Slight throttle running lean

[JacobT]

Stock S14 SR running 10psi and full 3" exhaust, a walbro 190 fuel pump and brand new 300zx fuel filter.

Under slight throttle the car runs stupid lean. Like 15.5-16s AFR. The car will build a bit of boost but wont move until it starts to reach the higher RPMs. When I push in the clutch the car sometimes wants to die/does die and tends to idle on the lower side. Did a boost leak test, couldn't hear/see anything leaking. I don't know what is causing this lean condition. Spark plugs look normal.

Any ideas? o2 sensor?

[s13 drifta]

I am dealing with the same problem right now. Even on slight throttle my a/f ratios jump up to 16-17, when I give it WOT it will bog and hesitate.
I have tried cleaning my MAF, new coolant temp sensor, checked timing, new plugs (bkr7eix-11), new fuel filter, tried a stock wastgate, new intercooler, new coulpers and clamps, no boost leaks, and my fuel pressure is at 40psi and climbs with throttle. Im going to try a new maf and see if that changes anything. Its getting rediculous and Im running out of ideas.

[steve shadows]

Stock S14 SR running 10psi and full 3" exhaust, a walbro 190 fuel pump and brand new 300zx fuel filter.

Under slight throttle the car runs stupid lean. Like 15.5-16s AFR. The car will build a bit of boost but wont move until it starts to reach the higher RPMs. When I push in the clutch the car sometimes wants to die/does die and tends to idle on the lower side. Did a boost leak test, couldn't hear/see anything leaking. I don't know what is causing this lean condition. Spark plugs look normal.

Any ideas? o2 sensor?


What is your Fuel Pressure like?

Check it at idle, I suggest running at least 38-42 psi with the vacuum hooked up

[Hashiriya415]

unplug the o2, it's gonna run rich by default.

[JacobT]

unplug the o2, it's gonna run rich by default.

I did this and the car ran leaner all the time?

[jspaeth]

IF you guys are on stock ECU, I am not sure what to tell you.

If you are on a standalone, you can alter injection values based upon rate at which the throttle is being depressed.

...I know this because conincidentally, I was just reading about this for like 4 hours on the RX-7 PowerFC forums....it is a common issue to lean out when you rapidly tap the gas pedal

[s13 drifta]

Im running a stock ecu, I think my problem is in my wiring. I just bought a brand new harness, so I will let you know how it works and if it fixes my problem.

[fullthrottle]

Flow test injectors? Swap MAF with a friends good running car? These are the things I would try.

[Hashiriya415]

When you unplug it, the ECM runs rich by default. Could it be that your o2 wire is spliced somewhere and now your ECM sees over the 500mv so it leans the mixture.