S14 w/ S14 SR worked fine then FUEL CUT at 2000rpm

[alesserfate]

Hey folks,

My daily is a 1995 s14 240sx with a kouki s14 sr20det (blacktop, vvt).

I've been driving it for a while now and then one day it cut fuel for a split second when I was on the freeway as if I hit speed cut, but then came back a few seconds later.

Then oddly enough it started doing it more often, and now it's doing it pretty much all the time after a few minutes of starting the car. It idles fine does not stutter or anything of that sort, no black smoke out the exhaust either.

What happens is when you get on the throttle, it revs to 2000rpm and then cuts fuel, drops, and then you can continue doing that, aka hitting the rev limiter kind of deal at 2000rpm.

I was thinking bad sensor somewhere ? I've checked my maf wiring and checked for damage on the wiring harness in various places I could think of.

Any ideas what this might be ?

[Killa_D]

maybe a bad maf sensor

[alesserfate]

Ok so today I spent the day trying to fix it, still not fixed, heres what I checked.

- tried different MAFS, checked all maf wiring and connections
- checked ecu connectors/wires and the M63 connection
- checked wheel wells for rubber through harness and checked ignitor harness in the engine bay
- checked the TPS, works fine
- switched ecu's, same thing

Now, the problem GOES AWAY, COMES BACK, GOES AWAY, even WHEN THE CAR IS JUST SITTING THERE IDLING

However when I'm driving, say I'm doing 3000rpm in 4th and it cuts away, i clutch in, put it into 2nd, and release the clutch, the momentum of the car takes it past 2000rpm, and then if i floor it, it breaks the 2000rpm barrier again for a little while.

Any input ? I was thinking bad ignitor ?

[4x4le]

Thats not a bad ignitor btw

It could be an ecu problem. Its screaming maf, but if you checked that and replaced it..........


I always recommend people get a consult cable and nissan datascan when dealing with cars like ours. Watching the readout and being able to datalog the readouts of all the sensors is so helpfull it isnt funny! Im sure you will be able to see exactly whats wrong, just make it happen while watching the laptop.

[alesserfate]

thanks for the help

unfortunately my consult plug isn't wired up at the m63 so its useless

going to keep playing around with it today, maybe I'll find something, but keep the tips coming please!

[4x4le]

http://i300.photobucket.com/albums/nn40/4x4le/ecu%20pinouts/consult_pinout.jpg
I dont seem to have a s14 sr ecu pinout, thought i had one, but anyways as you can tell they are easy as heck to wire in if you know which wire is which.

[alesserfate]

all the sensors are working properly.. but problem still persists, was ok for about 6 hours of the day, then failed again

im starting to think a wire in the engine harness has a rip somewhere, the question is just... which wire. can't multimeter trace it since its so intermittent

[4x4le]

http://i300.photobucket.com/albums/nn40/4x4le/ecu%20pinouts/ECUS14ZSR20DET.jpg


Boom, here is the s14 sr ecu pinout I was lacking. Now wire in your consult port properly, get a consult cable, and get nissan datascan and datalog. As soon as the problem occurs pull off to the side of the road and look at your log. You will see a sensor act funny and then diagnose that wire/sensor.

I dont know what anyone can tell you other than that man.

[alesserfate]

Thanks alot for your help.

I'm going to get my hands on these items and get at it.

[95KA-Turbo]

This sounds similar to what I was going through, and from what it sounds like you've already found my old thread since you say you've checked the actual wiring for your MAF.

You can check your wiring by using the ECU pin out to check for continuity through out the wiring harness....but it is a huge pain in the ass. You have to unplug your sensors (I'd just start with the MAF) put one of the multimeter pins in the MAF wire and the other one on the ECU plug in the corresponding spot and check for continuity, if you don't have it then you need to go through and replace that entire wire.


I hope that makes sense. Have you checked to make sure your 'F' plug isn't loose and all of your wiring you did for the swap is still intact and not loose or anything? Another easy thing you can do is the "jiggle test" were you just start the car and shake the crap out of everything (by everything I mean the harness or the wires going to a particular sensor) until you hear the motor change/the problem occurs. It's basically a loose connection test and saves time unwrapping every wire...although it isn't as 100% guaranteed to find the problem (assuming it's a loose wire) like unwrapping the connections.