I recently starting having a problem with my RPM Idle and was wondering if anyone else has shared the same problem and has any info. It usually happens when I am slowing down and I put the car in neutral the rpms will go down and then start jumping around under and over 1k without applying the gas pedal at all. At high speeds slowing down quickly with make the Rpms drop so low the car will shut off. The only real motor mod is a tune and intake by brenspeed running a 91 octane tune with exhaust work.

 

If you recently reinstalled the tune or disconnected the battery, then drive around for 20 miles or so, and see if that clears things up.
If it still happens, then there's a procedure in the battery maintenance section of the owner's manual that addresses an erratic idle.

If you did not reinstall the tune or disconnect the battery, then make sure all of the air intake connections are secure.
If they're ok, then clean the MAF sensor and TB.
If no luck, then either the TPS or TB may be bad.

 

The Battery was discounted when it was back in the bodyshop a few weeks ago but it has been driven well over 20 miles and is still doing it

 

You should be asking Brenspeed. It's a tuning issue.

 

This happens to me also. When i am slowing down for a red light and i put it in nutural the RPMs will jump around with out me applying any gas.

 

Glad its not just mine but now makes me more curious as to what it is. You do have the same brenspeed tune

 

I believe some people have fixed this by cleaning their throttle body and/or the MAF sensor. Could be worth a shot...

 

A friend of mine has a 06 gt with about 60,000 miles on it and it is bone stock and he was also telling me his car is doing the same thing when slowing down. My car is a 08 gt and only has 17000 miles on it hope it is nothing bad.

How should i go about cleaning it? I thought you were not really exsposted to touch the MAF sensor,

 

Oh, boy. I had a feeling that questions was coming I personally have NOT done this before, so please take my advice at your own risk. I believe there is such a thing as "MAF Cleaner" that you can use (obviously) on the MAF. Likewise, I believe that there is a throttle body cleaner for cleaning the throttle boy. You're best bet is to wait for someone else to chime in here and/or search around the forums; I know it's been mentioned several times before.

 

The same thing happened to me 3 months ago....my buddy told me to check my spark plugs and there was the problem. 4 of the 8 were completely out. I changed them and its been running like normal now.