I lose all power under WOT??? WHY??

[rtkota5point9]

So when I'm driving my car and give it WOT, it will go for a bit, and then just die. The engine doesn't stop running, but decelerates and even if I keep my foot right to the floor it will not do anything at all. It doesnt do it every single time, but most of the time.

It even does it in neutral. I can't rev it up real fast or it seems the gas pedal just stops working for a few seconds. I need to just et off for a few moments and then accelerate again.

When driving, as long as I dont give it WOT, it seems fine....

ANYBODY HAVE ANY IDEAS???

[zilla32sgt]

my first assumption would be your car isnt getting enough air (and flooding) or getting too much fuel (and flooding under WOT) check your MAF (mass air flow sensor) you can clean it with a bit of carb cleaner. just be careful with it its very sensitive.

another thing is your injectors can be goin out. they cant keep up with the fuel demands when under WOT.

how long have you had the Z? when is the last time it was fully serviced?

[rtkota5point9]

I just bought it. Injectors seem to have been changed. At least the connectors have. As far as flooding, I don't think so. It's instantaneous. It basically just shuts down. The engine doesn't die, it feels exactly like you just let off the gas pedal. Like it's going into fuel cut.

[nicknasser300z32]

alright dude along with cleaning your MAF i would clean your air filter and check all your clamps connecting your intake piping to see if theres air leaking in anywhere due to a not tightened clamp

oh and what year is your car if its 95+ i'd suggest getting a diagnostic at your local autozone if its pre 95 then look up how to pull a code on your ecu

[rtkota5point9]

I did find the clamp on one of the hoses from the outlet of the turbo to the IC on the pass side was loose right after I got the car home. But that has been tightened and all other seem fine.

Air filter is brand spanking new. I will clean the MAF.

WHat boggles me is why at even like 95% throttle it seems fine? It seems to only be at WOT. TPS maybe?

It does have a S-AFC on it, but I beleive it's just running stock boost. I am going to ditch the S-AFC if it is in fact stock boost, but is there a setting in there that could be causing this?

EDIT: Car is a 91 TT 5spd. OBD-I Will it give any codes even without a CEL? The light does work and is not on.

[nicknasser300z32]

zer...ading

my check engine light doesnt always work...of course my ecu wont always throw a code when it should but this should save anyone from having to go to a dealership. it doesnt hurt to check

[zilla32sgt]

checked your vacum lines?? all fuel lines?

[plane16j]

i got the same problem. it didn't start doing it until I adjusted the throttle to open up farther at 100%. im going to extend the pop charger closer to the bumper vent to see if it helps.

this problem is so annoying!!

[rtkota5point9]

Ok so I checked codes and got 14, and 34. Speed sensor (Which I kinda knew cuz my speedo don't work. lol and "Detonation Sensor"

Now this could have been one of the sensors that i found unplugged/hacked when I cleaned up the wiring under the hood, so it may just be from that. I take it when you check the codes it clears then right?? Because when I checked again right after it said "55" No codes.

I'll check again after I drive home tonight. Where is the knock sensor located on the engine?

[md4040s]

hmm, just off the top of my head, i would think knock sensor would cause the opposite effect if was causing problems. it would put the car into limp mode, where you would only lose power before wot.

your scenario sounds to me like a boost leak that is only cracking apart when it sees enough boost. don't have the directions handy to test that but a simple search for "boost leak tester" would give you more info. good luck

[rtkota5point9]

Ok, so no more Det sensor code.

Only the speed sensor code. Anyone think it might be that? Maybe it thinks I'm hitting speed limiter or something weird like that so it shuts off??

[tg]

seems like an electrical cutout... I know if the cas is disconnected while running at any rpm the engine will shut itself off. If you try this while driving the momentum of the car will keep the engine turning and the electrical will stay on but the ecu will stop firing the injectors and the coils...

That would definitely through an ecu code though...

If your speed sensor is cooked or disconnected (or likely its wire is severed/corroded as its in a very susceptible position for that) it is possible that the ecu thinks its at max speed and cuts out, but I don't think it would do this in neutral.

[rtkota5point9]

I've looked at the wiring for the speed sensor and it all seems fine. I'm gonna try physically unplugging it and seeing if that changes anything.

[vape-one]

I know this may be stupid of me but what is WOT??

[rtkota5point9]

Wide Open Throttle

[VigorousZX]

looking into AIV's and the cats too

[rtkota5point9]

What's AIV? And Cats have been removed.

[VigorousZX]

What's AIV? And Cats have been removed.

AIV valveshttp://www.twinturbo.net/nissa....html

Im not a mechanic, but Im just making a wild guess

[Zwicked]

Have you tested the Throttle Position Sensor? Maybe it has a dead spot a the top of the range. The other item I'd check is fuel pressure. Maybe your pump is going and it can't keep up at WOT.

