NHTKID

so heres the deal, for one i know that afr at idle is fine, but there is more to it. not to mention im anal and want the thing running perfect. my car is a stock j4 sr20det with a j4 wiring specialties harness. Its running fine, my plugs are a tad white but nothing TOO terrible, however at WOT my afr is between 11.5-12.. with an occasional 10ish.. This is what has been bothering me though at idle its a consistent 16.4 and from -20 to -15 itll be around 15.7, then from -15 to 5pds of boost part throttle (light load) it actually gets leaner, averages 16.5 to 17.5 with the occasional 18 which is bad. Its funny though, ive gone through 2 coolant temp sensors because when i first start the car even when the motor is warm, itll start and hit 1500 rpms, and slowly idle down like its a cold start lol, during which time the afr's are beautiful, 13.5-14.7 part throttle and wot 10-11.5... so naturally i thought it was that, its been replaced twice with the 96-98 ka24de coolant temp sender (round type, as i have a 97 s13 type x sr)..

im semi dumb founded. any help would be greatly appreciated.




i have also considered the fact that im not COMPLETELY stock and since the ecu is a stock map it might be running lean and i need a tune, is that a possibility?

sr20det blacktop j4
intake
full 3 in exhaust straight pipe
blitz FMIC
walboro fuel pump
z32 fuel filter
hks ssqv bov
vacuum directly to wastegate for 7pds since im having this issue
aem wideband
boost/vacuum gauge
oil pressure gauge

ultimateirving

Those are good AFRs for cruising and good for WOT for 91. Whats the problem are u getting knock? dont Drive Part throttle into boost if you dont have to.

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NHTKID

well see when im driving around not getting into boost, between -20 and 0 vac/boost its between 16 and 17.. even when going up a hill under load and i give it gas not hitting boost, its still in that area of 16/17.. with an occasional 18 hit.. ive heard that its lean, and ive also heard that its normal.. is that a normal thing? i just want it to last ya know

ive read the average of 14.7-15.3 idle
and part throttle 14-high 14's and
wot 11.5 or under is pretty normal

NHTKID

oh and im using 93 oct

NHTKID

this title should be 16.5 afr idle/part throttle normal? lol whoops

NHTKID

so i assume 16.5-17.5 part throttle/idle/light load is not abnormal? or should i go ahead and get an safc just to make sure everything is good and that im comfortable with the readings?

4x4le

Safc is a joke and yes you do have a problem so patching it with a safc (tune) is just going to mask the problem.

I would look at the maf and tps really close. They are most likely the cause.

4x4le

Oh, id also look at the o2 sensor. That should not allow it to run lean at idle and part throttle but would not help you where your lean at 0-5lbs.

Ill say this too, get a 2nd opinion on the wideband, like run an innovate lm1 in the tailpipe to see if you have different readings. I dont trust aem widebands. I have had many customers with them and my innovate widebands read right with the widebands on dynos while the aem widebands will give different readings.

NHTKID

ok ill clarify everything ive checked so far, everything is working properly.. from tps, to maf, to cas, to blah blah blah.. that being said, the car still starts and idles high initially even on a warm start, could the cts be the culprit?
i have installed a 96-98 cts from a ka24de..

Also, ive checked fuel pressure. it was around 34 with vac line connected, right at 43 with vac line disconnected. this leads me to beleive perhaps my wideband needs recalibration?
although ive never heard of aem widebands needing to be recalibrated. its located on my DP right after the turbo elbow. It was just resealed with new metal gaskets from the manifold to the DP for this reason.

could it be an issue with the fuel pressure regulator or would the symptoms be worse then i described? cause the car runs strong! almost as if it were the wideband reading incorrectly.. im not getting hard or bad idle by any means even when its reading that high.

how would i go about checking the CEL on a j4 ecu? i dont have a normal screw as i did on my old blacktop.. is there a way to wire the ecu to the dash to get it to flash? or do i need a nissan consult?

my 02 voltages were checking out fine, could this lean issue be a common symptom of a bad 02?

im running bkr6's gapped to .028

maybe ill take a video of me driving around for you guys

4x4le

I dont get what your saying about you hooked it to a computer and everything is working allright, but your still wondering about sensors being bad..... If your just looking for codes your doing it wrong. The laptop isnt going to do further diagnosis other than what the ecu can do. The laptop provides you with gauges for every sensor if your using a program like datascan and you can watch all of the gauges and see if anything funny happens. If its 60* outside and you havent started your car yet that day and your cts says something far away from 60 look there. Other gauges have tricks to watch for and the ecu cannot always tell when they are screwed up.

