Hello, I have a 2008 G35x. When I start the car it starts to rev up and down, and then turns off.
he only way it stays running is if I floor it, if I do this it revs up and down (300 rpms to 4000 rpms) until it starts idling properly at 800-900 rpms (takes about 10 seconds). After this, the throttle is completely useless and maybe increases the revs by 100.
Does anyone have any clue what the hell could be causing this? I've sprayed MAF's and Throttle bodies with cleaner, still isn't working properly. Any ideas or input would be massively appreciated. It's strange because it lets it rev up when I first start the car (just shoots to 4k) but then once its idling I can only rev 100 rpms.

 

Could be the throttle pedal switch, throttle motor, ECU, any number of things really. Is it throwing an error code? When exactly did this issue start, has it gotten worse over time, what were you doing BEFORE the issue happened, etc. No such thing as too many details when asking for remote troubleshooting.

Did you unplug ANYTHYING?

 

There is currently no CEL code. This issue started maybe a month ago, but if I turned the vehicle off and on it would go away and it would only do it maybe once a week. I figure it may have something to do with the o2 Sensor as I had a code present a few weeks ago. I also noticed when I plugged in my DTC Scan tool that when I was revving the Throttle Position % would not move, except for the first second or so when it runs. When I start it I can rev it up but only for about a second. Not sure if that has any relevance to the o2 sensor. You're right, this could be a host of issues but I'm not sure how to find out and am not in a position to be spending thousands at a shop.

From my research, similar problems arise from o2 sensors, thottle body, throttle position sensor. Not sure how I can test any of these and I feel like a trouble code would come on if those were the case.

 

It's probably only an hour of labor at the nissan dealership for a diagnosis. It's not as expensive as you're thinking.

However, if you DONT have a CEL then you aren't actually in limp mode, this is why I think the pedal switch is shot. If you were actually in limp mode then it's because the computer recognized a bad signal from a sensor and is actively restricting your throttle output and rpms. You don't have a CEL, this would be easy to check with the OBD2 scanner, when it's malfunctioning look to see what % the throttle switch is sending, push the pedal wide open throttle and it should be reading 100%, if it's reading a really low % then you have probably isolated the problem.

The actual SWITCH is only about $20.

Something else to do is a pedal reset:

http://www.nicoclub.com/archives/g35...procedure.html

It's important to use a timer that shows the seconds, timing is important and it might take you a couple tries (or many...) to get it right.

Lastly, you could have a seriously clogged catalytic converter but there is TYPICALLY a rotten egg smell and CEL's when it's that bad.

 

The throttle position reads 3.5% and won't increase when I press the pedal. However, For the first second or so the vehicle lets me rev it and the % will go to whatever I rev it to. Kind of strange cause it works for one second when I start it and then it stops working. Still think this is characteristic of a bad throttle position sensor or pedal switch? And if so, can you please link me to where I'd find this part?

 

I'm definitely thinking it's the pedal switch, if it was TPS you would be an error for bad data comparison between the pedal and the actual TB. The system basically works like this.

-ECU receives input from pedal switch
-ECU sends data to actuate throttle motor
-ECU verifies throttle motor position via TPS

If the verification step fails you get a check engine light, I think it's simply getting the wrong input voltage from the pedal. It CAN be tested as well, there are steps in the FSM to use a 3 battery holder for AA batteries (1.5vdc x3 = 4.5vdc which is close to the 5v it normally operates at). You hook up the test batteries to the switch and use a digital multimeter to read the voltage coming out as you operate the switch, it should scale from 0.5v-4.5v for one part of the switch and 1v-5v for the second part (it's actually TWO switches).

Fortunately this is also one of the FEW electrical components that it's not strongly recommended to use a factory OEM nissan part. A replacement from autozone/napa/etc is cheap ($20-30) and will work just fine.

 

Okay I'll give this a try right away. Where exactly is this switch? And do you have an image or part number for it? When I google for this part all I come up with is a brake light switch or the tps. I called Napa and they said $250, so I'm sure they weren't talking about the same part.

 

They were probably trying to sell you the entire pedal assembly. If you look down at your accelerator pedal there's a harness coming out of the top right side of it., the switch itself is held in by a couple screws and can be replaced separately from the pedal assembly.

I didn't watch this whole video but this should give you an idea of what part it is.


Your pedal has a plastic cover over the top of the linkage, that vid was from an older G35 and there was a revision somewhere along the timeline but the compatibility of part should be the same '03-'08 used the same switch.