I would also test the speed sensor, if you got a code there's a reason for that.

[Q45tech]

Measure WOT high rpm while driving FUEL PRESSURE it must be 43.4 psi. corrected for boost.Common for worn out fuel pumps to take out tri-speed FPCU.

[x0paladin0x]

first off ... does the car feel like no AIR .. or no FUEL ... (u can tell if a car is running rich by the smell of fuel and sometimes black smoke out of the tail pipes) if ur not getting enuff fuel these r sum suggested steps

first run WOT .. observe fuel pressure .. if not in specs then start looking for a weak fuell pumps .. the TT has a 2-stage fuel pump .. low speed under normal conditions ... the a high speed under boost conditions ... symptoms of the problems .. this is a likely step .. theres a high speed fuel pump relay that energizes the high speed input into the fuel pump. I wldnt think fuel filters as that problem is usually consistent across the board.

also cld be a simple problem as looking at ur spark plugs. Worn out plugs will deffientaly cuz a bog at WOT

i wldnt look at cats as a clogged cat wld be consistent across the whole range .. Normal Cat Temps are usually abt 400 to 450 degree F ... use a laser thermostat to find out. plus if ur cats r out .. ule be running a lil hotter and ur NOX will be enormous (if u have access to a 5 gas analyzer).

now other areas cld include a bad MAF .... take a look at signal ouput .. tho i dont think so ... O2 sensor cld be bad ... theres alot iof things to cause this problem ....

also is the MIL (check engine) on ?????

for me .. i wld start looking at a fuel problem tho .l. check the pumps out first .. start there

~~~ Nissan Driveabilty Tech (at dealership) past 3 yrs ~~~

[rtkota5point9]

Ok, I'm gonna try and answer a few questions.

No cats - so a clogged one is not it.

TPS - When I had my S-AFC hooked up , I put it on TPS monitor and could move all the way from 0.00% to 100.00% with no dead spots.

Speed sensor - I actually explained about my speedo in another thread, but I realize that not everyone reads every thread so I'll just go over it again. The speed sensor itself is fine. I tested it by removing it and hooking it to a drill and connecting my DMM on AC volts and could watch the voltage rise and fall consistently. I then checked the wires from the sensor to the speedo for continuity and shorts, all good there. I could even read the speed sensors voltage from the back of the gauge cluster. But my speedo is bad, and according to the FSM, the wiring travels from the speed sensor to the gauge cluster, THEN to the ECU, so I assume that's why its throwing the speed sesnor code because the signal is getting messed up at the cluster.

CEL - No check engine light, just the code for the speed sensor when put into diagnosic mode.

- I cannot tell if it's fuel or spark - I do believe I noticed a cloud of smoke behind me as it happened one time though.

- It's not a bog at WOT, it's like hitting a brick wall. Next time you're driving your car, hammer on the gas, get the RPMS way up and without pressing the clutch, just let off the throttle all of a sudden. That's exactly what happens.

Now yesterday it happened to me in town, and I could not get the thing going again. I kept hitting the gas, but it just kept coasting. Sometimes it go try to go for a second and then die again and the throttle would be doing nothing. Then it would go for a second, then stop, then go then stop, all with my foot on the same position on the pedal. Finally, after slowing down to literally a crawl, it started moving again normally.

[x0paladin0x]

start looking at ur MAF output then ... a simple scope will depict a waveform from the MAF sensor ...

does the car die or does it still idle .. if so does it idle fine ???

[x0paladin0x]

and as far as ur speed sensors ... those mainly affect ur ABS .. not correlation wif ur driveabilty problem ... unless its an AUTO Trans ???

[rtkota5point9]

When it does it, the motor doesn't actually die. It just idles. And it idles smooth as can be. No surging, high idle, or anything. Just purrs.

It's a 5-spd, not auto.

[x0paladin0x]

start at MAF .. and ur TPS sensors ....

[rtkota5point9]

Will do.

[rtkota5point9]

I know this is an old thread, but I just wanted to let everyone know I figured it out!!



Found that last night. The wire was hanging on by a thread (if that). It's one of the plugs on the TPS sensor. Popped the pins out, re-soldered the wires back onto them, plugged em back in and WHAM! All good now!

No more bogging when I hit the gas rapidly, and no more cut-out at WOT.

Anyone know what this plug does? I mean it has the normal 3-wire plug as well, then this second 2-pin plug??

Whatever it is, it fixed my problem!

[krazyd27]

I've been having this problem for a while now. The picture the OP posted is no longer available and I wanted to know which wire was causing the issue. Does anyone know how to contact 5 he OP?

[NolimitZ32]

Off a 5 year old thread? not likley. Your best bet is to make a thread in the tech section, describe your problem and what testing/troubleshooting you have done in detail and hopefully someone who has run into the same problem will interject.