stock sr going lean only under acceleration in 4th and 5th

[theredrocket]

Car pulls/boosts fine with correct air/fuel ratio in every gear up to 3rd,
once i get to 4th and accelerate engine goes super lean like 20-21 a/f ratio until
I let off gas, but when just cruising in 4th and 5th a/f stays fine around 14-15.

If anybody has any insight into why this is occuring please enlighten me

[KaminaSan]

Walbro Fuel Pump?
Z32 TT Fuel Filter?
Fuel Pressure reading?

[fliprayzin240sx]

Are you actually using a wideband o2 sensor or is this the christmas tree type gauge that taps off the stock sensor?!?!

[theredrocket]

Yes walbro fuel pump
yes z32 tt fuel filter
fuel pressure is 38psi


and yes its a lc-1 wideband..Im not an idiot, how would I have been able to give you actual numbers if I was using a narrowband

[KaminaSan]

Yes walbro fuel pump
yes z32 tt fuel filter
fuel pressure is 38psi


and yes its a lc-1 wideband..Im not an idiot, how would I have been able to give you actual numbers if I was using a narrowband

You said your fuel pressure is 38psi?

Is that with the FPR hooked up to vacuum, or unhooked?

What is your cruising afrs etc? Care to make a video?

Could be a lazy fuel pump.
Here is the thing though, if you were really hitting 20-21 while boosting WOT, you would be having fuel cut/the car would start jerking and sputtering and backfiring.

Lean Misfiring.

[jr_ss]

Perhaps you should try recalibrating the LC-1...

[theredrocket]

You said your fuel pressure is 38psi?

Is that with the FPR hooked up to vacuum, or unhooked?

What is your cruising afrs etc? Care to make a video?

Could be a lazy fuel pump.
Here is the thing though, if you were really hitting 20-21 while boosting WOT, you would be having fuel cut/the car would start jerking and sputtering and backfiring.

Lean Misfiring.

You are right it is an extreme fuel cut and violent jerk
but I let up right when it happens and try not to boost in 4th and 5th
idk if that is why I haven't heard the backfire but it definetly is getting lean, I'll make a video of the afr when I get out of class.
Well I say 38 that's without vacuum it's suppose to be 43.5 with vacuum right?

But I know for a fact that when I did set external fuel pressure reg I did it to fsm standards.
Thanks for your help im thinking it's gotta be lazy fuel pump now. When it gets lean its like all of a sudden it goes from 14 when I'm cruising in that gear but if I give a little more gas even before it boosts it will jump to 20-21 if I stop accelerating and keep constant pedal goes right back to 14-15.

[theredrocket]

What is your cruising afrs etc? Care to make a video?

Here is a crappy video from my iphone, my good camera's batteries were dead and im about to have to go to work.

Car does symptoms described in 3rd gear in this video.
http://youtu.be/0S666peCjls

Ill make a better video with my stand and camera tomorrow and show u how much easier it does it in 4th and 5th. You really have to get to top of third to make symptoms occur.
In 4th and 5th more so i just barely tap gas and it will go way lean
Sorry for terrible quality.

[KaminaSan]

This could be a few things, as I'm having this issue on my car, when out of boost.

For me, I'll be cruising at 14.5-15 AFR, just very light throttle, and it will randomly jerk, and when it does, my AFR shoots to 18/19.

For me, I was having two issues.
Fuel pump was not working properly. Check your voltage at the pump.
Second, my spark plugs were not right for my setup.

If neither of those work out for you, consider bumping up the fuel pressure, and see if it goes away.

Also, you are saying "If you tap the gas, it goes way lean".

Have you checked out your TPS lately? Make sure it's adjusted correctly. If the TPS is going bad/doesn't read correctly, it can cause the computer to think the throttle is closed, and cut fuel completely.

[theredrocket]

Thanks for the advice, im gonna check those two things. Will update tomorrow

[Kingtal0n]

This could be a few things, as I'm having this issue on my car, when out of boost.

For me, I'll be cruising at 14.5-15 AFR, just very light throttle, and it will randomly jerk, and when it does, my AFR shoots to 18/19.


This is a misfire situation in which the air/fuel goes LEAN because its reading all of the unreacted oxygen in the exhaust system. A wideband gauge only works effectivelly when there are no complete misfires. that said, a partial misifre, such as a cylinder event that only combusts 80% of the air/fuel available due to a weak spark or too small of a gap, what happens to that other 20% of unburnt fuel/oxygen? That is where an EGT gauge complements the Wideband. Unburnt fuel entering the exhaust with unburnt oxygen may burn in the manifold and artificially raise the EGT and cause a glowing manifold, A situation similar to retarded ignition timing.


once i get to 4th and accelerate engine goes super lean like 20-21 a/f ratio until
I let off gas, but when just cruising in 4th and 5th a/f stays fine around 14-15.


