Fresh ka-t running lean...o2 not reading?

Basic tech questions such as future setups, different turbo kits, car diagnosis, etc
Post Reply
mt2forty
Driving Mom's Station Wagon
Posts: 28
Joined: Sat Jun 02, 2012 3:12 pm

Fresh ka-t running lean...o2 not reading?

Post by mt2forty » Sun Mar 24, 2013 4:56 pm

My wideband is reading 16.9ish at cold idle and 18+ (off the gauge) once it warms up.

Consult is showing great signals for everything except the o2 sensor, which is steady at 0v. I have tried a couple new o2 sensors and have double-checked the harness wiring, which has beautiful continuity. Is it likely that this is the root of the lean issue? Likely the tune (enthalpy)?

Boost leak test was great - holds 20psi no problem. Vacuum is steady at 20hg and I've checked everywhere for the last 2 months for additional leaks.

MAF voltage is great and linear with throttle. TPS is new and voltage is set to 0.45v at idle and approx 4v at WOT.

Fuel pressure (as read by my adj fpr) is great. Injectors were cleaned and flowed.

Idle sounds fine (little high, but it's likely from messing with the IACV screw while chasing leaks).

Car details:
- 1995 ka24de
- Stock internals
- Enthalpy tune
- n62 maf
- GT2871r
- 850cc sard injectors (cleaned and flowed)
- Walbro 255
- Adjustable FPR
- Hallman mbc
- HKS ssqv recirculated
- EGR removed
- 91 octane
- Fresh TPS, coolant temp sensor, o2 sensor

It's been months...would love to get this baby on the road again... Tune? Something else? Any help is greatly appreciated!
Last edited by mt2forty on Sun Mar 24, 2013 5:52 pm, edited 1 time in total.

wannabethestig
Knows Some Stuff About 240's!
Posts: 303
Joined: Tue Dec 04, 2012 7:57 pm
Location: Silverdale Washington

Post by wannabethestig » Sun Mar 24, 2013 5:13 pm

Are those driving or idle afr's? You could try raising the fuel pressure 5# and see if you afr's drop a little bit. I don't know what wide band you have but some of them you can calibrate. My wideband will read "air" if the engine is off but ignition is on.
My wife "haven't you spent enough time and money on that car yet?" my answer "no"

The build thread-> viewtopic.php?t=58421&highlight=

mt2forty
Driving Mom's Station Wagon
Posts: 28
Joined: Sat Jun 02, 2012 3:12 pm

Post by mt2forty » Sun Mar 24, 2013 5:27 pm

wannabethestig wrote:Are those driving or idle afr's? You could try raising the fuel pressure 5# and see if you afr's drop a little bit. I don't know what wide band you have but some of them you can calibrate. My wideband will read "air" if the engine is off but ignition is on.
Those are idle afr's. Throttle drops the afr's into the 17.5 range.

I'm running an AEM uego wideband. With ignition on but engine off, the wideband reads a solid 14.7.

wannabethestig
Knows Some Stuff About 240's!
Posts: 303
Joined: Tue Dec 04, 2012 7:57 pm
Location: Silverdale Washington

Post by wannabethestig » Sun Mar 24, 2013 5:48 pm

When I rewired my plx m300 it read 14.7... the Bosch LSU 4.2 has a resistor specific to that o2 sensor. After I put in a new one with the correct resistor it would read air. The sensor has to heat up before it reads correctly. There should be no fuel reading at all with the engine off. You could have a leaky o-ring. If you pull your fuel rail and hold the injectors in it while directing them into a bucket and have someone else turn the ignition on (not cranking) there shouldn't be any fuel coming out.
My wife "haven't you spent enough time and money on that car yet?" my answer "no"

The build thread-> viewtopic.php?t=58421&highlight=

mt2forty
Driving Mom's Station Wagon
Posts: 28
Joined: Sat Jun 02, 2012 3:12 pm

Post by mt2forty » Sun Mar 24, 2013 7:03 pm

I misspoke regarding the 14.7 reading without the engine on. It reads 14.7 for about 10 seconds and then climbs off the charts (18.5). Thus, I'm thinking the gauge isn't reading incorrectly.

