KA24DE Running SERIOUSLY Lean

[rsmithdrift]

Ok so I've had some issues with this car for a while. I've done alot trying to chase this grimlin down. Some of you may remember some of my past threads about it's problems (all related)

Well, I have since then installed an SAFC II and a A/F Gauge to try to solve the cars severe leaning issue. With the factory tune the gauge never leaves the max lean position. It usually goes so lean that it goes off the charts and beyond the gauges measurable range. So to correct this I have to turn up the correction on the SAFC. To get the idle into the stoichiometric range I have to turn up the 800rpm or less to +25%. For it to stay stoich at low throttle I have to keep it +25% till 2500rpm at which point it has to increase to +30% untill 4000-4400rpm at which point it has to drop back down to +10%. And at WOT it runs max lean NO MATTER WHAT. I have it set to +35% at above half throttle from 1,000rpm all the way to 4,000rpm then +15% to redline. It still says max lean from 4k rpm to redline but if you add fuel it just looses power. The other strange thing is that the a/f gauge seems to jump constantly from max lean to stoich/rich while cruising. It's like the O2 signal is cutting in/out constantly at low throttle. But at idle it stays steady at stoich. and at mid/high throttle it stays steady at max lean.

Anyways, here's the stuff I've replaced/done to the car and everything you need to know about it. I've got a short ram intake (new filter) I've removed the vacuum system. Only vac lines are the FPR and Brake Booster. I've replaced the intake mani gasket. So I KNOW it has no air leaks anywhere. I've replaced the coil, the cap and rotor, the wires, and the plugs get replaced/repaired constantly. The spark seems a little weak on cylinders 2 and 3 for some reason. I don't think it's enough to cause a problem though. So we can rule out ignition system. I set the timing as needed by the way. (I think it's at 18* right now.) Anyways I've replaced the fuel filter with a 300zxTT one, and I've replaced the entire fuel rail with a known good one. So the injectors and FPR are in good condition. As for the fuel pump it works but I've never actually tested it for pressure. I have no way of doing this. The CTS reads the exact values the FSM says it should. The MAF reads the exact values the FSM says it should. The knock sensor works perfectly as per FSM. The TPS works perfectly as per FSM. The O2 sensor works perfectly as per FSM.

So honestly I have no freaking clue what could be causing this. It seems to run fine above 4k rpm it just runs lean as f_(% untill then. So if you have any ideas please tell me cause I'm just lost.
Modified by rsmithdrift at 8:29 PM 12/23/2009

[KATwo40]

Are you using a wideband or narrowband O2 gauge?

[r3v_v3ng3]

yeah sounds like your using a narrowband gauge

[rsmithdrift]

Good ole single wire Bosch OEM replacement O2 sensor.

I'm pretty sure it still reads correctly because it cuts out like a MF'er at factory tune and when the thing reads dead lean all the way.

[rioredstang]

I think you have to have a fuel pressure gauge installed to moniter fuel pressure. You may be covering up for another problem. I would also put a new o2 sensor on and backprobe sensor return with a ohm meter. Now you can watch fuel pressure and o2 sensor to see if they agree with safc. I would watch my maf sensor readings to see where they go.

[liquid_cool]

id go a few different ways here...replacin'n the O2 sensor is a no brainer...but id allso look into the peul pressure regulator and upgrade the injectors..just to be on the safe side..

btw...how long have you run her lean like this?...if its been for a few weeks or even a month..i bet that the head looks like swiss cheese now due to detonation rite around where the head meets the cylinder wall on the exauhst side...(head) side....fuel pressure gauge is a must bro...there 30 bucks for a good one.

good luck

[rsmithdrift]

id go a few different ways here...replacin'n the O2 sensor is a no brainer...but id allso look into the peul pressure regulator and upgrade the injectors..just to be on the safe side..

btw...how long have you run her lean like this?...if its been for a few weeks or even a month..i bet that the head looks like swiss cheese now due to detonation rite around where the head meets the cylinder wall on the exauhst side...(head) side....fuel pressure gauge is a must bro...there 30 bucks for a good one.

good luck

Dude it's been running like that off and on for the past 2 years. For a while I had a MAF that was known as BAD that would fix the problem by making the car run so rich it was insane. I'm talking blowing black smoke and reading 10v at idle. But It's run lean for maybe 6 months total being driven every day.

But with the car tuned right on the SAFC it runs perfect and makes so much power it'll light em up into second gear no problem. I mean it pulls hard. I timed it at just shy of 6 seconds to 60 with a good launch and on flat ground. From what I can tell that's better than it should be doing from the factory. So their can't be too much wrong with the internals.

[rioredstang]

Hey man, are you in Chattanooga or FL. I'm in Chatt.

[rsmithdrift]

Hey man, are you in Chattanooga or FL. I'm in Chatt.

Chatt town atm

[rioredstang]

You should drop by my shop and we can check out your problems.

[jeff420]

ummm. am i the only one who sees a problem?.....your using a narrowband gauge.........its very innaccurate. i think you need to do some research........ if your seriously worried about your car runnin lean, take it to a dyno and have it hooked up to a wideband. or at least for the love of god get a real o2 gauge. i had one of those narrowband gauges in my car when i bought it, made such a cute little light show, but thats about all it did.

[rsmithdrift]

Well I just put the gauge in their when I put the SAFC in two weeks ago.

I tune the safc to wherever it runs right and aside from the bouncing it does seem to read stoich when it runs right and lean when it's cutting out and rich when it smells rich.

I don't think the 02 is the problem. It's the one the car was designed to run with and it's had this problem for a LONG time now.

But i agree a wideband would be more accurate

[liquid_cool]

if you have had this issue for a few years...get ready for some serious head work when you do your next headgasket...and ya he's rite...if your playing with the fine tuning...fuel,timing to get more power....you MUST get a wideband....so far..your rods have held up...but who knows when you run just lean enough to blow sumpin throu the block bro.....run it rich for now..to be on the safe side..just enough to smell it from the exauhst...and retune once you get a good wideband to do it with..good luck.

[jeff420]

how do you know its running lean besides just guessing?

i dunno i have an xcessive intake manifold, header, 3" catback and stage 2 cams on my ka and never felt that it was running lean.

[KATwo40]

Ok...am I correct in understanding this is a stock KA setup? No forced induction, spray, etc?

If I'm correct, please follow my instructions below. I don't mean any of it to be rude...but I do know what I'm talkin' about.

Step 1: Understand how a narrowband O2 sensor works. The sensor is designed to "bounce" between full lean and rich when the engine is at idle or part throttle cruise. The ECCS uses this to find an average, and consequently alters the fuel mixture to reach the average stoich burn based on the "bouncing" of the O2 sensor.

Step 2: Remove the narrowband O2 gauge from your car. Toss it in the garbage.

Step 3: Remove the SAFC from your car.

Step 4: Drive it like you stole it and forget about it.

From the factory, the ECCS is calibrated to be a little on the rich side under WOT dyno pulls. However, keep in mind, they're counting on someone using the crappiest gas they can find.

Seriously, best thing you can do is drop the issue and drive the car. You'll enjoy it much more.

[rsmithdrift]

FYI I fixed my cars problems and the fuel pump was bad. Making 15psi peak. That's a long ways away from 44psi. It's a wonder it ever ran at all.