bank 1 ltfts pegged at +25 but wideband shows very rich afr ???

[Gregs]

hey guys i have a weird issue going on here. My wife drive my truck today and she says it stalled on here while going into reverse. Dtc shows bank 1 too lean and random misfires. I hooked up the scanner and bank 1 is pegged at 25 but its showing a 10:1 with my wideband. Bank 1 sensor 1 is an lc1 simulated narrowband. i took it for a test drive and i don't feel like its any different than usual. help me out guys!

[Gregs]

i took my wideband out and put the factory nb back in. it seems like the trims go way out of whack mostly at idle. I sprayed carb spray around the intake gaskets and looked for exhaust leaks and can't find anything. I'm really stumped on this one, any ideas

[WeathermanShawn]

Gregs, what Temperature is your closed-loop set for (normally B4205)? Also, what is B3802 set to.

Your NB looks fine at cruise. Its pretty dead at Idle..

[Gregs]

Gregs, what Temperature is your closed-loop set for (normally B4205)? Also, what is B3802 set to.

Your NB looks fine at cruise. Its pretty dead at Idle..

yeah that was confusing me

B4205 is set at 131 as long as air temp>32F
B3802 is 160F

[WeathermanShawn]

It looks like your O2 and resulting LTFT starts functioning around 54C (129F) as it transitions from Cold Open Loop to Closed-Loop (by 55C).

There are over 21 Fuel Trim Cells (FTC) that can be logged (not all are active). One is called Cold Idle. That LTFT looks stuck on +18. I would reset my Trims.

Since the LS1's go into closed-loop so quick, I could not bring up a log to see if the NB is that 'dead' while in open-loop or not. I guess you could always try initiating Closed-loop at 34C and see if the NB wakes up early.

This is just my working theory at this point. Otherwise it is pretty confusing..

[joecar]

Swap the front NBO2s left/right and see if the large trim follows the sensor.

[Gregs]

ok i reset the trims and believe it or not the trims seem just fine now. I did a couple drives and i was having nearly perfect trims and the o2s were switching just fine. it it possible that the pcm was just kind of "stuck" on those values or something?

[WeathermanShawn]

Gregs, I was also going to suggest a NB switch, but interesting to hear your new Trim values.

I spent about 3 months logging FTC Cells and I always noticed when the car first starts up, it uses the existing 'Cold Idle' FTC..even though technically the car is not yet in closed-loop and Trimming. So yesterdays LTFT for that cell becomes todays problem. And to add to the misery sometimes that same FTC is added to WOT fueling (FTC 21). So clearing your Trims will reset all your FTC Cells, including that pesky 'Cold Idle' Cell.

Just make sure the O2 is working O.K. (you said it was)..We should know in a few days if your LTFT's will hold..

..Good to hear there does appear to be an improvement though..