Good Morning, All,

I'm having two big issues with my 2007 G35 Sedan non-sport with 110k miles and they may or may not be related. I've had a couple 'tech' friends look at it as well as the Infiniti house and nobody can pinpoint the issue (Infiniti has had it since Saturday).

First issue: when the engine is in the 900-1200 RPM range, the transmission hesitates to accelerate; sometimes it'll jump back into acceleration, other times it'll huff-and-puff as if its not getting gas. According to the Infiniti house, the transmission is fine and there are no signs of failing and that they couldn't replicate the issue. They also originally said it possibly needed a computer reset, but later realized that doesn't apply to my car. I told them I felt it needed to warm up first before symptoms showed. They test drove it again and said they replicated the transmission issue I spoke of. They still said there are no signs of failing and that "it has 110k miles, its just getting old." Issues #1 & 2 happened too abruptly for it to be a cause of age (IMHO).

Second issue: Not every time, but enough, when my car is accelerating passed 70 mph there begins a violent vibration in the front end. The hood can be seen vibrating just in front of the windshield at a very high rate while giving off a very high, fast sound. The closer I get to 80 the worse it gets. I don't dare travel any faster for fear the car will disintegrate. I imagine a plane hitting Mach 1 that isn't designed to travel that fast and is about to explode into a thousand pieces; the car shakes that much and is that loud. Now, according to the Infiniti house, the vibration came from the rotors when the brakes were applied. Yes, the back rotors probably need replacing (front rotors/pads are new), but the horrible vibration/sounds mentioned above happen without ever touching the brakes. Infiniti test drove it again and said they replicated the hood vibration and are now saying that's from the transmission (back to first issue), but were not sure and needed to run more tests.

At this point, I feel like I'm getting the run-around. He keeps mentioning the rotors and the vibration in the wheel from hitting the brakes, but I know that feeling enough to know that its completely separate from the hood and transmission issues.

Don't get me wrong, I love driving around this brand new fully-loaded QX60 loaner, but I'd like to know what's wrong with my car.

Thanks to all that help!

-Ryan

 

Based off the K.I.S.S. method, I will start the basics for the first issue.
- Have you checked all fluids?
- Have you disconnected the neg side of the battery and left it off for about 20-30min to reset the ECU?
- Are you throwing any codes?
- Have you had any sensors changed or removed recently?

For the vibration, start with the wheels and tires and work your way in.
- wheels tightly secured
- tire tread good
- weights on wheels in tact or correct
- warped rotors, even if new
- loose hub/bearing
- bad bushing

Hard to narrow it down just from reading, but I wish you some luck. I know the run around gets quite annoying.

 

- Have you checked all fluids? Yes
- Have you disconnected the neg side of the battery and left it off for about 20-30min to reset the ECU? Yes, replaced battery one month ago and it sat for several hours without a battery connected
- Are you throwing any codes? No codes according to Autozone and Infiniti
- Have you had any sensors changed or removed recently? No

- wheels tightly secured Yes, we checked them when we replaced the front rotors and brakes.
- tire tread good Tread is good, tires are about half-way worn with no physical issues
- weights on wheels in tact or correct Infiniti house balanced and rotated tires about six weeks ago when attempting to solve the current vibration problem. had no affect on the vibration
- warped rotors, even if new I'll have ask Infiniti, i do know the braking vibrations calmed down when we replaced them but had no affect on the >70 mph vibrations
- loose hub/bearing I'll have to ask
- bad bushing I'll have to ask

I'll have to double-check the last two or three with Infiniti. My understanding after a convo with Infiniti is that there were no signs of bad bushings/hubs due to the lack of noise when the car/steering wheel turns. The 70mph vibration occurs no matter what is happening, i.e. braking, accelerating, turning, yelling, cursing, etc.

Thanks again,
-Ryan

 

As for the vibration, check the rims, one may be bent. I have bent 4 sets of rims over the last ten years. I will make it vibrate even when balanced.

 

How long has each issue been going on?
It sounded more recent than over a month...

 

How about your engine and/or transmission mounts.

 

Update and solution:

Come to find out the fuel throttle/injector needed a cleaning and reprogramming which fixed the 900-1200 RPM issues.

The front end vibration came from a 'cracked' spark plug. According to the dealership, the spark plug was causing a misfire and at high(er) speeds/RPMs, the transmission and engine were "out of sync." I've ran my car up and down the highway at speeds close to 90mph and have had no issue. Come to find out, ~3200 RPM is the "out of sync" threshold, which is rarely reached in lower gears/speeds.

Thank you to everyone who read and helped me out.

-Ryan

 

I spoke too soon. After two days of running well, the vibration in the front end came back. Back to the drawing board.

I'm gonna try again with the tires, rims, and rotors. Then I'll move on to engine mounts.

-Ryan

 

what's the exact service called for throttle/injector cleaning and reprogramming? How much they charged you?