Higher than normal RPM
 

Hello Gents,

I'm a new owner of 2007 G35x, I've been browsing this forum during my search for my G35 and I learned good stuff from it.
I've a question and would like to listen to you based on your expertise and experience.

Recently I've noticed something higher than normal RPM on "P" (between 1000-2000), as soon as I switch to any other gear or even "N" it drops to normal rage (slightly below 1000).

While I'm driving, RPM gauge shows normal behaviour, and its drops below 1000 while stopping at signal for example. The AC does not cause any abnormal high revs as well.

I don't know what that could be!'

I'd like to know your opinions please.

Thanx.

Pretty sure your idle should be around 650 +-50 without the AC on. Either you have a vacuum leak, dirty throttle body, etc..

Look up the procedure for resetting the idle air volume.

Thank you coffeysm for your reply.

If it is vacuum leak would it still behave normally on neutral?

For info, the car has about 94k km and I use premium 91 gas (if that of any importance).

With a vacuum leak you might a hear hissing or suction noise from the engine. It will mostly affect you when you're idling, sitting still, etc.. When you give it gas the throttle opens up more, so the extra air that is being sucked in is kind of trivial at that point.

How long has it been like this? It should set a P0507 engine code if it's been awhile and/or P0171/P0174 for running lean. If it's a vacuum leak that is.

Some other things are maybe a dirty MAF, bad throttle body, dirty throttle body, etc...

Need a little more information before figuring out what the problem can actually be. The car will stay high in RPMs until it enters closed loop where it should settle down to 650 +-50.

If you have OBD tool that can read live data that would help.

I just bought an 08' G35x and have the same issue. Did you figure out what was causing the high rpm in park?

Have you checked for vacuum leaks, that's almost always the culprit.

I've haven't done any proper leak test but I also haven't heard any sucking that would indicate a vacuum leak. First thing I'm going to do is clean the throttle body's when I replace my intakes.

when the motor is cold this is normal, when i move my shifter, the rpm's come down so as to not jerk car into gear, my car has done this its whole life, or if i leave it run a minute or two, the rpms will slowly come down, i presume this aids in motor warm up. when i start car hot, idle is around 700.....

Does it do this all the time or only when cold ?

What is "high" RPM ?

Only when cold, and it idles between 1000-2000 rpm

That's normal. Drive the car for 30 minutes, shut it off, then re-start it 2 minutes later. Now check the idle.

Cars have a cold idle speed (higher) and their normal idle speed.