As for a fuel injector o-ring leak, I've pretty much ruled that out given that I pass a boost leak test with flying colors and I've sprayed tons of carb cleaner around the injector area with the car running and haven't found any leaks there. Key word as always - "pretty much" :-)

wannabethestig
Knows Some Stuff About 240's!
Posts: 303
Joined: Tue Dec 04, 2012 7:57 pm
Location: Silverdale Washington

Post by wannabethestig » Sun Mar 24, 2013 8:57 pm

I actually think your wideband is operating correctly. Is your base fuel pressure 43.5 without the vacuum line installed?
My wife "haven't you spent enough time and money on that car yet?" my answer "no"

The build thread-> viewtopic.php?t=58421&highlight=

mt2forty
Driving Mom's Station Wagon
Posts: 28
Joined: Sat Jun 02, 2012 3:12 pm

Post by mt2forty » Sun Mar 24, 2013 8:59 pm

wannabethestig wrote:I actually think your wideband is operating correctly. Is your base fuel pressure 43.5 without the vacuum line installed?
Yup - was actually just down there setting my fuel pressure again. It's at 43.5 without vacuum, but I did notice just now that when I connect vacuum again, it only drops to 38 or so...not sure what that means? Should be more in the 32 range. Thinking that could be due to my high idle (iacv screw in too far right now)?

wannabethestig
Knows Some Stuff About 240's!
Posts: 303
Joined: Tue Dec 04, 2012 7:57 pm
Location: Silverdale Washington

Post by wannabethestig » Sun Mar 24, 2013 9:02 pm

Yeah that's probably ok. Are you sure your tune is for the injectors your running?
My wife "haven't you spent enough time and money on that car yet?" my answer "no"

The build thread-> viewtopic.php?t=58421&highlight=

mt2forty
Driving Mom's Station Wagon
Posts: 28
Joined: Sat Jun 02, 2012 3:12 pm

Post by mt2forty » Sun Mar 24, 2013 10:22 pm

Definitely sure. I had Enthalpy double-check.

Enthalpy still thinks it's likely a wideband issue due to the fact that the engine seems to be running fine. Also just found out from them that due to the ROM they use, they block any consult program from seeing the o2 signal, which is why mine is reading 0v.

Freise
Knows Some Stuff About 240's!
Posts: 452
Joined: Mon Mar 30, 2009 10:29 pm
Location: St. Charles/Cape Girardeau

Post by Freise » Mon Mar 25, 2013 2:06 pm

What is your exhaust situation or chance of exhaust leaks around the O2 area? I've ran an open downpipe which caused the o2 sensor to read leaner than it was, and I've had the tiniest leaks in the exhaust elbow cause as much as 3-4afrs off...
95 240sx KA24DE-T
S15 Injectors
Z32 blow through

mt2forty
Driving Mom's Station Wagon
Posts: 28
Joined: Sat Jun 02, 2012 3:12 pm

Post by mt2forty » Mon Mar 25, 2013 2:09 pm

Freise wrote:What is your exhaust situation or chance of exhaust leaks around the O2 area? I've ran an open downpipe which caused the o2 sensor to read leaner than it was, and I've had the tiniest leaks in the exhaust elbow cause as much as 3-4afrs off...
Can't hear or see any exhaust leaks, though I haven't listened with a stethoscope or anything. Gaskets are all fresh, parts are all brand new, and everything seemingly lined up smoothly...is there a way other than stethoscope to find tiny exhaust leaks?

