Just noticed that the car is idling rough when AC is on, its pretty noticable- there is no check engine light or anything. Just rough idle- like vibrating...

The AC works just fine, the car runs just fine, there are no lights- so not sure what it could be.

I just picked up the car after getting Center GT3 style exhaust installed, not sure if that could have something to do with it.

Any input from anyone?

 

dirty MAF/throttle body

 

A/C compressor bearing going, dragging the serpentine belt?

 

Keep the suggestions coming guys, thanks! obviously i need to take it in and have a mechanic look at it

 

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cheap fix if it works,,takes 30 min. bottle of cleaner,,if not take to mechanic

 

OP... what engine maintenance have you performed? plugs/coils replaced?


serp belt? On another thread, I commented on a 07 car I was working on, and a small pebble had stuck onto the belt and sheared off and melted onto the WP pulley. iirc, your car is a tad higher miles.


Have you tried turning your compressor on and off while at idle/driving?


the vibration.... is it felt in the pedals, gear shift,steering wheel,etc?


your symptoms point to a pulley bearing as another poster suggested.


Try taking off your serp belt and check out your pulleys...wiggle for play, spin,etc.


Report back.

 

i have not changed the coils and plugs- a couple of times since this started, when i would turn the AC off to check the sound, i would hear a CLICK in the back but not always.

i will check that stuff and of course report back , Thanks

 

Well guys, it turned out it had to do with my center exhaust that i had just installed- it must not have been put on correctly by the shop that installed it, because i sold that setup today & went back to my beloved Fister D mufflers & the idle went away.

 

Pretty interesting that it affected the idle. I am still wondering why it caused the issue.

 

i think maybe it was just too heavy or not installed correctly, so when idle changed when AC is on, it shook or something. I hated that center exhaust anyways- had it 3 days and ended up selling my GT3 rear & center exhaust, now i have my FISTER D exhaust back on and i feel like i got my 911 back lol

 

Thanks for the feedback.

AC normally raises RPM by about 100 revs and feels like lost of 100 hp.

 

It makes sense that pumping all of the exhaust through a single center pipe would produce a lot more back pressure than having it flow through two pipes. Going with the center pipe also changes the length of the exhaust flow. I'm no mechanic, but these factors likely caused the rough idle. I wonder if this is a common problem with GT3 exhaust conversions.

 

In most cases, center exhaust are just "centered" as opposed to being on the left and right. Centered pipes are still the same 2 pipes closer/joined together. The amount of air exhaust would still be the same.

 

That makes sense. I guess the length wouldn't change quite that much, either.

 

I believe the Center exhaust would cause gases to flow differently than what the car was designed for- the thing just made the car feel "heavy" i didn't like it at all.

Now when i drive i feel that i'm driving & loving the drive & the sound of the Fisters, with that center exhaust i just couldn't stand the sound