super lean at idle

[tweak666]

i finally hooked up my wideband today. started the car, and for like 5 seconds the afr was 14.8, then it slowly started rising till it pegged the gauge. after a minute it slowly started bouncing between 15.1 and 17. i'm a little worried, as i've been driving the car, but not hard. it doesn't blow any smoke, temp stays steady, no overheating.
i was reading this thread: http://www.supramania.com/forums/showthread.php?p=159348&post159348

and a chart was posted that said that range was best lean for cruise, but this reading was at idle. wouldn't it continue to get more lean if i put load on the engine? i'm on the stock fuel setup.

 

[jdub]

Any codes?

 

[tweak666]

no, no codes

 

[jdub]

What other mods to the motor?

 

[IwantMKIII]

i'd check your stock 02 sensor.

your WB might have a simulated NB signal you can use instead of the stocker, try it out, see what happens

 

[turbojuiced]

First off, I noticed you lived in boca raton in florida. Ive been there before what a beautiful area that is, you are definitely lucky. Now onto the wb02

Under idle conditions it is normal to run lean. You should be reading anywhere from 14-18 and usually the gauge will go back and forth between those values. Now when driving but not under wot or boost it is normal to read a little leaner than usual like 13-14.5. But when wot and boost you should see those numbers drop vehemently from 10-high 12's depending on the type of tune and mods.
Now usually I would question whethor it has been installed properly but for the sake of purposes I ma going to assume you did install it correctly. If you have any doubts I would go back and make sure.

And you shouldnt run leaner if under load. If you have done everything correctly you should notice your afr's get richer.

If you have a data logger I would do a log run. This way we could really determine what is going on.

 

[jdub]

Ummm...on the stock ECU, it is NOT normal to run lean at idle. 13-14 during warm-up enrichment...14.5-15.5 at ops temp. If he has fuel mods, fuel piggyback, or a stand alone...well, that's different. Why do you think I asked about his mods? Why speculate?

 

[turbojuiced]

^Your absolutely right speculation is bad. However, you already asked about mods so I figured why ask again. No need to be redundant. However, just a question for you in your opinion what you think 14.5-15.5 afr's are? Lean or rich?

 

[jdub]

14.7 is a stoichiometric mixture...the stock ECU attempts to achive this AFR when not under load in an attempt for the most complete burn possible. At idle or cruise, this is perfect, neither lean nor rich...in practice you see the range I posted, mostly due to modifications. My car has 14.6-14.8 AFR's at warm idle....I see the same numbers at highway cruise. Under boost moving to WOT, different story...the ECU will drive AFR rich, usually in the 10-11 range.

 

[tweak666]

mods: headwork, ets intercooler kit, stock accordian intake w cone filter, stock turbo, hks dp, custom exhaust, stock computer, no egr, walboro 255lph.

i mounted the wideband in the factory wideband location and used the emulated signal to send to the cpu. i've been readin how the stock location isn't ideal for a wideband, but i figured it was ok temporarily just to make sure things aren't on the edge. could the location be the culprit?

First off, I noticed you lived in boca raton in florida. Ive been there before what a beautiful area that is, you are definitely lucky. Now onto the wb02

yeah, boca's ok, it is beautiful, but the people suck. i'm more of a small town guy, but i can't complain

 

[IwantMKIII]

mods: headwork, ets intercooler kit, stock accordian intake w cone filter, stock turbo, hks dp, custom exhaust, stock computer, no egr, walboro 255lph.

i mounted the wideband in the factory wideband location and used the emulated signal to send to the cpu. i've been readin how the stock location isn't ideal for a wideband, but i figured it was ok temporarily just to make sure things aren't on the edge. could the location be the culprit?



yeah, boca's ok, it is beautiful, but the people suck. i'm more of a small town guy, but i can't complain

wrong, WBo2 are very sensitive to temperature and condensation (you only have to worry about temp in stock location). You need to replace it with stock and add a new bung.

on a sidenote: there is no stock wb location.

 

[jdub]

No Lex AFM, 550's and AFPR? (I ask because you have a Walbro)
What kind of WB?
What are your AFRs at cruise and under boost?

The stock location is not ideal, but it should not affect readings. It's more a sensor longevity issue due to heat.

Just so you know, O2 AFR feedback (closed loop) in the stock ECU is a learned value...you could try pulling the EFI fuse for 30 sec to set to default. It is inoperative during open loop ops...engine start, after start enrichment, during power enrichment (hard accel to WOT), coolant below 80 deg C (iirc), and fuel cut.

What's confusing is idle is controlled by it's own ECU function targeting a set RPM based on engine speed, throttle position, vehicle speed, coolant temp and a few others. AFR should be fairly close to stoich at ops temp target RPM, slightly rich during warm-up.

It *could* be what you are seeing has to do with the NB emulation from your WbO2.
Or, (depending on the controller) the WB needs to be calibrated.

 

[tweak666]

on a sidenote: there is no stock wb location

to clarify, i meant i put the wideband in the stock o2 sensor location

No Lex AFM, 550's and AFPR? (I ask because you have a Walbro)
What kind of WB?
What are your AFRs at cruise and under boost?

no, no lex afm, stock injectors, stock regulator.
i'm running an AEM UEGO, the gauge type. i just hooked it up, and haven't driven it yet to see what the afrs would be under cruise and boost. that will have to wait till next day off. i'll try pulling the efi fuse and see what happens. i usually leave the battery disconnected though, wouldn't that achieve the same effect?
from what i read in the instructions, don't the aem's come precalibrated?

 

[tweak666]

new developement. pulled the efi fuse to reset the computer. when i started it up again, it only goes leaner than 16 at idle when i step on the brakes. what could be causing that? could it be a faulty gauge or ground?

 

[jdub]

Does it do it when you turn the head lights on? And how lean does it go...is 16 about max?

What are your AFRs at cruise (2500-300 rpm)?

After a bit of digging in the TCCS manual, I found that learned value is active at idle....give it a few days.

 

[tweak666]

the idle does change when the headlights lights are on, but it doesn't seem to change the afr as much as stepping on the brake. i think the max this time was 16.5. didn't get to take it out today, was blocked in the garage. idle today was 14.8-15.5 as long as i didn't touch the brake. could it possibly be a vacuum issue, isn't the brake booster vacuum driven? i'm not sure how that would effect the afr though.

 

[jdub]

That's a thought...the brake booster is vac driven. Might be pirate air.

That AFR range at idle is pretty normal otherwise.

 

[Mr.PFloyd]

Was it a new wideband? from what i read you have to sort of power it up the 1st time without like power to it.

 

[TargaMK3Turbo]

Hmm, I run in the high 15s at idle and 11.6-11.8 WOT, seems fine to me... I have almost the same type of mods.

I'll have to keep up on this thread, maybe I should do a little more tuning...

 

[jdub]

A bit high at idle is no big deal...you're starting to push it at WOT IMO. Not much, but I would want to be at 11.5. I tend to go to slightly rich of an optimum 12.0 target at WOT...just in case. Detonation at WOT will ruin your whole day.