Custom Tune Gremlins!!

[psyco]

OK, on my 06 GT (auto) I have a C&L Racer CAI and am running a Brenspeed 93 octane tune. Been running this setup for about a month now. It seems as though my performance has gotten a little sluggish and lost some pep since I first installed the tune. Additionally, My trans feels as though it's shifting in odd ways. Its somewhat hard to explain. For example, at ~50-60 mph I get this little dip in power (rpm's and acceleration) immediately following the shift from 3-4 (not at WOT) as though I have an instant of heavy drag on the motor. Also, it sometimes feels as though the trani is shifting too soon and it almost skips 3rd gear altogether. The shifting issues don't seem to happen at WOT however, although overall performance seems a little diminished. My mpg's have also dropped about 3-4 mpg at highway cruising speed (70 mph). I did clean the MAF thinking that may be the issue, but it didn't help. I should mention that I often turn OD off when driving around town as well as always turn off the traction control. Any thoughts would be greatly appreciated.

 

[NastyStang113]

Contact Brenspeed .. Give them a chance to fix it.

 

[o0Dan0o]

The MPG is an obvious sign that something is amiss. Call brenspeed, but I would also try resetting the ECU.
Dan

 

[psyco]

I did try resetting the ECU. Unfortunately it didn't help. Shot off an email to Brenspeed last night. I'll relay their suggestion(s) once I hear back from them.

 

[psyco]

Dave at Brenspeed got back to me and suggested I may have a dirty throttle body. He pointed out that tunes do not change over time. I'm inclined to agree, so this may not be a custom tune problem at all. He did not address my decrease in mpg or my power lag issue. I sent him a reply to see if he could offer some additional ideas. I doubt that the throttle body is the issue, but I will clean it after work and report back.

 

[NastyStang113]

Dave at Brenspeed got back to me and suggested I may have a dirty throttle body. He pointed out that tunes do not change over time. I'm inclined to agree, so this may not be a custom tune problem at all. He did not address my decrease in mpg or my power lag issue. I sent him a reply to see if he could offer some additional ideas. I doubt that the throttle body is the issue, but I will clean it after work and report back.

The tune that is written cannot change but the PCM does use adaptive learning to make changes to the tune. So in a sense the tune isn't changed but than in a sense it is changing. If you did reset the tune it'll clear all KAM data and the adaptive learning process will start all over. So, if your tune originally worked than there is no reason why it won't work now. It has to be something else. How many miles do you have on your car?

 

[o0Dan0o]

Check to see if your CMC plates are sticking, that could easily cause your issue. It could be a gunked up throttle body, but I find that less convincing. Both of those are easy to check, maybe an hour to clean both. Cleaning the CMC plates does require removing the intake, but that really is a breeze, and you can check to see if they're sticking by moving the linage behind the intake.
Dan

 

[sycd]

Try reloading the tune.

 

[psyco]

Yes I did try reloading the tune. No change. But I did get under my hood at lunch and spotted what may be an issue. It appears that the hose running from my C&L CAI (by the throttle body) to the valve cover is may be collapsed. Could this be my gremlin? I'm at work so I can't try that fix yet. When I installed the CAI I used the hose that came with the unit as the factory hose would not fit over the fitting off of the CAI.

 

[o0Dan0o]

That's just a PCV line, shouldn't make too much of a difference, though you never know what little change will drive the computer nuts.
Dan

 

[NastyStang113]

It very well could be causing a problem.

 

[psyco]

I want to thank you all for your suggestions. I fixed the hose problem, cleaned the MAF and TB, reset the ECU, reloaded the tune, checked for sticking plates, lit candles, threw salt over my shoulder, and prayed to the Stang Gods. No change at this point. I'm beginning to think I may have a trani problem. I'll post periodic updates as I continue my hunt for the gremlins.

 

[psyco]

Update!! Well, before returning the car to the stock tune and taking it to the dealership for a checkup I decided to try something. I tuned the car to the 91 octane performance tune while using 93 octane fuel (haven't found 91 in my area). My mpg's rose 4-5 gallons per, and all other symptoms (gremlins) seemed to fade as the car adapted. The trans is shifting as it should, the sluggish peddle is gone, as well as the strange power dip when accelerating at highway speeds. The difference is night and day. My question is could I have inadvertently done something to ruin the 93 octane tune (SCT Brenspeed)? I've emailed Dave and am waiting for his input. He's probably scratching his head too. Any thoughts out there?

 

[NastyStang113]

Sounds like the gas you thought was 91 octane was probably equivalent to a lesser octane.

 

[psyco]

I've been using Marathon 93 octane. Scary to think that Marathon's gas isn't quality gas. If this is true, could I be looking at possible engine damage as a result of the octane level be lower than it should be?