So my 2008 G37 coupe is now at 101,000 miles. My car would drive completely smooth and normal until after 20-45 minutes driving my idle would be loud and my rpm would rise to 900 while idling, after I brake my car tries to lunge forward a little bit, and would keep rolling if I have my foot off the brake and not even pressing on the gas pedal. It would completely reset once I turn off and on my car but would happen again 10 minutes later, turning on the AC makes it worse as well. I have cleaned my throttle bodies, resetted my ECU but that doesn't seem to help out. Please help!

 

Have you tried to pull possible codes? Sounds like a MAF or throttle body problem but codes would point you in the right direction.

 

^What Ape said, it sounds like a maf/tb issue. Mine idled more smoothly after a good clean. Although, it does flucuate to around 900 with the AC on during a hot day. As for the lunging problem, I have no idea and just expect it to happen.

 

I'm a newbie at this sorry but if it is a TB issue do I need to get them replaced? And if it's the MAF I just need to clean them?

 

It could very well be a combination of both. You can buy throttle body and MAF cleaner at any auto parts store. No, you do not replace anything. It's a pretty easy diy job with basic tools.

 

MAF

 

If you go to the auto parts store, most of the big chains can pull the codes for you. Start there. At best verything could need a cleaning and at worst you might have to replace something.

What other maintenance has been done to the vehicle recently? Have you replaced the plugs? At that mileage, there's a lot of little things to look at from plugs to fuel injectors to various gaskets, belts, etc.

 

My car ('08S Coupe) w/ 87K miles had the same idle/lunging issue. Shut the car off, restart, and it is fine, only to act up again. You can clean the TB's and MAF's, and do the Idle Air Relearn Programming until cows crap Moon-Pies, it is good maintenance but, in the end, this does nothing for this issue on some cars.

If the last 6 digits of your VIN are under 115669, take it to a dealer, Nissan or Infiniti, and have them reprogram the ECU per ITB07-048B. Mine did it for free but should cost less than $100. I have never had a problem since and just hit 102K miles.

For reference: http://www.infinitig37.com/TSB/1RZ20.pdf

 

Thank you so much guys and I haven't changed the plugs yet but I am going to soon, another problem I forgot to tell is that on a very hot day, or when I have the AC on for like 10 minutes I would hear LOUD creaking coming from the bottom of my car when I would go over a bump or if I would cruise slowly. It would also get worse every minute. Then after I turn off the car it would go away after it cools down. I'm guessing it's my swaybar bushings?

 

Our '08 G was "just not right" as it was knocking on the door to 100k miles. Our mechanic could not pinpoint things so with that and other circumstances we decided to trade it in.

 

Yeah I tried to pull out codes but nothing came up

 

Sounds like ac pulley and serp belt

 

I seem to be having the same problem. The car continues to lunge forward when braking and idles at about 800 rpm. Have you resolved this issue?

 

I just saw a video on you tube last week about after u clean throttle bodies & reset ecu u have to do3 relearn procedures with pushing brake pedal & counting so many seconds between each relearn cycle- if u search on YouTube it should pop up - I’ll try & find a way to attach link video

Hopefully u can troubleshoot everything & fix it

 

Sounds more like you got a small vacuum leak given miles and age of your car. Check the vacuum lines going to intake spray soap water on them while car running if you see bubbles you got cracks in hose