ViperGT
Knows Some Stuff About 240's!
Posts: 445
Joined: Fri Nov 11, 2011 1:26 am
Location: long beach

Post by ViperGT » Mon Mar 25, 2013 11:16 pm

i have any aem uego and i was getting lean readings and other funny full lean instances, only had it in for about 15k miles, turned out to be the wide band sensor, you said you replaced the o2 but are you talking about the stock one or the wideband one?
in a datsun 510:
arias 8.8 .020
eagle rods
clevite bearings
ferrea/exhaust supertech/intake stk
supertech springs and retainers
bc valve guides v2 cams currently crower 288/288 (no good)
port and polish
arp head, main, rod bolts
osk timing
current: custom log mani, TIAL mvr,
later: ati SD garret gtx3071 currently in my possession looking for gtx3576
custom downpipe
lol:
sdaigle240 wrote:beat that thing like it owes you money.

mt2forty
Driving Mom's Station Wagon
Posts: 28
Joined: Sat Jun 02, 2012 3:12 pm

Post by mt2forty » Mon Mar 25, 2013 11:26 pm

ViperGT wrote:i have any aem uego and i was getting lean readings and other funny full lean instances, only had it in for about 15k miles, turned out to be the wide band sensor, you said you replaced the o2 but are you talking about the stock one or the wideband one?
Talking about the stock o2, as I was concerned when consult wasn't seeing a voltage. I have not replaced the wideband one yet. Figured it was brand new, so it had a smaller chance of being bad.

However, given that the car sounds pretty solid and still reads 17.5ish while on the throttle consistently I'm starting to think wideband is the problem. Also, I ran the car with the sensor stuffed up the tailpipe (similar to how dynos read afrs) tonight and got a lean reading off the chart. Also tried it on my roommates Evo and got a lean reading off the charts despite his Inovate (which is reading at the downpipe) reading 15.

Freise
Knows Some Stuff About 240's!
Posts: 452
Joined: Mon Mar 30, 2009 10:29 pm
Location: St. Charles/Cape Girardeau

Post by Freise » Tue Mar 26, 2013 2:11 pm

mt2forty wrote:
Freise wrote:What is your exhaust situation or chance of exhaust leaks around the O2 area? I've ran an open downpipe which caused the o2 sensor to read leaner than it was, and I've had the tiniest leaks in the exhaust elbow cause as much as 3-4afrs off...
Can't hear or see any exhaust leaks, though I haven't listened with a stethoscope or anything. Gaskets are all fresh, parts are all brand new, and everything seemingly lined up smoothly...is there a way other than stethoscope to find tiny exhaust leaks?
I don't think this is the "proper" way but I take a sheet of notebook paper and hold one end of it, placing the other near the flange, any exhaust gas leaking will cause it to flutter (just make sure you don't set the paper on fire)
95 240sx KA24DE-T
S15 Injectors
Z32 blow through

mt2forty
Driving Mom's Station Wagon
Posts: 28
Joined: Sat Jun 02, 2012 3:12 pm

Post by mt2forty » Tue Mar 26, 2013 2:32 pm

Freise wrote:
mt2forty wrote:
Freise wrote:What is your exhaust situation or chance of exhaust leaks around the O2 area? I've ran an open downpipe which caused the o2 sensor to read leaner than it was, and I've had the tiniest leaks in the exhaust elbow cause as much as 3-4afrs off...
Can't hear or see any exhaust leaks, though I haven't listened with a stethoscope or anything. Gaskets are all fresh, parts are all brand new, and everything seemingly lined up smoothly...is there a way other than stethoscope to find tiny exhaust leaks?
I don't think this is the "proper" way but I take a sheet of notebook paper and hold one end of it, placing the other near the flange, any exhaust gas leaking will cause it to flutter (just make sure you don't set the paper on fire)
Or just be prepared to drop it quickly :-)

Thanks for the suggestion - I'll give it a shot tonight.

User avatar
airman
KA-T.org OWNER
Posts: 2137
Joined: Tue Jun 16, 2009 12:51 pm
Location: Anderson, SC

Post by airman » Wed Mar 27, 2013 7:05 am

In Nistune if I was in closed loop and my O2 sensor read 0v it would run lean. I'm pretty sure narrowband is 0v for full rich and 1v for full lean. So if it sees 0V it pulled fuel. Not sure if that's relevant to your issue but I figured I would leave this here.
R.I.P. 1990 Red Hatch - DOHC 5 speed // CP 9:1 - Eagle Rods - Clevite - ARP // Holset HX35 - 20psi daily - MSPNP2
8-bit wrote:You could spend your life building a ladder to the moon, or work for 5 years to pay for a trip.

Post Reply