Even when my wideband is reading lean the o2s are still in the 900s. I tend to beleive the wideband, b/c when the o2s start pulling fuel the car runs like crap. When I have them disabled in open loop the car runs good.

 

What do you mean by crap? Surging or bucking? a big cam always runs nice in open loop because it's rich, rich + overlap = builds cylinder pressure masking overlap.

 

It hesitates and misses badly.

When the wideband gets to around 16:1 I notice a loss in power. Arounded 16.5 to 17 I notice a little bit of a miss and hesitation. Much more than that and the car is hardly drivable. This is all low rpm and light throttle. I havent tried putting my foot into it with it so lean to see if it richens up.

 

If you disable closed loop, does what the wideband shows match the commanded open loop ratio?

 

I will have to look for sure, I know its not exact, but I think its pretty close. I beleive in the table my idle is around 13.8 and the wideband is between 14.5 and 15

 

This sounds like what I saw on my Impala SS. I tuned it to 14.2 in open loop which is pretty close to what the closed loop system aims for and it runs much better now in open loop.

Closed loop and big cams just don't work very well together. The cam timing causes excessive unburned fuel to get into the exhaust at low engine speeds which the computer tries to compensate for by leaning it out. Then it runs poorly.

It would be ideal if we had a way to specify that we only want open loop at low engine speeds, and let it go into closed loop at an RPM where closed loop will work properly. Some of the LS1 PCMs have custom OSes that allow this but not on the LT1. I tried using PE mode at low RPMs to fix this but the PCM appears to get confused.

 

I know what you saying about the valve overlap and the 02s getting a false reading, but there is a lot of guys running LE1 cams that dont have this problem.

I used to run a closed loop tune when I first got the car running with the heads cam. Seemed to run ok, just fouled o2s after a couple thousand miles. Thats whey I ended up going with the closed loop tune. I didnt have the wideband then so I dont know where the a/f was at.

Just for fun Ill recalibrate the wideband and see if my readings change at all.

 

It could have something to do with the O2 sensor placement, too... Hard to say. Issues like this are tricky to track down.

 

Don't know the solution to the current problem, but going to an open loop tune on an LE1 or LT4hotcam is just an ugly hack.

Boatloads of people run those and similar cams in closed loop with no problems.

 

Since you have some spare O2s, hook up a couple spares and leave them dangling in the engine compartment. If they read rich then, you know you have a computer/sensor problem.