Weird RPM fluctuation and backfiring

[BIGGZ]

Just got this 2010 GT that already has a JLT CAI, MBRP axle-back exhaust, and the mid cat/s cut out and normal pipe welded in. Also came with a BAMA SCT tuner in which he only had a 93 "PERF" tune and a 93 "RACE" tune. The only tune that runs decent is the 93 perf, but what confused me is when i tried to return the car to stock tuning it started running terribly. Which doesn't really make sense to me because its not like the car has cams or anything crazy so I would assume the default ECU tune would do just fine. In any case on the tune that runs decent I've noticed the RPMs normally idle at 1000 but now at idle the car struggles to maintain a consistent idle, usually bouncing from 950 to 900 RPM every few seconds. The car also constantly backfires lightly, even under 2000 rpms im always hearing burbles. Changed spark plugs, haven't tried coils yet as they looked good when i changed the plugs. Didn't fix the issue so i took off the throttle body, cleaned it, cleaned the MAF sensor and put it all back on but the weird fluctuating idle remains. Currently thinking either vacuum lines or a tuning issue but wanted input here before spending too much more money on false fixes. I've also noticed rarely when pushing the clutch in on decel my lights will flicker like there losing power. Not sure if its relevant just wanted to include all details I could.

 

[StockishS197]

Just got this 2010 GT that already has a JLT CAI, MBRP axle-back exhaust, and the mid cat/s cut out and normal pipe welded in. Also came with a BAMA SCT tuner in which he only had a 93 "PERF" tune and a 93 "RACE" tune. The only tune that runs decent is the 93 perf, but what confused me is when i tried to return the car to stock tuning it started running terribly. Which doesn't really make sense to me because its not like the car has cams or anything crazy so I would assume the default ECU tune would do just fine. In any case on the tune that runs decent I've noticed the RPMs normally idle at 1000 but now at idle the car struggles to maintain a consistent idle, usually bouncing from 950 to 900 RPM every few seconds. The car also constantly backfires lightly, even under 2000 rpms im always hearing burbles. Changed spark plugs, haven't tried coils yet as they looked good when i changed the plugs. Didn't fix the issue so i took off the throttle body, cleaned it, cleaned the MAF sensor and put it all back on but the weird fluctuating idle remains. Currently thinking either vacuum lines or a tuning issue but wanted input here before spending too much more money on false fixes. I've also noticed rarely when pushing the clutch in on decel my lights will flicker like there losing power. Not sure if its relevant just wanted to include all details I could.

Hi and welcome!

You cannot run the JLT CAI on the stock tune. The MAF housing is far larger than stock and a tune is needed to account for it via the MAF transfer function.

My recommendation is ditch the canned BAMA tune and switch to a good remote tuner of your choice (Lito is usually the best for 3vs).

 

[Blue03Cobra]

Hi and welcome!

You cannot run the JLT CAI on the stock tune. The MAF housing is far larger than stock and a tune is needed to account for it via the MAF transfer function.

My recommendation is ditch the canned BAMA tune and switch to a good remote tuner of your choice (Lito is usually the best for 3vs).

^-----This is the way. Lito is recognized as the absolute best, but I've also gotten great results with 5 Star, if you want something more corporate/mainstream.

 

[86GT351]

General rule of thumb to live with. If you change anything to increase air flow or fuel A tune is needed! Please also go to the new member thread and introduce yourself!

 

[GriffX]

The Bama perf and Race tunes are very old and not good. The Bama V2 tunes are far better maybe you can figure out if the last owner was enlisted in the free tune program and get new tunes from them.
BTW, what does "best tunes" means? Pedal feel? Power? Shifting? Clutch behavior? Show me the evidence
The driver demand map of my stock "tune" from my Audi is awful, it's a torture for passengers.

 

[BIGGZ]

Hi and welcome!

You cannot run the JLT CAI on the stock tune. The MAF housing is far larger than stock and a tune is needed to account for it via the MAF transfer function.

My recommendation is ditch the canned BAMA tune and switch to a good remote tuner of your choice (Lito is usually the best for 3vs).

Yeah the tune is at the very least not helping at all. At this point I think its just running slightly worse than it could do to the tune and listening to it after owning multiple well tuned cars it just makes me uncomfortable. Although since my previous car was a N54 BMW 335i I've also just gotten into the mindset of constantly overestimating issues to avoid catastrophic stuff catching me off guard. Any specific email or thread to contact Lito through? And are his prices lower/comparable to dyno tune prices? Thanks for the advice!

 

[BIGGZ]

The Bama perf and Race tunes are very old and not good. The Bama V2 tunes are far better maybe you can figure out if the last owner was enlisted in the free tune program and get new tunes from them.
BTW, what does "best tunes" means? Pedal feel? Power? Shifting? Clutch behavior? Show me the evidence
The driver demand map of my stock "tune" from my Audi is awful, it's a torture for passengers.

Pretty sure he was enlisted in the free tune program since he bought everything that he bought for the car from American Muscle and they offer it on the tuners free im pretty sure. The owner is annoying to contact however so hopefully BAMAs customer support is decent because if there are better tunes I can have until I get the money together to hit up Lito I'd be be willing to get it done.

"best tune" was in reference to its the only tune on the SCT tuner I trust. "stock" tune didn't run because as @StockishS197 said my CAIs MAF is different than stock. And the 93 "race" tune I dont trust at all considering BAMAs tuning reputation already.