Hey Everyone, I need some input on some problems I am having with my coupe. This is a semi long post as I'm trying to be as descriptive as possible but please read it all.

I purchased a used exhaust system that had minor scrapes on the flex pipes but I'm afraid that I have made them worse since I lowered the car. I know for a fact that I have scraped the flex pipes more then once and I'm figuring that is the reason that the problems are becoming more prominent.

Here are a list of problems that I am having and I just want to input on whether they are all directly related to me scraping my flex pipes open or if I'm running into multiple problems at once.

1) After pressing the gas pedal the car will cruise around 1200 RPM's while in first even when my foot isn't touching the pedal (At some points it feels like the car is out of control)

2) When I press the break pedal, the car while decelerate smoothly until about 1000-1200 RPM's and then the car will fell like it is trying to accelerate again, then suddenly the RPM's will drop to 550-600 and then the car will go back to idle at 650-700 RPM's.

3) When I'm at a stoplight the gas pedal will vibrate.

4) The air under the car will be very hot right by the flex pipes to the point where it is uncomfortable for my hand.

These problems don't occur every time either, it will be fine one time and then the next it won't.

I'm assuming that I have a very bad exhaust leak that is causing all these problems but from what I've read on forums is that it could also be dirty throttle bodies among other things so any input will be appreciated.

Car: 2008 G37s Coupe 5AT
Mod List: Z1 Long Tube Intake & GTHUAS Miestershaft Exhaust.

 

If you know your flex pipes are wrecked why wouldn't you just replace them? Then all these issues could be gone. Or not, but at least you won't have the exhaust leak anymore.

 

I should have stated that the car is going into the shop tomorrow to see what can be done and have them fixed. All I am trying to do is get peoples input on whether that would solve ALL the problems that I was having, or if 1 or more of my problems are completely unrelated to an exhaust leak and there is something else that needs to be done. I would rather have it all taken car of within the same week rather then take the car home after the exhaust repair only to find out I still have 1 or all of the same problems. I guess you can kinda say "knocking two birds out with one stone".

 

I really doubt the exhaust leak has anything to do with the rev issue, in fact, it wouldn't make any sense. Sure, I would get your leaks fixed because its annoying but I bet your idle/rev problem are junked up throttle bodies. Have those and your MAF's cleaned and then report back.

 

See the DYI thread on how to clean your throttle bodies. It's easy and only takes about 30 mins to do both. Clean your MAFs while you are at it. That takes about 5 mins each.
(10 if you let them dry before reinstalling)
You will need throttle body cleaner, and MAF cleaner. Don't use either on the other.

Then see the thread on how to reset your ECU. That should help with forcing a throttle / idle reset.

There is also instructions in the Field Service Manual (also in a sticky on this site) and you can look up the procedure to reset your Minimum throttle and Idle. THere are threads on both too.