Hoping to get some help on what I hope is my final problem with this. First a little background: 1985 vette, repinned for a '165, running a modified ARAP code for my '85. No EGR, car is basically stock, with a slightly opened intake, roller rockers, and headers w/3" mandrel bent exhaust.
This is a frame-off renovation, so it has been a while since it has been on the road regularly....I have spent a lot of time on the modified code, and have it just about where I want it, with the exception of the idle. I've finally (I hope!) corrected a surging idle problem, and I have the BLM's in the 125-130 range for all cells, except cell 0, my idle cell. In open loop, the BLM's are of course, 128, but the Target AFR is in the mid 15's...in closed loop, I am extremely lean, at 160 BLM....now I've been working with the first four entries on MAF Table 1, but it seems that no matter what I do, I'm always extremely lean....GPS is in the 7-10 range, idle is at 700, so everything appears to be as it should, but I can't get it to go any richer...am I missing something here?? Done an awful lot of reading on this, and it seems that I'm working with the right thing to adjust this, but I'm just not making any headway...everything else seems to be right on the money, and the car runs better than I remember, just got this very lean idle....

Thanx for any insights you might have...

Cheers,
Michael

 

My first guess is a cold O2 sensor, as sometimes I've seen them get cold but not be in the 350-550 mV dead range, just barely.

Try a heated one, even if this isn't your problem.

What do you mean the "Target AFR is in the mid 15's"?? Should be 14.7 at all times in closed loop. If you mean the wideband is showing mid 15's, then it means your O2 sensor is probably ok, and something is either adding air behind the MAF, or before the O2 sensor. A vacuum leak at idle would be the usual suspect.

 

RednGold, thanx for the reply....O2 sensor is brand new heated Denso...according to Datamaster, working correctly, lovely swing once it goes to closed loop....the target AFR in the 15's is what it shows at idle in cell 0 in OPEN LOOP....with the BLM's at 128....seems awful lean to me...once it goes to CLOSED LOOP, the target AFR does go to 14.7, and the blm's shoot up to 160...I've tried working with the idle cells in MAF Table 1, but I'm not making much headway....ALL other cells are in the 126-130 range...just looking for some help to richen up the idle cell....

Cheers,
Michael