Why Did My Z, Keep Revving? Video.

ChrisSlicks

I agree with Bobo, sounds like the accelerator pedal position sensor is a viable culprit given these cars are fly by wire throttle.


Section EC (Engine Control System), page 18


ACCELERATOR PEDAL RELEASED POSITION LEARNING
ACCELERATOR PEDAL RELEASED POSITION LEARNING : Description
Accelerator Pedal Released Position Learning is a function of ECM to learn the fully released position of the accelerator pedal by monitoring the accelerator pedal position sensor output signal. It must be performed each time the harness connector of the accelerator pedal position sensor or ECM is disconnected.

ACCELERATOR PEDAL RELEASED POSITION LEARNING : Special Repair Requirement

1.START
1. Make sure that accelerator pedal is fully released.
2. Turn ignition switch ON and wait at least 2 seconds.
3. Turn ignition switch OFF and wait at least 10 seconds.
4. Turn ignition switch ON and wait at least 2 seconds.
5. Turn ignition switch OFF and wait at least 10 seconds.

spearfish25

If this was the issue, then it wouldn't happen sporadically.

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ChrisSlicks

It could due to small fluctuations in the output voltage of the sensor.

1slow370

haha watch this be related to the ETB buzzing from not being correctly grounded

MightyBobo

Correct, it holds it for a moment just incase you decide to press the clutch back in and pop it into gear, but it wont wait forever . After a moment, it just disables, and no more bliping of the throttle.

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IcedZ

Weatherman, let me know what you find out. Mine did the same thing twice. Once per day two days in a row. Mine held at about 2k RPM though, definitely not 3500+. I live in central Florida, so it's not NEAR as cold as you were. I also am over 99% sure it is not SRM. I wiggled the stick in neutral and in and out of gears and let off the clutch in neutral... it was still revving. Both times that this happened it was after a 10+ mile drive on the intersate going about 80. So everything was up to normal operating temperature. Both mornings were cold, but not the coldest that we had. It was definitely bizarre. I cannot get it to repeat anymore now (I'm thinking because it's warmer outside).

m4a1mustang

Well most people don't know a thing about cars... in a panic situation they just stand on the brakes.

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Zsteve

True dat, unless you are used to being in bad situations, when you are in one you wont think like you do when you are watching it or hearing about it, you just do what seems natural and slam on the brakes. Its like making good decisions in any situation, you have to have been there and done that before.

Ever come across those people that can answer every question of a game show while sitting on the couch? Get them at the studio and they freeze up.

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ChrisSlicks

Yes, they stand on the brakes, which of course promptly overheat and stop working thanks to their low noise, low dust organic formulation. Actually it's because they don't hit them hard enough, you need to stomp them hard, probably with both feet if you are a girl or a girly man. Of course the other obvious alternative is to shift to neutral or even shut of the ignition (although that's probably the last thing you want to do in a panic situation).

Here's an except from C & D this month. Surprisingly they could stop the cars only a few feet longer than in the regular braking test.
Full article:
How To Deal With Unintended Acceleration - Tech Dept.

TheWeatherman

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

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.

TamZ

This is exactly what happened to me when a semi-truck forgot I was in front of him at a stop light and he just hammered it and ran right into the back of me..He didn't even know he hit me (how he didn't know, I will never understand!)..I was in my little Nissan 240sx and what did I do? Slammed on my brakes. As if I was going to stop the semi-truck who didn't even know I was down there in front of him. He was shifting gears, had no idea I was there and I was hitting the brakes?!? I should have hit the throttle. I was young and it scared the $#@$ out of me. Totaled my car. I'm lucky to be alive, he pushed me for a couple hundred feet before he realized he was hooked on to the back of my hatchback! (he only noticed because my car, being stuck (his big bumper sort of rolled up on my car I guess?) started to turn sideways and he slammed me into a guardrail. What I remember most about that accident is when he sheared off my radio antenae all I could hear was the static!

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MightyBobo

Bleh, I knew it was a position sensor of some sort...too many new ones in every car to diagnose anymore lol. Glad it was a simple fix though

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semtex

You're damn straight I have an attitude about it. Go back and review the thread starting with post #23, where bullitt5897 first suggests that it might be SRM. A bunch of guys including the OP immediately poo-poo the idea, I chime in and say hey, instead of debating this to death, why don't you just turn SRM off and see what happens? I mean, it's a simple push of a button, it's not like you have to break any tools out. I even go as far as to clarify that while I agree that SRM wouldn't account for this behavior if it's functioning as designed, that doesn't discount the possibility of a malfunctioning SRM being the culprit (post #35). So does he ever try it? Nope. So arrogant and self-assured he is of his logic that he can't bring himself to just push a button to give it a try and rule out the possibility that his SRM is malfunctioning. So, you want to talk about e-attitude? That kind of pig-headedness is the epitome of attitude, IMO. TW says it's great to see this forum work in such a constructive way. Well I'm glad he feels that way. But personally, I found his attitude downright frustrating and, in light of the confirmation that it was SRM all along, foolish and anything but constructive. And if it's rude of me to say so, then so be it. I don't give a sh*t. Flame away.

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m4a1mustang

Well, I thought you were directing it at me. I just want to make it clear that I don't roll that way. If you have an opposing opinion I will hear you out and if you are a constructive member of the forum (and you are) I will always respect your position.

I understand what you're saying about the OP... The battery disconnect was an issue with me.

But that aside, I am not afraid to admit I was wrong. You and Bullitt were right. I didn't think it could have been SRM based on my experiences with the system, but it was.

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