[HarryNW]

I purchased my 2013 2SS/RS 7 weeks ago at the Bill Pierre dealership on Lake City Way in Seattle, WA. I almost immediately felt like the idle was a little rough and there was some obvious hesitation and bucking at low RPM, especially on a cold start.

Being my first real muscle car, I thought this might be normal. I proceeded with a few trivial mods: F8 Fuse Pull for Dual-mode exhaust, C.A.I. CAI, Skip-Shift Eliminator and the Octane Fuel Correction. I also checked my MAF for "weak/strong" and (a week after the CAI install) thoroughly cleaned the MAF with MAF cleaner.

Still, I continued to have rough idle, hesitation and bucking in lower-rpm, especially in the morning.

I called the service manager at the dealership about it and he said to definitely bring it in. We agreed the best plan was to drop off the prior night to allow the service team to see how it looked on a cold start, so last night I dropped it off. I told him to be sure they test-drove it, as the rough idle was subtle, but the hesitation/bucking was completely obvious in a test drive.

This morning by 10am, the service manager called me to say that there were no engine codes (we already knew/discussed that previously) and that they "could not properly test the car until it has the after-market CAI removed". I asked if they even test drove it and he said no. I insisted that the CAI would not cause this type of behavior and re-iterated the importance of test driving. He said there was nothing more they will do to test/troubleshoot the car until I remove the CAI, but would ask someone to test drive it.

As this was my first visit to the service department, and because I am new to most of this, I did not want to burn any bridges and agreed to come pick up the car and schedule a new drop-off for this Sunday night, giving me time to put the stock air filter back on.

However, by the time I got to the dealer to pick up the car, I had digested how much effort it will take to swap out the CAI and frankly felt pissed that I would go through this effort only to prove to him that this is not a CAI issue. He mentioned that they took a short test drive and did not notice any bucking.

I later had by brother-in-law (big-time motorhead, big mustang customizer) drive the car and he immediately noticed the idle and hesitation. He was actually able to show me that even at higher RPM, if I simply kept a stable RPM at 3,000, the engine was missing/hesitation rather than maintaining a consistent run. He said that if the dealer was not willing to put it on the computer, that a local speed shop could probably tell me exactly what was wrong in an hour or less, without actually applying a tune, but it would run a few hundred bucks.

My current plan is to put the stock air filter back on, replace the F8 fuse, take it back to the dealer, and see what they say.

Any thoughts/feedback?

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Update: July 16th - Bottom Line: Move the Window Fluid Reservoir

Per the thread history, I had finally identified that there was something about the CAI install that caused the hesitation/bucking - I replaced the stock AF and the issue disappeared. Tonight, I re-installed the CAI. As I did so, I was staring at the C.A.I. heat-shield-box and I am thinking - where is the airflow? The stock AF has major open routes from beneath the engine and to the sides of the AF arm. When contained in the CAI box, the fluid reservoir consumes nearly every inch of open area beneath the CAI filter.

So I decide to leave the CAI plexi-glass cover off the box (it leaves a scant 2 inches of clearance to the underside of the hood), close the hood, and go for a little drive. Bingo, no more hesitation/bucking. I return, re-add the cover, and test drive - noticeable hesitations, especially in the 2000-3000 RPM range under modest acceleration. I return, remove it again, test drive again, no hesitation in acceleration.

Just ordered the relocation kit for the fluid reservoir, but will keep the CAI cover off until then.

Next, I installed the VMAX Ported Throttle Body. I can see why people have been excited about this - obviously you cannot sense the few HP gain, but the VMAX PTB clearly provides an improvement to throttle response. It now leaps out when I punch it.

My bottom line: I should have read more about various brands of CAI and their recommended installation tips - even though C.A.I. does not specifically call out the relocation of the fluid reservoir, it should be highly recommended up front. There are some other posts here that recommend doing this, and even go so far as to say that adding this type of "boxed" CAI without relocating the reservoir is a step backwards. I can now wholeheartedly agree.