Strange problems - Tell me what you think
 

2009 G37xS, 27k Miles

So, I had driven down to my mothers house for Mom's Day last weekend, which is about 350 miles. I had driven the long distance and everything was fine. Later in the weekend I had just exited the freeway and was doing about 40mph on a surface street. I was just maintaining speed when the car started to shake, I felt the vibrations, then noticed my RPMs were stuttering (oscillations of about 100RPM), and the gear shift was shaking back and forth. When I let off the accelerator the vibrations went away, but when I put my foot back down it came right back. I took my foot off the accelerator and put it back again and there was no throttle response at all, like the accelerator wasn't connected to the car. So I pulled over and idled to a stop, where the car was idling just fine - no sputtering or noise, nothing. Restarted the car and the car acted fine.

I had to get back to Denver later that day, so I had no choice but to roll the dice with my car on the drive home. The drive home was fine except for one hiccup: I had to brake hard going from about 75mph to 40mph, and when I went to accelerate again the transmission didn't shift, there was throttle response from the engine, but I was in 7th so there was no power. I lifted and put my foot down on the accelerator and the transmission made a hard shift down to what I believe was 4th, and I was on my way again.

My maintenance is up to date, and I always put in the highest octane gas I can get in Denver (usually 90 or 91). I'm taking the car in tomorrow morning to Infiniti to figure out what is wrong. I've had some of the usual gripes with the transmission (hard shifts etc.), but I haven't heard of anything like this.

Any thoughts? I'll update when I know.

take it in to the stealership. it's still under warranty.

Sounds like a trans issue. My guess is either a sensor is failing or the trans is. I had Similar issue (different make/model) and One of the celloids failed and needed to be replaced.

Sounds like your tranny is not catching the gear. Possible cause tranny or your timing belt is the main cause.

You should record it if it happen again. You can show it to the service advisor. If u bring your car in and they can't duplicate the problems they will not fix anything!

Certainly sounds like a tranny problem. Definitely take it in since it's covered.

Dropped the car off the morning, gave them a full run down of my experience. The service adviser I talked to told me that on some of the 2009s the ECM doesn't properly communicate with the transmission. The fix is a replaced, or reflashed ECM as well as some updated software on the transmission control. I'll let you know what the final diagnosis is, and what they did to fix it.

Just talked to the dealer - they reprogrammed the ECM and told me to drive it for a week or two and see if the problem was addressed as it was intermittent. The service tech I talked to told me he had seen a few 2009s like this, and the reprogrammed ECM did the trick. I'll update if it doesn't work.

2009 G-37 ECM - transmission problem
 

This exact same problem happened to me in my 2009 G-37 Journey sedan. I bought it new and only had 5,000 or so miles on it. Same symptoms - same diagnosis. Dealer "reprogrammed" both the ECM and the transmission. Have not had the problem since. Scared the beegeebers out of me when the problem occurred - as I was in the middle of remote and wild New Mexico at the time. If we had broken down, the coyotes would've had a field day! :eek: