Z does not accelerate

MikeUCFL

Anyone know if one of those cheap elm327 OBD readers can read acceleration/brake positions? If so, you may be able to spot this using one. Otherwise, maybe cleaning out your MAF sensors with some CRC MAF cleaner could help?

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Magnetic Black Touring/Sport/Navi/6MT < Stillen G3 | ZSpeed Stage 1 Clutch/Flywheel/CMAK | RJM Rev 3.2 Pedal with Tilton Master

ZeN

Yes...obd2 elm327 with torque pro with paid Nissan Adv plugin theres brake switch parameter. It will let you know if your brake switch is on if its not. On off value only.

MikeUCFL

Ah, good to know

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Magnetic Black Touring/Sport/Navi/6MT < Stillen G3 | ZSpeed Stage 1 Clutch/Flywheel/CMAK | RJM Rev 3.2 Pedal with Tilton Master

thompsontechs

Be sure and let us kn ow when you get it figured out... nothing worse than having the same issue and not seeing an answer at the end.

P's_Z

Thanks. Ive experienced issues with dirty MAFs before, but usually the symptom is hesitation. No harm in trying this out though, as i have some CRC MAF cleaner around. 5 days of driving after the issue happened, no problems so far

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Zeta

chii370

sounds to me the fly by wire throttle is failing in some way. they can act several different ways when they fail from not responding at all to input, to reving up and down on their own to going full bore. just my opinion.

thompsontechs

This seems possible as well, perhaps a positioning sensor failure. The more stuff you have in the design, the more there is to fail. I do not like fly by wire stuff myself... give me a good old mechanical connection. Hey. I'm old!

juld0zer

2 switches near the brake pedal. disconnect the left one, then fit a jumper across the connector on the harness side (jumper the male connector, not the switch which you have now disabled)

nb: disconnect battery as it's very easy to accidentally short something while fitting the jumper.

jumper can be a big staple, wire or whatever. tape it up to insulate after

P's_Z

Sorry in advance for the question im about to do, but: how would this help and what possible risks am i looking at? Sorry, but never heard of doing this before.

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Zeta

juld0zer

have a read of my thread, esp the last page: HELP! Severe acceleration lag

the switch on the left is mainly used to kill the cruise control when you brake. the switch on the right is for the stop lights so dont worry, your brake lights will still work as they should.

the left switch is also used to tell the ECU when you are braking (don't ask me why Nissan chose to use two switches...) and in a bid to prevent a runaway Toyota situation, the ecu will not let the throttle plates open more than 15 degrees (until you pass 4000rpm) if it detects the brake pedal is pressed. Think of your garden hose when it gets a kink, then you unkink it... wet tshirt due to sudden increase in water flow etc.
I've actually discovered thru a lot of experiments that if your foot is on the brake pedal, the ecu will not let you accelerate faster/open the throttle plates further than its position at the moment you pressed the brake pedal. until you eventually pass approx 4000rpm.

So, if your brake pedal switch is not adjusted correctly or faulty and the ecu is misled to believe your foot is on the brake pedal, grandma's going to leave you at the lights while you're swearing and cursing.

This particular switch on the left is a normally open switch so when you press the pedal, the switch is NOT depressed and therefore circuit is open. The one on the right is normally closed.
So the jumper trick fools the ecu to always think the brake pedal is NOT pressed, by simulating a closed circuit - as if the brake pedal was at rest (which means the switch is depressed).

Eventually, the lag issue will appear again. I think it's because the ecu's failsafe is to assume the driver has to press the brake pedal at least once in X minutes of operation or Y distance has been travelled. I havent triggered it often enough to notice a pattern but both times when the issue reappeared with the jumper in place, it was after driving in heavy stop/start traffic.

hope that helps see what the dealer says/does and then try my get-you-home trick if they cannot solve it

juld0zer

cleaning the throttle bodies and performing the 3 relearns did not cure my random significant drop in throttle response. Like replacing all the VVT seals and o-rings, it cured a different annoying problem - sagging idle when stationary.
After cleaning and relearning, my idle throttle position is 0* according to my Scangauge 2 device. TPS voltage is about 0.55V according to Cipher. Before it would idle around 3*/0.6ish volts. So that tells me the throttle plate was probably held slightly open by carbon build up. So not a complete waste of effort. Glad to sign off on that one. I'll probably set myself a 1.5-2 year cleaning interval for the throttle bodies.

At this point, i have no choice but to delve deeper into the workings of the VVEL system to try and resolve this ongoing issue. With no local dealer support or technical experience, i am left to battle this alone. i might make a few phone calls to some Z workshops in the US to pick their brains

P's_Z

Sorry to hear that my friend

Keep us updated on this

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Zeta

Business Kat

Ya'll were right. It may be too early to call it but I think we solved it!!

Stillen makes a very high quality throttle position sensor extension that comes with their kit. The technology in this sensor is incredible. It's able to absorb heat and far beyond any cable I've ever come across.

Sarcasm aside, the sensor overheats and will start with false voltage readings and ultimately will cause the car to go into limp mode. This is why idle RPMs go wonky, random cuts in power will occur, and why the cars will go into limp mode.

Someone at Uprev had the same problems as me so they were able to fix it pretty easily. I can't believe this $40 cable and a $5 plastic elbow join cost me thousands in damages and repairs. Stillen told me the plastic peice wasn't covered under the warranty and when I contacted them about the TPS they said the warranty was only good for a year. Can't express how dissatisfied I am with Stillen.

I'll update again but I already can tell there's a massive difference driving it.

juld0zer

So a bodgy throttle body harness extender was the cause?

P's_Z

Hey guys, unfortunately posting back in this thread as i have "the same" issue with hesitation between 2.5-3.5k rpms again, except this time cleaning throttle bodies has not worked. I also cleaned the maf sensors, air filters are clean, reset ecu, checked and "reset" brake switch, checked for intake leaks, using same 93oct fuel as always, oil temp is good and in operating temps when this happens, recently changed engine oil and its topped up and drove the car a few days before this and all was good. In other word, im frickin' stomped!

Rain has been pouring here in PR the last few days but i havent taken the car out much, plus no flooding in my area.

Taking it tomorrow to the dealer to see whats going on.

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Zeta