As was mentioned already, this is likely a fuel pump/pressure issue. Your fuel pressure DURING 15psi of boost should be well over 50psi. And using the right plugs, on an OEM turbocharger I recommend OEM plugs, with the OEM gap or larger. The more gap you can get away with the better, but too big and the spark cannot make the jump, so there is a fine line between gap and resistance at the tip. If you have plenty of fuel volume(verified good fuel pump), and plenty of pressure (verified regulator set correctly), some other possibilities: (computer, maf, injectors, low voltage, wideband calibration, malfunctioning sensor, pre-turbocharger vacuum leak, I will think so more ...

[Kingtal0n]

I just watched the video and nothing abnormal happened. Are you talking about the gauge reading 20:1 when you let off? that is normal, the engine stops injecting fuel when you lift from the gas pedal, so the wideband reads ultimate lean (generally 20:1)

If you are noticing the sensor reads numerically higher than 12:0 during WIDE OPEN THROTTLE then that is a problem. And yours seemed to "lag" a bit, around 13.5:1 before dropping to 11.8, but that is also somewhat normal, I have seen it before but I would not tune it that way myself. Just make sure that once the sensor reads around 12:1, that it does not RISE AGAIN during WIDE OPEN THROTTLE. It needs to hit 12:1 and STAY THERE during the entire wide open throttle run.

Anytime you LIFT from the gas pedal, the wideband should shoot right to 20:1, indicating that fuel has stopped injecting into the engine.

[theredrocket]

I just watched the video and nothing abnormal happened. Are you talking about the gauge reading 20:1 when you let off? that is normal, the engine stops injecting fuel when you lift from the gas pedal, so the wideband reads ultimate lean (generally 20:1)

If you are noticing the sensor reads numerically higher than 12:0 during WIDE OPEN THROTTLE then that is a problem. And yours seemed to "lag" a bit, around 13.5:1 before dropping to 11.8, but that is also somewhat normal, I have seen it before but I would not tune it that way myself. Just make sure that once the sensor reads around 12:1, that it does not RISE AGAIN during WIDE OPEN THROTTLE. It needs to hit 12:1 and STAY THERE during the entire wide open throttle run.

Anytime you LIFT from the gas pedal, the wideband should shoot right to 20:1, indicating that fuel has stopped injecting into the engine.

Well since the video doesn't show my feet, u can't tell I'm not letting up on the gas before it shoots to 20
I experience a harsh jerk an fuel cut I'm guessing. I'll try to make a better one tomorrow after I play with my fuel and spark,
haven't had much time to work on the car lately.

And haha yes I know that when u let off throttle the air/fuel
will jump to 20.
I'm having another problem with my clutch it keeps overextending slave cylinders ,
The clutch fork arm is having to be pushed to far before the clutch engages. And then does not come back down with enough force to push slave back in allowing slave to just push rod to far out blowing seals and leaking.

[steve shadows]

What EMS or ECU are you using?

It sounds like the car just needs to be properly tuned. 4th and 5th gears put the most load on your motor so if your fuel pump or fuel system is not 100% up to feed the motor then these are going to be the gears where the car leans out the most when driving or popping in and out of load.

[theredrocket]

Yea im an idiot haha it was because the speedometer which isnt even wired into speed sensor in transmission was hitting 120 , so speed limiter just shut it down in those various gears. Figured it out a while ago just thought I should give this thread some closure. I don't know why but when i got wiring harness from wiring specialities the speed sensor connectors didn't match up. Should I just solder the wires together color matched?

[theredrocket]

Can a mod delete this thread fixed the problem

[Chay G]

You are right it is an extreme fuel cut and violent jerk
but I let up right when it happens and try not to boost in 4th and 5th
idk if that is why I haven't heard the backfire but it definetly is getting lean, I'll make a video of the afr when I get out of class.
Well I say 38 that's without vacuum it's suppose to be 43.5 with vacuum right?

But I know for a fact that when I did set external fuel pressure reg I did it to fsm standards.
Thanks for your help im thinking it's gotta be lazy fuel pump now. When it gets lean its like all of a sudden it goes from 14 when I'm cruising in that gear but if I give a little more gas even before it boosts it will jump to 20-21 if I stop accelerating and keep constant pedal goes right back to 14-15.

that just happened to me, i was blaming my mines ecu, but after blowing 2 water hoses i found out that i need a new head gasket!

[theredrocket]

that just happened to me, i was blaming my mines ecu, but after blowing 2 water hoses i found out that i need a new head gasket!

yeah mine was even easier fix never noticed it until after i posted but everytime it cut off it was when incorrect speedo reading said 120 because it was reading from a s13 speed sensor an i have a s14 so put in my s14 ka speed sensor an works like a champ.. Should of realized that earlier since i use to run a tuned ecu that had speed limiter removed therefore I never worried about fixing speed sensor..