The coarse BLMs at idle are somewhere between 150 and 160. The fine stay within 10 of 128, usually around 135 or so. At part throttle the coarse drop down to about 120. This would make sense with my combination. But my plugs are blacker than the prince of darkness. The header bolts are tight, there is no known vacuum leak, and no matter what I try the idle still stays lean according to the computer. I even lowered the injector constant to 22lbs from 24 and pushed the fuel pressure up to 50 psi.


Any suggestions?

 

Just as an update the fine BLMs climbed up to 182! This was while the coarse was at 160. The O2 sensor would hover around 100 to 200 mV for a while then jump up to about 700 or so while the BLMs are climbing that high and stay there. The idle would smooth out a bit then everything would take a few steps backwards and go through the cycle again.

A friend of mine brought up the question of a false lean condition. Thinking the cam has alot of overlap the exhaust may contain false amounts of oxygen causing the O2 to sense lean.

Here are the specs:
262/270 @ 0.006
218/224 @ 0.050
494/500 lift
114 LSA

Any comments?

 

Your cam specs shouldn't be a problem...I have more duration than that....Checked the O2 sensor? If it's a new engine the gasket sealers can plug it up in a few hundred miles....Is the O2 sensor in a header collector? Heated? I keep leaning towards a false lean due to air leak before the o2 sensor....or the sensor itself.

 

I have the SLP headers with the Earl's header gaskets, the ones with the replacable soft graphite inserts. The bolts are as tight as I can get them and I don't hear any exhaust leaks. The O2 sensor is the one wire style and about a year old. Funny you should mention it, the motor has just been rebuilt after all my unbrella seals were shattered. The motor only has about 350 miles on it but the O2 sensor was showing VERY lean even at cam break in, the plugs didn't show an overly rich or lean condition then.

Is it possible for the O2 sensor to get stuck at a low reading while not in power or acceleration enrichment? I ask because it will show 600 to 900 mV when I give it some gas. I do have an old O2 sensor lying around so I'll give that one a try, but it may be original to the car. Can these things be cleaned with carb cleaner or something?