Intermitent commanded A/F to 16:1

[mysunnshine]

I have something weird going on in my tune that I have not seen before. Intermittently my commanded A/F will go from 14.64 to 16:1. I have gone thru my cal and I can not locate anything that would be commanding it to do so. My open loop commanded the entire time stay at EQ 1. What else is there that I am obviously missing that could change that commanded value? I am at an absolute loss on this one....:mad::ranting::bash:

[mysunnshine]

Anybody? This is happening during closed loop by the way.

[ScarabEpic22]

Log and see if the PCM thinks it's in idle mode when this happens, you have the tune setup so the PCM may command 15.45:1 for certain idle conditions. Does it do it under load or just while coasting?

[mysunnshine]

I have only logged it cruising above 2000rpm.

[mysunnshine]

Where are you seeing that 15.45?

[ScarabEpic22]

B3607, Fuel->Mixture->Parameters

The log shows 1150rpms and 54-55kPa when the commanded AFR goes to 16.

[ProperTuningOG]

150 degree cruising IAT and a bunch of voltage drops below 12v..... whats going on there?

[mysunnshine]

The engine is in a Jeep CJ which doesn't leave a lot of room for a cold air intake. It's taking in the air from behind the front fender but it also tends to get fouled by exhaust heat because my intake "box" isn't complete yet. It's also 100 degrees here in Phoenix already too. :( The voltage drops are from my Lincoln Mark VIII fan cycling on and off.

[joecar]

150 degree cruising IAT and a bunch of voltage drops below 12v..... whats going on there?
Alternator failure.
Wiring failure (breakage).
PCM failure.

[mysunnshine]

Alternator failure.
Wiring failure (breakage).
PCM failure.

I actually flashed another PCM with the same OS from a different calibration that I had and hand transferred the cal to the new file without any copying to make sure that I did not get a corrupt OS but with no change so a bad PCM is out....

[joecar]

mysunnshine, what year/model/vehicle is this...?

[mysunnshine]

It's a 6.0L/4L80E in a 82 Jeep CJ. As an update to this, I took it out for my second out of town trip with it last week and ended up losing the PCM fan ground control while out on the trail. When I got back to the house, I swapped in the extra PCM that I brought along and all of my problems went away. I also noticed a few other slight changes with the PCM swap such as coolant temp. The coolant temp data and the dash data were always 10 degrees different from eachother. With the PCM swap, it's now within 1 degree. With that, I will also assume that the IAT would have a similar offset now. With the PCM swap, I did no other changes. Before my trip, I did recheck the resistance for the PCM grounds to the battery just to make sure I was not inducing the issue myself. So I actually had a unicorn fail because PCM's so rarely fail......

[joecar]

Can you drive with a voltmeter connected to battery to see what voltage does...?