Livnlow

I apologize for the long post but want to provide as much info as I can in hopes of someone being able to help me out. I have a 6 sp 11' GT. I've had the JLT CAI and Bama tunes for at least 5 months now. I originally ran 87 tunes and then decided I wanted to get all the power I could, so I requested 93 tunes. At the same time, I had a Flowmaster cat-back installed. Ever since the new tunes and exhaust were added, I get a hesitation/jerking when accelerating (not even WOT). It is worse at cold starts and gradually improves as I drive. Working with Bama I've tried the idle relearn process twice, battery disconnected for 10 mins with high beam switch on, batt disconnected for 4 hours, switched stations where I purchase gas, removed and reinstalled the intake, and tried using 91 tunes. All this has managed to do is move the range I feel the hesitation from 2K-3K to now about 2500-4000. I'm really out of ideas and am willing to try almost anything short of an exorcism or voo doo witch doctor. Anyone?

waykooljr

Have you changed your fuel filter?

I had these same symptoms on my '06, I cleaned my throttle body first, which was an amazing improvement. Then changed the fuel filter and it got even better.

Livnlow

You think fuel filter with less than 8,000 miles on the car?

waykooljr

I don't think so but it is possible and the symptoms are in line with what I went through.

Car was running fine, changed the battery out and it started running poorly, surging, stalling and rough idle. Tried the relearning process several times, no go. Cleaned the throttle body and changed the fuel filter as recommended here at MF, it's running like a champ now.

Might be worth it to at least check the throttle body, I know mine was easy to remove, not sure about the 5.0.

pdonket

Just want to stop in and say that the 2011+ models don't have changeable fuel filters. They are in-tank and are maintenance free. So the problem likely lies elsewhere

CrzyHrs

I have the same issue in my '12. It first started when i put my axle back, CAI, and Bama tune on. I run a 93 tune all the time, never put 87 in it. Mine only does it with a cold start up though, once it gets up to temp it runs/idles fine. I would like to know why it does that though. If you find out anything else let me know. I may try some of the suggestions listed above.

waykooljr

Sorry LivnLow, I did not know this, thanks for the correction pdonket.

Just trying to help, I know how it feels when your baby isn't running well.

Enochius

I have the same problem on my 12 GT. My car is completely stock. It only does it before it warms up. Once the car hits normal operating temperature it doesn't do it at all.

allenmaty

Mine has 4K miles on it and it does it when cold, but only for the first min, sometimes I start in 2nd for the first couple of min to minimize the jerking, I really didn't think much of it until I saw your post.

AzPete

To the OP....try going back to the stock tune, run '93 for a tank+ and see how it is. If it is still there, than it is a stock car issue, if it is gone, it is a aftermarket tune issue. Then deal with the proper business to fix said issues.