NHTKID

im uploading a video for you, i only wondering about sensors, cause my check engine light is on, but it said no codes, ok to drive.. so im just curious..

today when i would pull my maf closer to the bumper (its still on the rubber intake tube) the afr would go to about 15.3 and when i let go it would go back to 16.5.. i rigged it close to the bumper to keep afr's down after i noticed that, and when i shut my hood afrs went lean again.. should i mount a smooth spacer pipe to make sure air flow is perfect when blowing by the sensor?

4x4le

Your not running an air filter, are you?

NHTKID

lol yes i am, not running one would not be smart.. im thinking the air doesnt have enough time to smoothen out and read properly.. but not sure.

Here i uploaded a video last night for you.
SR20 240 running lean - YouTube

NHTKID

and incase anyone didnt want to read the whole thread, here is a vid of the car driving

NHTKID

oh and that random scrape sound, was a trucks starter as i drove by lol

NHTKID

also, it only does it when warm.. any suggestions?

EDacIouSX

wait.. stock ecu and you have these mods listed?

intake
full 3 in exhaust straight pipe
blitz FMIC

You know these parts changes the air flow into and out of the motor right? So that would explain why the Stock ecu AFR is off? I didnt read the entire thread but I didn't see any mention of an aftermarket ecu/ems

steve shadows

The afc is going to throw everything off on our cars. It's a hot wire maf so it's very dependent on having the correct voltage and resistance down the line to the ECU to feed back the right fuel input to the motor.

I would also check for vacuum leaks. This will cause a lean condition in lower throttle conditions but not so much under load as the FPR loads up and sprays more pressure behind the injectors under load.

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NHTKID

so obviously the afc is questionable considering there are mixed reviews right now lol, also if that were true under load then why at part throttle boost is it still in the 16's and 17's?

what would i need to do to pull codes off this j4 ecu, if it doesnt have a cel light screw?

i have a fuel lab fpr that im going to be putting on next week hopefully, that might help, but i do have an safc coming in as well.. ive been thinking that maybe the resistence becomes a bit much under heat and the injectors arent firing at the correct duty cycle? idk im probably thinking way to far into it.

NHTKID

ya ive been told that it may only be that i need a tune, i never plan on going for more then basic bolt ons so i would assume an afc would be fine as i know plenty of people running them... then again ^up there someone was just saying how it would be bad for me to do

mantas

Blah blah blah, exhaust leak. I had the same issue about 4-5 times. Fixed the leak and back to normal. Even the slightest leak will trip up your gauge.

NHTKID

I replaced from the manifold all the way to the dp with brand new metal gaskets.. Wasn't cheap either. No exhaust leak

negrosx13

Dude aem widebands aren't that good. Since 1day of my swap, dam wideband has been reading wrong. Check the resistance on the injectors, I've pretty much have changed about 3 so far


Btw you need a inspection

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NHTKID

haha you noticed that huh? yeah i need an inspection.. what should the resistence of the injectors be? dude youre located in houston? im in huntsville/conroe area

4x4le

People that use safc's are just as dumb as the people that drive around untuned....... So there you go.......

You have 2-3 people in this thread saying no on the safc, and 2 people saying you shouldnt trust the aem wideband and what you get from the people trying to help you is "i should buy a fuel pressure regulator that is adjustible and an safc"?

Well, hopefully you pay closer attention in your next thread when you ask about rebuilding the engine.

