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#1: 01-26-2009, 11:32 AM
Pulsing Hesitation at Constant Throttle
jtmvt's Avatar
Title: Senior Member
Location: Jericho, VT
Car: 2005 GT Ltd MT, Dominator 2.5R w/ FMIC
Posts: 226
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I have something strange and very annoying going on with my car. A little background info. first - I have a 2005 LGT MT Limited w/ aftermarket turbo (Dom 2.5R), all necessary supporing fuel mods, FMIC, Cobb Intake, and of course a full catback aftermarket exhaust. The car was dyno tuned Dec. 18th, 2008 on a Mustang Dyno using a Cobb AP V1.

A couple of weeks ago, I started noticing that my car was experiencing pulses of hesitation or back pressure at constant throttle. It doesn't seem to matter what RPM or what gear I'm in, when I have my throttle depressed at a constant pressure, I notice this hesistation or stutter, kind of like engine braking...When this happens my AFRs jump up like my car is running too lean for these brief and repeated pulses. It's becoming very annoying.

I've had my mechanic look over my car thoroughly, and he did find that my Perrin EL Headers were leaking some, so he fixed them. He checked for any other possible exhaust or vacuum (boost) leaks...none to be found. Even after the header leak was fixed, I still notice the problem, almost more prevelant but hard to say for sure. The only thing we can think of is that it must be something to do with the tune. I'm waiting for a little bit warmer weather to log my tuner some data from my car to see if he can smooth this out. I find it odd that I didn't notice this right after the tune, and it wasn't until just about two weeks ago that I started to notice these symptoms. No doubt the header leak was there during the tune, but even with this fixed, it doesn't seem to make a difference.

Anybody have an experience with a similar symptom to this or have any idea what could be causing it? I'd appreciate any input members may have......

Last edited by jtmvt; 01-26-2009 at 06:31 PM..
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