Misfireing/Fuel Cut at WOT, Need Help

[ghost_22_47]

I've been diagnosing this issue for a LONG time now. Orignally I was thinking it was a sensor or mechanical part (ignitor, coil etc.) Which I have already tested or changed almost everything.
Looking in the timing direction now.
My idle is fine at 20* but when cruiseing it's in the 40*'s and under load it's 21-25* does this sound normal?

Here is one of my build threads
It's a R32 RB26DETT in 1993 240sx Convertible
http://www.240sxforums.com/forums/rb-te ... build.html
It's relitivly except it's running 15psi boost on the stock tune with small changes I made to try and see if anything fixed the WOT issue. I haven't touched timing or fuel I only maxed the TP Load to see if it would fix it and changed the Max Injector Pulse width from 16.5 to 17.5 at 4000rpm+ which changed nothing so I will be changing that back.


From what I'm looking at it looks like the timing jumps and this happens right before everything goes wrong.





I'm not pulling any codes after I fixed the Intake Air Temp Sensor except the light is on for the neutral safty switch.

I will save another log and try and hold the misfire a little longer to get a better reading of what may be going on.

I figured if anyone could help me if this is a Tune issue it'd would be here.

[skylinegtrhr]

except the light is on for the neutral safty switch.
.

So all the time ECU is thinking You are in neutral?

[ghost_22_47]

Probably, how do I turn sensing for this off? I know there is the DTC 1-5 section that has check marks next to certain things but is Checked on and Un-checked off? or is it Vise-versa?

[skylinegtrhr]

It is not some "tree hugers-eco" DTC to turn it off, it is important information for ECU why don't You connect it to switch?

[ghost_22_47]

I'll have to look in to if it's even in the car. It was swapped into my 240sx convertible and I'm not sure it's even there, I can start the car without even pressing the clutch pedal in. Thanks for the heads up.

Curious, about the DTC's though is Checked sensing on and Un-check off? I just want to know because I do have some that 1 is on and the other is off (1 knock sensor checked and the other un-checked) and I want everything right.

[Matt]

turning off DTCs just stops the ECU turning on the Check Engine Light. You need to ensure all your sensors are properly connected or stubbed (resistor for knock sensor for example) to the correct setting

Neutral switch should be at least off otherwise may affect operations like what you are seeing

[ghost_22_47]

turning off DTCs just stops the ECU turning on the Check Engine Light. You need to ensure all your sensors are properly connected or stubbed (resistor for knock sensor for example) to the correct setting

Neutral switch should be at least off otherwise may affect operations like what you are seeing

Ok thank you

[ghost_22_47]

The very first thing that happens is the RHS Bank of injectors cut, with this the TP load also dies and then Bank 2 and TPS drops to Idle Volts and then everything goes out.

The TPS was fine, I stomped the gas and it built boost and sped off and then the Injectors hit this issue and then it all goes down hill from their.



What would cause it to pull perfectly fine until Bank 1 injectors hits past 13.34 MS???

Bad ground? bad signal wire? bad injectors?

This also explains the lean look on the plugs when I pulled them, because one bank was fine and the other looked lean.

Ideas??

[bachig24u]

Looks like your speed signal is missing.

were you loading the car up on the Brakes?

Does anyone know if a TP Limit is used for when the Car is not over a certain speed like 40kms?

what do your TP scales look like?

[ghost_22_47]

It's running on 5 cylinders because it's such a bad misfire. I'll be cheacking coil packs today by swaping one at a time and then driving it to see if it still misses.

Youtube viedo of the car on the dyno with the misfires

http://www.youtube.com/watch?v=ZaJ2TMdcCZo

[Matt]

You have two issues:

Stuck neutral switch
No speed signal

This can make the ECU think you are reving its tits off whilst standstill (ie ECU has no idea that vehicle is actually moving). Would suggest seeing if your speedo works in the dash and if so track the wire from the converter to the ECU pin and fixing that up

Secondly look at the neutral switch on the trans and use a multimeter to check why it isnt activating properly. It may not be as important as the speed signal but worthwhile fixing before further diagnosis

[ghost_22_47]

I will be looking into those but the issue is fixed as of today.

It was cylinder #2 coil pack, replaced it and it runs perfect in WOT.
11A/F @14.5psi boost
I tested the coils resistences but it showed that they were all fine, so I replaced one at a time and drove it after each swap of a coil. Visual ash could be seen on the outside of the coil pack.

[Matt]

Excellent, so that problem is fixed now