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Surging And Stalling


08SGT1188

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I recently purchased a 2009 GT500 with 6,000 miles on it. It has a K&N cai and a custom tune done at mustang week in Myrtle Beach. It just started to surge at a constant speed and sometimes when you push in the clutch it stalls. The surge is not bad but noticeable to me. Any one had this problem or know what might be the cause?

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+1 on the tune. Not sure, but I remember reading bad, bad things about the K&N back when I was doing the CAI research for my car. Maybe call Justin at VMP and ask about it. I ended up getting one from him with a JLT, along with about a million other owners. No problems whatsoever for a few years now with the intake and tune.

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Could be one of a few things:

 

1. Are you sure it has a custom tune on it? Early in the life of the GT500 cars (07-09 timeframe) K&N was selling and advertising their CAI's as not requiring a tune. Justin @ VMP and many other tuners proved this to be false, with dyno sheets and tuning logs to back up their findings. The only reason it "worked" (sometimes) is because the car eventually went into failsafe mode and was able to run (though not very well). Some were able to get by with it, while others had issues with surging, stalling, and check engine lights. I guess the results depended on the area of the country they were in and the conditions at the time. Bottom line - the most reputable tuners in the community have proven the K&N intake does require a retune (as does any other intake that changes the MAF housing size). If properly tuned however, it's a perfectly fine CAI.

 

2. If it does have a custom tune the next question is, is the tune properly calibrated for the current setup? The only surefire way to find that out is to get it on a dyno with a reputable tuner and have them check it out. If you have a relatively simple and common setup you can also purchase a mail order tune from one of the many tuners out there and it will likely work just fine.

 

3. If you can rule those out, then you want to start checking for problems that others mentioned - bad fuel filter, dirty MAF sensor, loose hoses and fittings, etc. Justin @ VMP has said many times that most of the issues like these they see are due to problems with loose connections or improperly torqued bolts on the intake tract causing vacuum leaks.

 

Good luck!

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