SR20 runs lean at idle only.

[JesterX18]

So I finally have my SR20 running. I have an aem wideband where I base all my readings. The car's AF ratio is 12.0 under boost, around 14.7 cruising, and of the charts lean at idle. The funny thing is that on a cold start is sits perfect at 800 rpm and 14.7 AF for about 5 seconds then climbs off the charts and starts to misfire slightly. At first the exhaust smelled rich to me and I thought my gauge was wrong, but after unplugging MAF it idled smoother and the AF was around 10 then it smelled rich. So my set up is a typical GT2871r,Z32 MAF, 810 DW injectors all controlled by a Jim Wolfe Ecu. I have tried seemingly everything including another Ecu(same tune) still runs lean. Datascan isn't showing me the problem either. Searched this problem for weeks and no one ever solves it. Anyone got an idea?

[JesterX18]

So I've been switching ECU's back and forth and seemed to have it idling around 15.7 with my friends ECU. Its not misfiring and comes down to idle perfect. What I notice is that my lean condition is in direct relation with my o2 sensor reading via datascan. when the o2 reads 87 at idle its running good. if I blip the throttle the o2 reads 0 for ten seconds or so and then goes back to reading 87. While it reads 0 the AF ratio is lean on the wideband. While driving the o2 switches back and forth normally. When I plug my ECU in the o2 always reads 0 at idle and wont change unless I drive it and accelrate. And my wideband is constanlty lean at idle. Also it stumbles coming down from decel. So then I decided to unplug it. The o2 sensor now reads 32 and still runs like crap. So all ive done is switch ECU's and at least when its warm the problem seems to be gone, except when the o2 reads 0 after I rev it. So it seems this ECU is bad. Another thing to note is my ECU is tuned fro 720cc injectors as that's what they flow tested at wolfes and my friends for 810cc. so my friends ECU tends to run leaner across the board. 14.1 AFR in boost in my car. I have read the o2 reading should be zero at idle.... is this true?

[OnTheChip]

All of your issues are readily solvable with a realtime tunable ECU like theNismotronicSA (http://www.nismotronic.com/product_info.php?cPath=22&products_id=29) system, which among it's many stand-alone type features, includes the ability to switch to speed-density tuning using a MAP sensor instead of MAF.

[JesterX18]

Update, Well I've been messing with this issue all week and I've learned that the car runs lean at idle almost all the time with both ECU's so I'm fairly certain it isn't them. (one wolfe, one enthalpy) I took apart the IACV and tested it today. had 9.5 ohm on AAC and 20 ohms on the other valve. Both actuate propery when powered. I have power to them and they are now clean as can be. No change though. o2 has 12 volt power, ground, and signal stayed between 49 and 53 mv with the AFR just over 18. Going to unplug MAF tomorrow and measure the voltage again. It didn't change much when I revved it a idle though.(its also brand new) one the firewall side of fusebox I only have the middle plug installed. Is that the only one required? there's a grey socket and brown socket also. wondering because another Zilvian had the same issue and his happened to be a wrongly pinned brown connector for
o2 and IACV. Any ideas? Anyone?

[ultimateirving]

Possible you have an exhaust leak before the o2

[Kingtal0n]

You have a rom tune so there is a good chance your problem cannot be "fixed" without altering the tune... which you cannot do...

My suggestion is this,
Get the car to DRIVE perfectly fine. Fix everything about the way it drives (by altering fuel pressure / maf sensor / injectors / etc...)

THEN worry about the idle. Use a SAFC-2 to dial in the idle air/fuel ratio as desired.
Do not use the SAFC to dial in anything except idle fuel and it will work fine.

-keep in mind any air leaks, and old maf hot-wires (is the maf filthy or old?), will also lead to this issue you have.
-So will an exhaust leak (O2 reads lean at idle because of exhaust leaks).
-so will improper O2 wiring / bad O2 sensor

[JesterX18]

Nah no exhaust leaks. It's not a false lean reading. The car drives awesome as long as your moving... I shouldn't have to use a safc to run my car at idle but I appreciate the suggestion. And it runs lean at cold start too, so o2 wouldn't be the whole issue. I tested Maf before and it tested good. And the voltage is in spec on the consult, but yeah your right I've read that a Maf did that before. I've replace mine already.( unless I got 2 bad mafs and the reference voltage it generates doesn't mean squat. It's really strange, idles good for a few seconds the duty cycle of the injectors goes down and the AF ratio goes up. Something is causing it. I would say it's the program in the ecu, but it does run right for ten seconds or so. Then after the idle will come down and it will stall if I don't blip the throttle, does that for a while and once warm will run at a shaky 800 ish. Coming down from a rev or stopping and idling it falls down to 500 before slowly recovering. The o2 never reads at idle on the Wolfe ecu. Regardless it should still have a decent cold start. But you definitely made some key suggestions. Sent some ecu comparison data logs to Wolfe and they are in review atm. Hopefully they see something...

[Kingtal0n]

There are only 2 major arteries for fuel flow.

One is electronic, the other is liquid/pressure

If your ecu / programming / wiring / electronics are not at fault (which is actually quantity of electron unit being counted),

then by process of elimination, that only leaves,

fuel pressure, flow, injectors, physical obstruction, physics, gravity, air pockets, temperature, etc... (physical quantity unit)

Short:
If your fuel system is fine, and your electronics are reading/working properly, then you must have the wrong weight fuel in your gas tank (because those are the only two possibilities). Unless I am grossly oversight something obvious.


To verify your engine / wiring, I would re-install OEM injectors / maf / ECU and verify the engine runs normal.
IF it does the same symptom, you have narrowed it down to sensors / fuel system / wiring that sort of thing.

[JesterX18]

Yeah I agree with everything you said. I've been fortunate enough to get it to idle right for a short time and there is a significant difference in injector duty cycle. so id like to find out what is causing the difference. Bad sensor input, bad ecu, bad tune. That why I swapped ECU's. But yeah I tired swapping it all back minus the turbo just to see how it idled but unfortunately the spare ECU I was given with my second swap is a J4. Only fires one cylinder in my car. So yeah I'm gonna buy another ECU as soon as wolfe gets back to me with his conclusion. I just have to think its something ridiculous in the ECU at this point or some very freak wiring incident with my wiring specialties harness. Was kinda hoping somebody had a magical answer that was just crazy enough to work with what I already have. This isn't a run of the mill concern based on what I've searched. Thanks for your input!

[OnTheChip]

Sounds like it could be a vacuum leak, which could be coming from the BOV, even if recirculated.

[TCory1]

I have been battling a lean idle condition for a while now. I have actually discovered that my injectors, 3 & 4 are not seated properly. Seated MAF sensor cleaner where they all seat at the intake. When sprayed, injectors 3 & 4 made a noticeable change to the idle. Well need to replace injectors bushings and or go back to OEM fuel rail, haven't decided yet. Running a Circuit Sports rail now. Or rid the ISR intake. I'll advise of the results.