tune, I called and told them and they sent me revised tunes that fixed it. I didnt notice anything stock but it wasnt stock for that long..

 

[Whocares05050]

Can you please explain to me in what way you feel you have an "erratic idle"? Go sit in any new vehicle. They all do it. Erratic idle and i was expecting the RPM's to fluctuate from 500 RPM to 1200 RPM. What you are seeing is a NORMAL condition, with or without a tune or mods on this vehicle. Do you honestly think a(ny) vehicle has a perfect 800RPM idle speed and that absolutley nothing can change it? Did you even notice that when your fans kick on it will drop in RPM around 650 then back up? Because its drawing from the motor. By the titel thread you made it seem as if one of the cylinders droped. Drive the car, and stop looking for little things like this. Normal operation of this motor.

 

[SlowA$$5.0]

Did you rev it or are you saying that's what the problem is?

 

[Rob72]

These engines has a normal amount of misfire stock according to Brenspeed at idle. Add a tune with the timing bumped up as much as possible and that is going to increase somewhat. Once the VCT kicks in everything will usually smooth out. Not all strategies can handle the most aggressive timing[mine(VXT3)] so you might want to have them send you another tune with less advancement.

 

[KJGT]

LOL, I didnt even watch the video, when I put the first tune it it would hunt from 300-1100rpm and wouldnt stop. Even died a few times, I ASSumed thats what the OP was talking about.

From what I see on the vid it looks perfectly normal.

 

[Rob72]

Similar story here. I got a code and a backfire if it didn't stall first.

 

[scotty2hottie]

once you tune them or disconnect the battery, you need to relearn idle.

let the car warm up and idle for about 5 mins, the max a/c on fulll blast for 2 mins idling then drive around for 10 mins city driving with a/c still on full blast. that has been what im doing. seems to get it alot closer. It isnt nearly as rough at idle once you do that. After cai, o/f xpipe, tune, and cat back mine would actually died at stop lights on the regular until AM put this out and i did it. It will still fluctuate alittle thats normal but not nearly as bad.

goodluck

 

[GrabberBooGT]

I'm as picky as anybody, and that idle is normal, IMHO. Every car I've ever had has done that. I'm told the computer is searching a gazillion times per second for the perfect timing, air/fuel ratio, etc.

When it was revved up, it would make sense that it took a second for the computer to adjust the timing, VCT, etc -- thus the even more "erratic" idling for a couple seconds.

 

[JDM74]

You would lose your mind if you hooked a MSD dash hawk to it or something that would give you actual numbers for your RPM, lol. Stop worrying, it idles better than mine!

 

[HossWhisperer65]

once you tune them or disconnect the battery, you need to relearn idle.

let the car warm up and idle for about 5 mins, the max a/c on fulll blast for 2 mins idling then drive around for 10 mins city driving with a/c still on full blast. that has been what im doing. seems to get it alot closer. It isnt nearly as rough at idle once you do that. After cai, o/f xpipe, tune, and cat back mine would actually died at stop lights on the regular until AM put this out and i did it. It will still fluctuate alittle thats normal but not nearly as bad.

goodluck

I tried this exact procedure and it substantially improved my idle quality and off-idle throttle response.

 

[RedMustang]

Nice stance.

What's done to the susp. ?

 

[Ducky]

My car (2011 GT) does this bone stock. Pretty common I think.

As does mine. That does not qualify as erratic by any stretch.

 

[Konablue10Gt]

Mine and some of my customer cars have had this issue too. One of the easiest ways to calm it is raising the idle from 650rpm to 850 rpm.

I hope this helps.

Adam