NHTKID

Ok you arrogant know it all, apologies for not being the end all of knowledge and mechanical experience.. I'm just trying to get the car running right. And I've checked the o2, resistance of each injector was 11.5 ohms, there are no vac leaks, my bov is vented,so i plan on recirculating, there are 0 exhaust leaks, Maf and tps are fine... So unless you can pinpoint the issue after having watched the video and read the thread then I'd love to hear your input, that being said the only other logical thing being that other things have checked out would be to get a tune.. Not just with an safc, but a rom tune which I'll be doing as well, but I don't need you to be being rude about it when I'm having an issue with the engine.. The help you have provided previously has been much appreciated and your continuous help throughout this diagnostic will also be appreciated.. With my fuel filter being a bit old I'm gunna try a new z32 filter this week and see if that helps, if it doesn't even help a little bit I don't know what else to check.. Today I disconnected the o2 at idle and it went straight rich, plugged it back in and went right back to the 16's, disconnected Maf and it ran terrible.. Any other ideas?

Kingtal0n

Here are some possibilities for you to consider:

1. the wideband is wrong. MAYBE. Consider for a minute- if it IS wrong, then your engine may have NO PROBLEMS currently and where located.

2. The wideband is right, and something else is wrong. WHAT ELSE?
there are many possible causes for this situation, such as exhaust leak / improper sensor [location/environment]

So I feel the proper course here is to verify the wideband FIRST. Dont do ANYTHING dont touch ANYTHING do not exchange ANYTHING before you make sure the wideband is reading right.

here is how I would start (from the cheapest quickest solution as always do the cheapest, easy most simple things first)

Buy a narrowband sensor. Ensure there are no exhaust leaks. Put your hand everywhere when the engine is cold feeling for puffs of air-
Run the narrowband sensor and see what the wideband says. If the narrowband is working, and the ECU is completely OEM, you should be seeing it swing around 14.7:1 air fuel ratio, during the times while yours is reading 16.5 right NOW.

Here are the possibilities, and the solutions for each now (the next step)
a. You install a new narrowband and the wideband reads 14.7 at idle/cruise. Everything is fixed.
b. You install a new narrowband and the wideband STILL reads in the 16's. Proceed with:

Install ANOTHER wideband sensor. This is weighed against the probability you have access to one. The AEM requires or advertises that "no calibration is necessary" for their units. You need to verify that the AEM is reading BAD, because the only other explanation for what you are seeing is an issue with actual fueling. Which means your engines life is in mortal danger. Please understand that if that wideband is RIGHT and doing its job you may need to fix an actual fuel problem which can extend from the tips of the fuel injectors to the ECU itself, all of which is MORE costly and time consuming that just swapping a wideband to verify the issue is actually fuel related.

4x4le

arrogant, confident, call it what ever you want but know it all is not it. If I dont have a good hunch about something I keep my mouth shut. You still havent dont the suggestions. Your ohming stuff out and I may have not been clear enough but you would be surprised how many times that does not work. We have a known bad ignitor with the cover off that you can see is bad that "checks" just fine per the fsm....
Tps many times will check just fine by the fsm because the fsm is not critical enough and does not take into consideration that the ecu can be reset under the base idle adjustment (tune or no tune) allowing it to look for a different voltage closed. Checking at closed throttle and full throttle is not enough. Linear voltage increase is necessary with the tps, and "dead spots" can lead to your very problem.
Your wideband does look very "suspect". I cannot believe aem continues to put out such a terrible product as critical as a wideband and are arrogant enough to somehow think they need to calibration, when they use the same sensor as 90% of the other wideband manufacturers that do require calibration.

If your wideband does read wrong, a tune is probably all you need. And there is no reason for a safc if you have a good rom tune.

recirculating your bov has nothing do do with this, it is most likely to cause rich problems if your not, not lean.

Anyways, You dont have to listen to me, that is your choice. And it is my choice to not help when I dont think people are willing to listen.

Good luck

woa, Its note-worthy that we agree on something

NHTKID

ok, ill change that this week and let you know the results. i appreciate the help. Also its only lean when warmed up, during the warm up process its in the ideal afr's

NHTKID

4x4le: dude you obviously know your shit and that help is much appreciated, all I was saying is you didnt need to come off in that rude way when I'm obviously struggling here. The safc has been on its way, the fpr is sittin in the garage uninstalled because I don't have the fittings.. It wasn't that I wasted money on those particular objects, so like I said above I'll change out my narrowband and let y'all know the results, if it doesn't change anything I'll see if perhaps the wideband is reading wrong