Hit Gas Pedal Nothing Happens

[BrianV8]

Hey guys i'm a little stumped here because this is an issue that comes and goes and last night it almost left me stranded.

Basically once in a while something happens that the car will idle but if your driving and hit the gas it will not recieve any fuel until about 20% throttle. Last night for the first time i got really bad and hitting the gas had no effect at all.

Its an rb25 swap i did with a z32 mass air. From day one i had some problems with the tps, i diagnosed the hell out of it and completely unplugging the tps the car will still run and rev fine. Like you would expect, motor gets more air it revs up. I could not duplicate the problem.

So my next guess was mass air, unplug it, car dies. So would this be a problem with the mass air sensor itself or is it a problem a wire going to it?

Thanks Brian

[FunnyGas]

Pop your hood...

Under there you will find something attached to your transmission... its a little nuisance.. Nissan designed it for the wealthy and patient... its called an RB

[Skym]

Sounds like TPS failure due to it prevents a lean condition / hesitation when suddenly opening throttle body (hence why it's mounted on throttlebody). Sometimes TPS is not fixable and requires replacing. I've been through 2x TPS on my car already, one lasting around 30,000km or so (depends on how you drive car which affects how long TPS last's). Tried temporary fix by pulling it apart, playing with (bending) idle, WOT pins. It sort of worked but TPS was stuffed (circuit board part). Use, dispose type of sensor. I was thinking if a optical TPS sensor from a Toyota would work, but don't know if it's compatible with stock ECU.

If have aftermarket ECU, removing MAF plug can make engine stall. With stock ECU you have to unplug MAF before switching engine on to check as it uses a default value / voltage.

[hozer]

Hey guys i'm a little stumped here because this is an issue that comes and goes and last night it almost left me stranded.

Basically once in a while something happens that the car will idle but if your driving and hit the gas it will not recieve any fuel until about 20% throttle. Last night for the first time i got really bad and hitting the gas had no effect at all.

Its an rb25 swap i did with a z32 mass air. From day one i had some problems with the tps, i diagnosed the hell out of it and completely unplugging the tps the car will still run and rev fine. Like you would expect, motor gets more air it revs up. I could not duplicate the problem.

So my next guess was mass air, unplug it, car dies. So would this be a problem with the mass air sensor itself or is it a problem a wire going to it?

Thanks Brian

Had this exact problem on an RB26. Was at first a bunk TPS reporting incorrect values, was reporting 0 until around 20% throttle as well right around 3000rpm. After replacing the TPS the problem improved and would come and go intermittently. After many painful hours and lots of swear words, turns out the wire to the ecu was not all the way "plugged in". Trace your TPS wires and make sure they are okay, then reset the TPS "pedal throw" then see if your problem still happens.

[Skym]

Good advice ^^^^.

[BrianV8]

ya i figured tps, i have 3 kicking around and all three at some point had this issue, when i installed the motor we had a ground wire break, so we rewired the plug that comes off that little harness back to the ecu. I played with those wires with little luck bringing it back.

The other symptom when its doing that is when i'm just sitting i rev the engine and within that 20% it won't rev past 2500, it hits 2500 and drops to 1000 and tries again over and over. It was also idle hunting bad during this time. These all syptoms of tps?

[hozer]

ya i figured tps, i have 3 kicking around and all three at some point had this issue, when i installed the motor we had a ground wire break, so we rewired the plug that comes off that little harness back to the ecu. I played with those wires with little luck bringing it back.

The other symptom when its doing that is when i'm just sitting i rev the engine and within that 20% it won't rev past 2500, it hits 2500 and drops to 1000 and tries again over and over. It was also idle hunting bad during this time. These all syptoms of tps?

Yup... driving along and it starts chunking like you don't know how to drive a stick? If so that is a TPS issue reporting bad values, or none at all. Generally caused by bad voltage to the unit (for RB26 3<voltage<1 caused issues for me... heavily modded though)
Hunting idle is not normally TPS issue, however given your symptoms I would say they are linked. Probably a bad calibration i.e. TPS reads 10% throttle at no pedal and cause mad idle hunt cause ECU doesn't know WTF is up

[BrianV8]

ahh ic, Just amazes me from day 1 with this motor this has been nothing but a hassel,

So to confirm the harness that plugs into the body of the tps is the idle activation,

the 3 wire harness comes off the tps is my power ground and signal correct?

Thanks Brian

[hozer]

ahh ic, Just amazes me from day 1 with this motor this has been nothing but a hassel,

So to confirm the harness that plugs into the body of the tps is the idle activation,

the 3 wire harness comes off the tps is my power ground and signal correct?

Thanks Brian

Unable to confirm this, I have full stand alone on RB26... I imagine its different

[Skym]

MAF could be the cause of 2500rpm rev limiter if using stock ECU.

[BrianV8]

i confirmed the wiring, one last question, what does the tps cross over to anything, Like can i go buy a new one at a local autoparts store? 300zx or something?

[BrianV8]

not really a rev limit more of a hesitation, more than the 20% throttle will make it go beyond

[hozer]

was specific for the 26

[BrianV8]

Alright so i did a bunch of diagnostic over my lunch break. All the wires going to the ecu are good, moved them around etc never lost contact, Continuity always there. I tested the sensor further seems to be perfectly fine. But i can't see the wiring coming and going like it has so i am assuming i have another bum sensor. I threw a spare i had on there but don't know if its any better but once again its working for fine for now.

So i am assuming here best next step is a new sensor? Can i purchase these new? From where?

Thanks Brian

[Skym]

Don't know what it crosses over with. The Toyota TPS is supposedly better due to being optical. Can fit a Motec M660 ECU and run fly by wire setup. As far as I know, most new Nissan's run fly by wire.

Just fit a new TPS sensor from Nissan. TPS should be changed out every time you change narrowband o2 sensor (routine maintenance) which is around 40,000km-60,000km. That's if you drive normally. If thrashing car, alot earlier.