Fluctuating Idle

btowse · 05-08-2008, 07:06 PM

I have an 06 GT 5-speed with JLT CAI and 93 Octane Brenspeed tune. The car runs great, but when idling at a stop it drops from 1500 rpm down to 500 like it's going to stall and then shoots back up again. It'll do it 3 or 4 times before it smoothes out. It seems to do it even worse on damp rainy days. Anyone else have this problem? Maybe the MAF sensor on the CAI?

Gr8T STANG · 05-08-2008, 09:10 PM

Have you checked for any air leaks in the intake?
If nothing is physicaly wrong I'd talk to Brenspeed about it. It could be something in the tune.

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ski · 05-09-2008, 01:00 PM

Did the problem start immediately after installing the CAI & tune, or later on?

btowse · 05-12-2008, 05:38 AM

I haven't checked anything yet. I was going to see what kind of responses I got here first. I've had the intake and tune installed about 3 months now and it has just gotten worse lately. I did notice that it is worse when I have the defroster on too.

08SmokedAlloy · 05-12-2008, 10:09 AM

I had the same issue, it would drop then bounce up and and down a few times.. also whenI would sit for a while at idle it would move between 800 and 1000 rpms constantly likethe needlehad a case of the shakes. Nothing severe, but noticable if you look at the gauge. I have a c&l racer and a gt500 tb,I think there may have been a leak near the tb. I never received the right hardwarebecause of the twin 65mm tb, and the clamps the intake came with didn't fit soI "engineered" it temporarily.. I just fixed thatissueon friday with some serious hardware and the problem seems to have gone away.I would definitely check for leaks as the primary problem.

rugedraw · 05-12-2008, 11:23 AM

Yea, check for leaks. Simple installs get taken for granted, but a small leak can throw the entire system off.

It could also be the tune. Tunes are a long, complicated seuquence of codes and if one is off, it could throw the car off. Those custom tunes are great, but they have to be perfect. I would try putting the stock tune back in, and re-installing the tune (after checking for leaks and tightening everything up). That will re-set the computer, and if there were any leaks, it can re-train itself.

Since you paid for a BrenSpeed tune, I'd call them up and make it their problem.

btowse · 05-12-2008, 07:41 PM

Thanks for the advice. I was going to change the tune to the 89 octane anyway, so I'll check for leaks first and then change the tune and let you know if that does anything.

B.T.W. l love the GT500 front end rugedraw!

btowse · 05-19-2008, 06:59 PM

Checked for air leaks. Everything seemed to be tight. Changed the tune back to the 87 octane tune. No difference in idle fluctuation. E-mailed Brenspeed for advice on the subject, and they told me to check for air leaks. I must be missing something.

rugedraw · 05-19-2008, 07:21 PM

Weird.....my car started doing that after I installed my headers two weekends ago. After a few days, the car seemed to train itself to deal with it and it runs just fine now.

If it started acting that way after doing any particular mod, I suggest you trace it back to that. You said it's been getting worse; worse since you installed the CAI & tune? Check for hair-line cracks in the tuning or rubber pieces of the CAI. Maybe a tear in the actual filter. If those pieces are intact, I'd ask BrenSpeed to send you some new tunes. It has to be that.......

kcmarti · 05-20-2008, 04:57 AM

BTOWSE, this is a common problem with CAI (or any "oiled" air filter) and tunes. Just clean your throttle body and MAF (do not touch the wire just spray it) and the issue will go away. My car did this the first time after a header install on the stock tune, which went away by itself after a couple of days (like RUGEDRAW) and also after installing the a Predator and BamaChips tune. I wrote Doug at BamaChips about this issue and the response I give above is what he told me. Cleared up my issue right away and quite a few others here on this forum. Hope it helps you.