Why Did My Z, Keep Revving? Video.

TheWeatherman · 02-03-2010, 10:56 AM

Hey ChrisSlicks, thanks for posting that C&D article. I see that Nissan/Infiniti has that throttle cut feature. For some reason, mine didn't do that. It was pulling faster with my foot on the brake. Here's the catch, I didn't slam on the brake, I just hit it light/moderate. (I was getting close to an exit on a 55MPH highway. I just hit the clutch and coasted down the ramp after I could feel the car pulling on me. It was speeding up over 60MPH with no cruise and no foot on the gas.) I wonder if there's a threshold of cutting the throttle. As I came to my first stop, I was revving over 4,500 RPM without any let-off on the RPM. Of course I knew to just hit the clutch and let the car do it's thing. It didn't feel very nice trying to have a decent start and burning the clutch though. I'm pretty sure if I would've popped it, the wheels would've slipped a bit... That's how much throttle was being applied to the car as I was taking off. She was on a mission, and that mission was to keep on revving. I still haven't heard a peep on what happened. Your C&D article makes this even more bizarre. I'm still positive it wasn't my floormats because when I got to my first "revved" stop, I pulled my floormats away from the pedal. I really just thought it was my mistake. 4,500 RPM is really up there. I started taking a video after I restarted the car twice. That was about 8 minutes after the 4,500 RPM events. Just trying to put it all in perspective for you.

ChrisSlicks · 02-03-2010, 12:13 PM

With the throttle cut feature on the Infiniti and our Nissans, you do have to press the brake reasonably firmly. With the brake pressed the throttle input is cut back (but not cut completely) if the throttle input is moderate to high. If the throttle input is light then it will let you press both pedals at the same time and wont interfere.

As it doesn't take a lot of throttle input to rev to 4500 rpm unloaded (out of gear) I'm guessing that the throttle input signal wasn't high enough to warrant a throttle cut. Even with a throttle cut you would feel the car pull on you a little as you braked but it would be easy to overcome by braking firmly.

Would be interesting to see what voltage the APPS (accelerator pedal position sensor) is sending out in the misbehaving case. From that you could determine if it was a bad sensor or if the ECU needs to recalibrate a new up-pedal voltage. Bad sensors are rare because they do send out 2 redundant signals. It could be that the dealer screwed up the calibration by disconnecting the harness when you took it in for something else. I'll check if the car sends out throttle position or voltage as and available data point on the OBDII/CAN.

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02-03-2010, 10:56 AM	#1 (permalink)
TheWeatherman Enthusiast Member Join Date: Mar 2009 Location: Milwaukee, WI Posts: 265 Drives: 2009 370Z 6MTw/Sport Rep Power: 17	Hey ChrisSlicks, thanks for posting that C&D article. I see that Nissan/Infiniti has that throttle cut feature. For some reason, mine didn't do that. It was pulling faster with my foot on the brake. Here's the catch, I didn't slam on the brake, I just hit it light/moderate. (I was getting close to an exit on a 55MPH highway. I just hit the clutch and coasted down the ramp after I could feel the car pulling on me. It was speeding up over 60MPH with no cruise and no foot on the gas.) I wonder if there's a threshold of cutting the throttle. As I came to my first stop, I was revving over 4,500 RPM without any let-off on the RPM. Of course I knew to just hit the clutch and let the car do it's thing. It didn't feel very nice trying to have a decent start and burning the clutch though. I'm pretty sure if I would've popped it, the wheels would've slipped a bit... That's how much throttle was being applied to the car as I was taking off. She was on a mission, and that mission was to keep on revving. I still haven't heard a peep on what happened. Your C&D article makes this even more bizarre. I'm still positive it wasn't my floormats because when I got to my first "revved" stop, I pulled my floormats away from the pedal. I really just thought it was my mistake. 4,500 RPM is really up there. I started taking a video after I restarted the car twice. That was about 8 minutes after the 4,500 RPM events. Just trying to put it all in perspective for you.

02-03-2010, 12:13 PM	#2 (permalink)
ChrisSlicks A True Z Fanatic Join Date: Mar 2009 Location: North East Posts: 6,203 Drives: 09 370Z Sport M6 Rep Power: 654	With the throttle cut feature on the Infiniti and our Nissans, you do have to press the brake reasonably firmly. With the brake pressed the throttle input is cut back (but not cut completely) if the throttle input is moderate to high. If the throttle input is light then it will let you press both pedals at the same time and wont interfere. As it doesn't take a lot of throttle input to rev to 4500 rpm unloaded (out of gear) I'm guessing that the throttle input signal wasn't high enough to warrant a throttle cut. Even with a throttle cut you would feel the car pull on you a little as you braked but it would be easy to overcome by braking firmly. Would be interesting to see what voltage the APPS (accelerator pedal position sensor) is sending out in the misbehaving case. From that you could determine if it was a bad sensor or if the ECU needs to recalibrate a new up-pedal voltage. Bad sensors are rare because they do send out 2 redundant signals. It could be that the dealer screwed up the calibration by disconnecting the harness when you took it in for something else. I'll check if the car sends out throttle position or voltage as and available data point on the OBDII/CAN.