I bought this G35 last November in New Mexico (high altitude). It had the GReddy TT and all of the engine mods listed below and it ran great, putting out 340 rwhp. I drove it back to Las Vegas and it still ran well, even as a daily driver. Then the weather started getting warmer. The first problem that I noticed was a loud backfiring as soon as the key hit the "on" position on the ignition, but before the engine is started. This happened about every 2nd or 3rd start. Then the car's hp started "feeling" like it was down - later confirmed by a dyno test showing rwhp down to 270. Next came the check engine light, and finally the idle problem. The baseline idle is around 1200, and once it gets going the idle does this "revving" between 1000 and 2000 rpm in 2 second cycles before finally settling down at 1200 rpm. While driving, the throttle seems to want to surge and wants to push the car faster than I want it to.

I found a seemingly competant tuner (rare in Vegas) who dyno'd the car and felt that the fuel mixture needed to be leaned out. The combination of that and bumping the boost up from 5.5 to 8 psi got my rwhp back up to 330. He then referred me to the Infiniti dealer to get a senser reprogrammed that should have taken care of the idle problem.

I then take it to the dealer, they plug in their CONSULT computer and it tells them that my ECM computer is bad. $1400 later I have a new ECM that their CONSULT (should be INSULT) computer says is fine, yet I have all of these problems still occuring. When I asked if they'd looked at the throttle or crank or cam position sensors, they told me that their computer didn't show anything wrong with them.

Has anyone experienced anything similar to this? Anyone have any GOOD advice? Thanks in advance.

 

it sounds like your engine is sucking in unmetered air (somewhere).


Check for loose hoses, vaccum lines, manifold gaskets, etc.