LenXIII

Hey Guys,

Have a 2012 GT M6 that I recently purchased. During the test drive it drove very well but within a day or two after purchasing I started notice a lack of power most of the time (not all the time) and some slight stuttering. After reading I feel the stuttering I feel is what a lot of people get when recently starting the car that is related to the drive by wire...The car idles smooth and sounds fairly quiet so I don't think I have a spark issue.

The car has a JLT CAI and gt 500 exhaust. It has been tuned so a tune issue could also be the problem. The issues I am having are the car just feels sluggish MOST of the time. Sometimes the car randomly feels like driving like a bat out of hell but most of the time I feel like the car is trying way too hard to move and it's just losing power somewhere. It's hard to narrow down. If it was the tune wouldn't it be more of an all the time problem? To give an example sometimes just driving it normal it's pretty easily to break the back end lose, especially during a turn under only moderate acceleration. When it's not running the way I think it should I have to give it WOT and it only slightly breaks the tires free after hitting that 5k+ rpm mark. When it's running right pretty much flooring it in first gear instantly let's the tires loose. I realize this isn't the best way to judge but I feel like it's over 100 HP less when it's not running right and the engine just feels like it's trying too hard and I can feel a little more vibration in the car than usual.

One last thing. Mostly when the car isn't running great but probably most of the time in general I get a fairly aweful smell during heavy acceleration. My car does have a cat but from what I read a lot of people have this issue even when their cars were new. I don't know if this is again relating to the tune or air fuel ration but the smell seems worse when the car isn't running to its peak. It also is hard to explain the smell...its not fuel or oil...if it's exhaust it's a very strange exhaust odor...I really cant explain how it smells.

Any ideas? I'm almost thinking of finding a stock intake and returning the tune to stock and try that...the car came this way so I have no tuner or factory intake. The tune appears (based on a local dyno shop) to be a custom tune and not a mail in tune. Also the car dynod 408 to the wheels when it was running good...right now it feels like 300 to the crank tops.

Derf00

Did you fill up before you started having the issue?

What octane of fuel are you using, what octane is the tune for?

LenXIII

I don't think the issues started after a fillup but I could be wrong. No idea what it was tuned for...I bought it off a car lot that told me it was stock... I've been using only 93 just in case it was tuned for that. I assume using 93 shouldn't cause the problems even if it was tuned for something lower right?

JimC

Did you get a tuner with the car? Or are you just assuming that there is a tune on it?

The JLT cai will require a tune so it could be it is on the stock tune and the previous owner didn't have the stock intake to put back on. If that is the case that could be the cause of your issues, and you should see a code or two come up.

LenXIII

It didn't come with a tuner. I think the lot tried to hide the fact the car was modified. I took it to a local performance shop that looked at it on a dyno and he told me it was definitely tuned by someone that knew what they were doing. He said he could tell by looking at certain values that were entered in that normal mail order tunes skip so he said it "appears" to have been custom tuned.

I just have to find a place locally that can take a better look...wasn't happy with that shop because other than telling me it was tuned they were basically useless. I just don't know where to start other than reverting back to stop intake and stock tune (which would require I purchase the tuner) and go from there. Maybe a tune up but I don't feel like the car is missing. I almost feel like it might be running lean but that's just a wild guess. I'll figure it all out in time I assume.

Dino Dino Bambino

Plugged up cats perhaps?

JimC

Since you don't have the tuner going back to stock will require a visit to the dealer for a reflash. If you buy a tuner now you can add your own tune, but the "stock" tune it will recognize is what is on the car now. Without the original tuner you can't put the car back to stock because you don't have anything with those values on it.

Menace

I'm guessing it's a fuel pump issue.

Buck Sergeant

All of these suggestions are worth looking into. I would first start by having my injectors power flushed. Not from a bottle, but a real deal power flush.

Derf00

If the car was tuned, the mods were probably removed but the car's tune wasn't. This would feel like it was down on power because your air/fuel maps are based on the mods (probably burning really rich now). Depending on how heavy those mods were, you can disconnect the battery for a little and reconnect it to force the car back to default/baseline values. This will temporarily 'hide' some potential changes that would affect driveability (like the sluggish feeling) until the car starts to relearn the fuel maps for the tune that's in it.

And +1 for going to the dealer for a stock reflash. A dyno shop won't have stock tunes just laying around to get you back to square one. Only the dealer or the tuner that's locked to the car. (or maybe the original shop that did the tuning if you can find out who it was.)