Running lean w/o boost HELP

[archenemy236]

Hey Guys I need some more help I installed a AEM UEGO Wide band into my Test pipe last night it started to run a 15.6 idle speed and a 17.8 under cruising conditions isnt this much much to lean for this engine? and under WOT it was a 13....I need help since this is my only car I have access to.

Mods are as follows:

3" exhaust w/downpipes
Power Intakes
its running stock boost off of the waste gate (I do have a boost controller but im not touching it)
Tune is stock I believe...

[nelsonmxmarc]

O2 sensor perhaps. Or maybe your maf/mafs are a bit weak.
There's a tutorial on here about resoldering mafs by pulling the black cap off the top. Quite simple! I would also change your O2 sensors and have a good listen to your fuel pump, make sure she's running well by ear before having to hook up a fuel pressure guage.

What RPM are you idling at? How does it run normally? You said you hit WOT, does it stumble or fall on its face?

EDIT: your test pipe, it's a TRUE cat delete and not some sort of hi-flo cat? Because if it's not through and through, you'll be reading the incorrect AFR's.

[Skym]

That's really lean throughout powerband. 14.7:1 is ideal at idle for stock engine and should head towards 11.6:1 (safe A/F ratio) or richer at full boost under WOT until rev needle hits rev limiter. I would think clogged fuelfilter, failing fuelpump, failing fuelpump voltage regulator, FPR problem on fuelrail.

Or like mentioned in post above, wideband o2 sensor is too far from engine (anywhere between turbo, cat is recommended). o2 sensor should have instructions on where manufacturer mentions the distance from turbo, where boss fitting for wideband o2 sensor to be placed.

Also I would stop driving car and catch bus until you fix this, as if those A/F ratio's are accurate, could blowup the engine.

I would do a compression test after fixing this problem to check rings, etc. Just for piece of mind.

[anthony]

i thought the o2 sensor was supposed to be closer 36 inches from the exhaust port
maybe its showing lean because of maf/mafs as nelson said or it may be fine and its sensor placement

[archenemy236]

Its a true test pipe with o2 bung with my wideband in that spot.

[archenemy236]

Idle is at 1000RPM and its very very smooth, under WOT it hold and it drives very well no stutters other than at 2500rpm without boost.

[Skym]

On GTR with twin frontpipe (3 cylinders per pipe), o2 sensor probably needs to sit further back, near cat to read all 6 cylinders.

[archenemy236]

Well in the test pipe (Cat) should be fine from what Ztune told me..

[M13]

Mine is beyond 18 at idle, 13 on load then 11 on half throttle to a 10 from 3/4 to full throttle.

[archenemy236]

So then is running a 18 while cruising very light gas ok to spike to?

[nelsonmxmarc]

18 afr at idle? That's very lean.. sounds like a possible air leak? I had that when one of my grommets failed on the head that supported my number 4 injector. Ran fine otherwise, but the air draw at idle pushed my ecu to believe it was a TPS fault.

I dont think that's normal dude.. floating around 14.3 to 15.5, stabilizing every once and a while at 14.7, is a normal idle table AFR.. The only reason your AFR's stabilize when driving is because it changes to running tables on the ECU and richens the titties out of it to get as close to running stoich (14.7) at ~100km/h, as possible. If you check your codes, it's likely you're throwing a 43 like i had.


Spiking to 18 is fine. You have to realize that these gauges are very sensitive and they're not nearly as accurate or poignant as you may believe. They're a reference for monitoring safe AFR's, not to the tee though, mind you. So off throttle, or very light on the pedal is probably going to jump around rich to lean only because small altitude changes in the road will yield you to either increase or decrease speed.. AFR's should only really be watched when hitting WOT to limiter, and at idle.. A safe AFR to redline like Skym pointed out is definitely around 11.3 to be SAFE. It should taper a bit towards the stoich side as it climbs but nothing over 12 from what i've seen on stock maps... Can lean out to gain power, but then again, prone to knock.

[archenemy236]

While im light on the gas its popping and has a stutter when i try to accelerate and it runs a AFR of about 16-18 :\

[M13]

18 afr at idle? That's very lean.. sounds like a possible air leak? I had that when one of my grommets failed on the head that supported my number 4 injector. Ran fine otherwise, but the air draw at idle pushed my ecu to believe it was a TPS fault.

I dont think that's normal dude.. floating around 14.3 to 15.5, stabilizing every once and a while at 14.7, is a normal idle table AFR.. The only reason your AFR's stabilize when driving is because it changes to running tables on the ECU and richens the titties out of it to get as close to running stoich (14.7) at ~100km/h, as possible. If you check your codes, it's likely you're throwing a 43 like i had.


Spiking to 18 is fine. You have to realize that these gauges are very sensitive and they're not nearly as accurate or poignant as you may believe. They're a reference for monitoring safe AFR's, not to the tee though, mind you. So off throttle, or very light on the pedal is probably going to jump around rich to lean only because small altitude changes in the road will yield you to either increase or decrease speed.. AFR's should only really be watched when hitting WOT to limiter, and at idle.. A safe AFR to redline like Skym pointed out is definitely around 11.3 to be SAFE. It should taper a bit towards the stoich side as it climbs but nothing over 12 from what i've seen on stock maps... Can lean out to gain power, but then again, prone to knock.

You mean the rubber grommet (seal/o ring) for the injectors on the manifold right?

Yeah all mine were leaking when testing for a boost leak. I believe the extra air draw (in essence vacuum leak) is what makes the AFR high.

Anything more than 25% throttle is causing my car to be lower than 13 however.

10 at 8psi lol... I guess the o rings leaking air is also leaking boost, therefore the fuel dumped by the ecu for the MAF reading (before leaking at manifold) is rich..


on this note, make sure your deatschwerks injectors come with OEM o rings, not deatschwerk ones.

[Skym]

Check fuelpressure first to eliminate it as a cause of stuttering, hesitation. If ok, then check for airleaks behind MAF's (can make engine stutter if intake hose clamps are loose). Then check TPS, as it's another cause of hesitation.

[nelsonmxmarc]

make sure your deatschwerks injectors come with OEM o rings, not deatschwerk ones

Lol. Good call! OEM or cavalier o-rings are the BEST fit.. I resorted back to my oem RB20 injector o-rings, 15 year old o-rings over new ones. No leak.

And yea, the grommets i'm talking about are exactly those, the ones in head. It's easy to mess those up when putting them in, and after a bit of heat, they tend to melt and deform.. really big pain in the ass.. I went through 5.. 2 of which went straight into my engine lol.

Guaranteed you'll be happy to swap those out! Find a front clip or a junker and just pop them out for free!