Is it really lean or not?

[ShinodaVette]

A quick question; hopefully.

My NGK AFX wideband is pegged at 16.00:1 (it's max reading) at idle. I think it isn't much higher than 16 because I do see very slight drops into the 15's but it mostly stays pegged at 16. Driving around town in an easy - normal manner results in the WB showing some high 14's but mostly low to mid 15's for AFR. If I get in the gas a bit, but not into PE, the AFR gets a little richer. I also see it a little richer after coming off of a little throttle. All the numbers seem quite lean to me.

So, after reading everything I can manage to find, I'm wondering if I can trust the WB right now. The cam is a Comp 222/224 .566/.568 lift w/112 LSA. Am I really running that lean? Is the cam affecting the WB readings due to overlap? Is there some other problem? I also have Kooks LT headers w/no cats. Everything else is stock.

I am also seeing misfires that I am just starting to track down but am wondering if they are due to a lean condition.

[jimmyblue]

Well, I think that's the dirty secret of wideband
meters - any air at all in the exhaust can fake it
out.

But there is also the question of, does the car
really -want- true stoich, as well as "is indicated
14.7 really 14.7:1?".

EPA says you must (local null for pollutants when
cats are working right).

You ought to compare the wideband reading to
what the narrowbands are doing in the higher
RPM, closed loop areas. They should agree
reasonably, though simple things like O2 switchpoint
voltages can bend that a fair bit.

If your wideband has a self-cal feature you may
want to run it.

If you can program the output profile, then set
it up so 10:1 - 20:1 always puts out the value
you want for 12:1 (record this), 15:1 (ditto),
18:1 (ditto) and satisfy yourself that the scan
tool reading matches. Many, or most widebands
don't do well at all.

Knowing your instruments are right, is key.