Hello,

I bought a G35 a month ago and while changing out the spark plugs I moved decided to clean the body throttle (bad idea, didn't know at that time) after cleaning them I got the dreaded issue with the idle surging and rpm being all messed up. well after 2 weeks, I managed to get the idle relearned ( with a NDSIII app for android .... ) while 2 shops, Nissan dealership and another Nissan tech couldn't get it under control.

Now my concern is the idle, to me it seems that it is too high on cold start ups. When I start it cold it jumps to around 2000 rpm and slowly in a couple minutes drop down to ~650 .
When driving at around 60 mph and releasing the gas pedal, the rpm seems to want to stay at around 2000-2400 range, with my experience with other cars it seems that with others the rpm drops down to around 1700 rpm when I release the pedal.

So my question is, could this be a problem with the MAF sensors being bad?
I recently got the P0420 and P0430 codes for the catalytic converters, but I asked around and bad cats would cause the rpm be lower than it usually is if they are correct.


Thank you,

 

Both of those descriptions sound totally normal. These cars have always had a fairly high startup rpm, and if you are in gear and moving anywhere near 60mph and coasting you should be in that rpm range due to the gearing.

If you want to verify the idle will return properly when you're at 60 mph, just let off the gas and then pop it into neutral for a few seconds. You should see the rpms come right down to idle.

 

Thank you, i was just worried since i have had this car for a month and haven driven less than that due to the TBs messing up.

Another thing that seems weird is when driving around that speed and suddenly coming to a stop the rpm needle kinda jumps up and then down. It feels like the car messes up on the gears and doesn't know which one it should go into .


The car is automatic by the way.

 

^^ Yeah, on hard decel, the rpms will always be tied to the tranny downshifts, so if the tranny is shifting clumsily then you will get that effect.