Need some Help SR Running Lean

[Rb26kouki]

Not sure if this is the right section to post this up. But any help would be appreciated since I really need my car to get to work.


I have a built S14 SR I'm having problems with getting running right.

To start with Im running

JWT ECU
Z32 Maf
1000id injectors
Nismo FPR
Aeromotive fuel pump
Fuel pressure was set @ 43-44 psi with vacuum hose off when plugged it goes to 35-36psi

My issue is my aem wideband shows 14.7 when I first turn it on after a few seconds it just go super lean falls into the 17s

Service engine engine light flashes a few times then shuts off or sometimes it will remain on until I shut off the engine.

I had this same issue when I used my power FC I had set it up at 42% duty cycle because ID 1000cc actually flow at 880cc & picked VG30 MAF on settings still same issue.

So I thought it was a tuning issue with the basemap on the power fc so I got my JWT ECU flashed for my setup and still same thing.

Anyone ant input on this??

[Kingtal0n]

Well, if you are on 93 octane, my initial guess is that the pulse width at idle is too small for the injector to fully open.

When you first start, there is an enrichment that pushes the pulsewidth up. But once it runs out of that enrichment, you are probably looking at a PW of under 1ms which most injectors will not tolerate.

try increasing the lag time in the PFC until it idles, but when this happens finally, you may find the A/F is in the 12's.

You could try reducing fuel pressure to bring the A/F back. But many cars I have tried this with in the past respond poorly, hit or miss, probably because the injectors spray becomes more of a splurt at low fuel pressures (the fuel may tend to hydrophobic interactions instead of atomize giving the same effect as a carb'd engine with huge ports or sharp corners) which leads to wet cylinder walls, lean misfires, diluted oil, poor performance

So why the huge injector? 1000CC on 93... that should be more than any proper sr20 would ever want.

Guess #2:
clean your maf. Create a boost leak. Yes I said create a boost leak. This will increase maf sensor voltage at the ECU, and walaa more injector on-time. At least you will be able to see if the a/f will stabilize at 14's instead 12's like in my above example. at which point you can point your finger back at the tune, and increase your fuel pressure for the time being.

tell me it drives fine. Also, AEM wideband always starts at 14.7 when it is first started.

[Dboyizmlg]

OP no longer has a PFC.

He mentioned that this set up is with a JWT ECU.
OP did you send the ecu out to JWT for re-flash?

Also if you are breaking in this engine as of it being rebuilt you want to stay on the lean side 14.5-15.3 while cruising, if you running rich you will not allow the rings to seat correctly and possible ruin them. Be aware of that!

Talk to JWT first then, does your engine shut off when it leans out?

[OnTheChip]

An exhaust leak will give you lean AFR readings.

[Rb26kouki]

Well, if you are on 93 octane, my initial guess is that the pulse width at idle is too small for the injector to fully open.

When you first start, there is an enrichment that pushes the pulsewidth up. But once it runs out of that enrichment, you are probably looking at a PW of under 1ms which most injectors will not tolerate.

try increasing the lag time in the PFC until it idles, but when this happens finally, you may find the A/F is in the 12's.

You could try reducing fuel pressure to bring the A/F back. But many cars I have tried this with in the past respond poorly, hit or miss, probably because the injectors spray becomes more of a splurt at low fuel pressures (the fuel may tend to hydrophobic interactions instead of atomize giving the same effect as a carb'd engine with huge ports or sharp corners) which leads to wet cylinder walls, lean misfires, diluted oil, poor performance

So why the huge injector? 1000CC on 93... that should be more than any proper sr20 would ever want.

Guess #2:
clean your maf. Create a boost leak. Yes I said create a boost leak. This will increase maf sensor voltage at the ECU, and walaa more injector on-time. At least you will be able to see if the a/f will stabilize at 14's instead 12's like in my above example. at which point you can point your finger back at the tune, and increase your fuel pressure for the time being.

tell me it drives fine. Also, AEM wideband always starts at 14.7 when it is first started.


Im no Longer using PowerFc

I am now using the JWT ROM Tuned Ecu for 91 Octane

Why such a big injector? Wanted More Headroom as i will be running 2 different turbo setups & i see people running out of injectors at about 410rwhp with 740s on 91

I replaced the Z32 Maf still same problem.

[Rb26kouki]

OP no longer has a PFC.

He mentioned that this set up is with a JWT ECU.
OP did you send the ecu out to JWT for re-flash?

Also if you are breaking in this engine as of it being rebuilt you want to stay on the lean side 14.5-15.3 while cruising, if you running rich you will not allow the rings to seat correctly and possible ruin them. Be aware of that!

Talk to JWT first then, does your engine shut off when it leans out?



Yes i personally took it to them along with my brand new 1000cc iD injectors to have them flow tested which resulted to actually flow at 875cc so thats what they Flashed the ECU For.

Your Right! as i dont want to wash my piston rings! koji had mentioned this to me a while back. So i am aware of that.

i talked to ben he suggested i get a nissan consult cable and plug it to my obd2 code reader connect my computer with ecutalk consult software so i can see everything.

No it doesn't shut off just starts to misfire slightly as i can noticeably tell the engine is not running smooth as i get excessive vibration inside the car.

[Rb26kouki]

An exhaust leak will give you lean AFR readings.

No Exhaust leaks all brand new gaskets along with new hardware.

[Dboyizmlg]

You can try unplugging one injector clip at a time, one by one.
You can determine which cylinder is misfiring, and try the same with coil packs.

Some times it can be a spark plug not gapped correctly, injector O-ring, coil pack.

If it's not one of these, then it might be some thing in the head, maybe a shim oversized leaving the valves open not allowing to get spark. Check your plugs bro.

HMU