abaron13

I got my new swap in and running but it's running way too lean at all times. It seems like the fuel map is off or something. The maf is fine, no boost/vacuum leaks, fuel pressure is perfect and it has a brand new fuel pump. What could be the reason for it running so lean besides a bad ecu?

pacotaco345

Have you checked fuel pressure? If you have an exhaust leak before the o2 sensor that can cause it too

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abaron13

Fuel pressure is good, as previously stated. No exhaust leaks either


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ka-t

all stock ?

abaron13

Other than a fmic it's all stock, yes.


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bmxer882x

Are u missing really bad? Like one cylinder isn't getting fuel? Or is it even like all cylinders are being starved? If it's just one check your injectors. (To test pull off a coil from each cylinder when the cylinder gets no change in idle your problem is in that one)

abaron13

No the car runs and idles fine, I can't figure out what's up with it.


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bmxer882x

If it runs and idles fine I would say u have an exhaust leak. Recheck all your fittings before your wideband. Also check it's completely screwed in and tight.

abaron13

I triple checked that. It smells like it's running lean, and it hesitates under certain loads while driving.

abaron13

It's throwing me for a loop because I've already checked every logical thing it could be, other than swapping in another ecu, mainly because I can't find one anywhere...

I posted here as a last resort to see if I missed something stupid.

801nismo104

do you have a wideband or are you just guessing its lean?

abaron13

I have an aem wideband

bmxer882x

Only other thing I could think of is check and make sure ur ecu doesn't have a room tune in it. Or check to see that you are getting a solid 12 volts at the injectors. Iirc mine was 12.36 volts.

abaron13

That was the first thing I checked when I got the swap, no rom tune. That should make it run rich instead of lean anyways, I would think. I'll look at the voltage


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abaron13

The ecu is throwing a code for the maf, but the maf and maf wiring is fine. I'm also getting good voltage at the ecu (1.4v at idle)


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jaxshawn

did you get the swap as a full set up, s13/14 sr20's use 370cc injectors but the s15 uses 434cc (400 something not sure on exact)

abaron13

480cc and yes I have the full swap


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jaxshawn

adjustable fpr or stock?

and what was youe fuel pressure at idle

abaron13

Stock 43psi


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jaxshawn

did you calibrate your wideband before installing it?

abaron13

Aem widebands dont require calibration. However it is on the right setting.


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oni jake

The MAF sensor code could mean anything involving air flow. You have a boost leak somewhere if you're absolutely sure everything else is fine.

Tom N

How do you know for sure the maf is good?

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98 240sx w/ S15 SR20DET, T2 20g, 11.22 @ 124.98

bmxer882x

Just off of memory there is two different injector sizes. The 480 in the type r and the 444 (I think). The 480 came with the db turbo where as the other was in the automatics with a t28 journal bearing. I'm not sure but there should be two different ecu's. Do some searching and make sure u have the right injector/ecu combo. Sorry for not knowing exactly just trying to point u in a direction to look.

oni jake

All OEM manual S15 ECUs are tuned the same way; injectors are the same across the board for every stock S15 turbo motor out there.

EDIT: When ECUs go out, they don't make A/F ratio mistakes. If something were to happen, the ECU goes into LIMP mode if possible. If not possible, the ECU will shut down all together. Your problem has nothing to do with the ECU

abaron13

Ok I had the injectors cleaned and flow tested. They're fine. Good fuel pressure. The entire fuel system itself is fine. I have no boost leaks. And there are also no exhaust leaks pre wideband. What else could it be other than the ecu not telling the injectors to dump enough fuel?

Tom N

What fuel pump? Have you checked voltage at the pump?

Are you positive you have a good working S15 maf?

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98 240sx w/ S15 SR20DET, T2 20g, 11.22 @ 124.98

abaron13

It's a brand new dw 220 and the voltage is good. I questioned my maf so I bought a known working maf and it did the same thing. The voltages to and from the maf are good as well.

Tom N

Ecu could have a non stock tune on the chips.

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98 240sx w/ S15 SR20DET, T2 20g, 11.22 @ 124.98

abaron13

I cracked it open as soon as I got it, there's no daughter board.