Help, throttle override by the ECU (not due to riding the brakes)
 

In my attempt to fix my piece of $hit, it looks like my hesitation is actually my ECU snapping the throttle shut upon acceleration. It doesn't seem to happen often at WOT, but it just does it at random times. Obviously the harder I am on the gas, the harder it would cut. I don't know if the ECU is snapping completely shut or leaving a little open like the brake override the car has. I have tried to adjust the brake lamp and cruise brake switches, it doesn't seem to do anything. I have even tried to unplug it and pin it, still no help. Do you guys have any idea? I also get no check engine light since the car isn't misfiring, it is just closing the throttle on me even though I am asking for gas.

The only other symptom I have is that the cruise control would sometimes cut out on its own, but the shop manual on the forum doesn't have that section....

You tried hooking it up to a datalogger and seeing whats happening?

Yeah, TPS goes to 15% randomly. My engine is not misfiring, it's just my throttle is shutting off, exactly like I am hitting the brake override

That is very interesting. When does it usually happen? Completely random? Like VDC is invading even though it is off? I have only experienced what you are describing if I forget to disable VDC. The rest of the time, she will go on command. What have you changed/modified already? I know there are a lot of questions here, but I am trying to understand how to assist you in isolating the cause.........

Did you check the brake pedal switches? I had to add a shimmy for one of the switches, and it did alleviate the random throttle cut issue a year ago.

When does it happen? I get something similar after moving from around 15% to 40% or more.

it looks like i found the problem. it looks like a combination of three issues

#1 brake light switch (mine was out of adjustment, had to crawl under to adjust it), it was causing my cruise control to kick in and out when i first started.
#2 baffle plate broke inside my gas tank at 12000 miles
#3 here is the big one. the way nissan wires are put together in the tail light, you cant wire the trailer light kit like a normal car as the blinker light would trigger the brake override since trailer share the taillight with brakes and blinkers. the hesistation i experienced was actually the ecu shutting down the throttle on accel as the blinkers blinked. its the same reason why my car would mostly do it out of a turn and the mechanic didnt get it since he never used the blinkers. i have to modify my wiring harness to fix that. i cut the right side wire, so now i can use my right side blinker and not get hick up. yet as soon as i hit the left sife my theottle would go limp again.

with all that said. i have to apologize to nissan as this wasnt really an electrical bug caused by them. the dealerships still suck as now my alignment is all screwed up after they dropped my rear suspension to fix the gas tank. moral of the story, dont hack up or race the car.

Wow that's a pretty amazing story. Who would of thunk it? So your not going to trade in the car now? LOL.

How did you figure it out though?

Seems like modern cars are going to need less intrusive mods - like a brake light kit that only uses power and detects car lights using an optical sensor :)

Wow. Glad you figured it out!

Skills....Just kidding, it was pure dumb luck.

I spent two hours Saturday night driving around town to gather some datalogs. Using the OBDII logger, I was able to see that my engine actually wasn't misfiring. It was actually triggering the brake override safety system (the same reason why people can't do standing burnouts). We drove around at different times and we honestly couldn't figure it out. I then went to an autox hoping to break the car, of course the car drove fine and performed well as I didn't use blinkers on the course. As I was driving home, I noticed my cruise control would cancel on its own again even though I had readjusted my brake pedal switches. I kept using it hoping to catch a pattern on when it cancels. That's when I realized the cruise control would kick off whenever I use the blinkers. I then remember the trailer light is put together with a kit that you have to tab into the brake light and turn signal light. Since trailers don't have a separate brake/turn signal light, I realized it must be that triggering the brake override. I drove around for another 30 minutes and confirmed it was indeed the case (I use my blinkers when I turn, hence all the hesitation exiting the turn). This morning I cut the wire for the right turn signal, sure enough I can now use my right blinker and get full power again. I still can't get the car to stop hesitating on left turn as the trailer light box is behind the bumper, I have to remove it if I want to fix it for good. I was really angry about the car as my old Mercedes and Corvette had electrical problems, thank god the electrical bugs haven't moved to Japanese cars yet. So sorry Nissan for accusing you for getting the electrical bug, still, your dealership sucks as my car now crab walks on the highway thanks to them not aligning my car after a new gas tank.

The cars I want haven't gotten cheap enough for me to buy yet, so I will probably keep the Z now I know that there are no factory made electrical issues.

So what data logger are you using? I'm currently looking into some.

Repped for figuring this out on your own and for sharing solution. With this being resolved are you still going to keep the Z?

You can fix your wiring by adding a couple of high-current diodes to the trailer wiring harness, need to prevent the blinker voltage feeding backwards into the brake light and vice verse.

I still find it weird the way Nissan wired the brake kill circuit slaved off the brake lights themselves, but I guess it makes sense in a weird way.

BTW I told you it was the kill switch, just didn't think about it from that end of the car. :)

I just got a cheap scanner, it was the cheapest thing I could find.

http://www.amazon.com/ElmScan-Compac...4064273&sr=8-3

I sort of created the problem, so I am definitely the retarded one, can't blame the car even though I am still pissed the gas tank and the brake switch all went out of adjustment at the same time.

Chris, thanks for the great idea. I was just going to put a SP switch, figure I will use that to stop myself from driving fast with a trailer hooked up. I can test it now since my right turn signal is exposed right now. Which diode should I put in, I seem to recall they have different resistance.

I was really going to trade this in, I have an excellent offer on a Honda Pilot now. Problem is that the one I want is $4K more, plus the Prius is no fun at the autox and the Pilot can only tow 4500lbs. 4runner is nice, but the one I want is $33K, I don't want to spend more than $30K. Which brings me to buying a "used" autox car and save up for a race car, but the used cars I want to buy are almost more than my Z. So until I find an orange TTS for $20K, I might be stuck with the Z for a while now that it is fixed (well almost since my left blinker is still fu*ked)

Thanks for the support guys