Superado

iTrader: (37)

left the truck at a shop last night and damnit...the cats were missing and replaced by straight pipes when I picked it up...

however, on the way home my a/f was going crazy...especially when I would let off of it...it would flash up to 17 - 18 then back down...

same thing this morning on the way to work

any thoughts?

Nick™

iTrader: (2)

did you disable the rear o2 sensors?

edit:
and where's that shop at? I want to park my truck out there and just let them try to get my cats j/k

Superado

iTrader: (37)

Cablebandit turned them off w/ HPTuners awhile back...but I believe he just checked "do not report"...does that make a difference?
then I installed the DynoJet WBC...haven't seen it do that before...been monitoring it for about a month or so now...
it was dropping to 11.5 @ WOT last night and this morning as well...current tune was only dropping to 12 @ WOT pre-cat removal...
the spikes were happening after letting off from part throttle as well as WOT...

02sierraz71_5.3

iTrader: (2)

cat overtemp needs to be disabled

Superado

iTrader: (37)

could you elaborate a little...what does that do or not do exactly?
thanks...
btw...just spoke w/ cablebandit...he said that the system is supposed to cut off fuel injectors when you take your foot off...some sort of fuel economy feature or something...now...why it didn't do that before I don't know...something to do w/ the cats evidently...

dewmanshu

iTrader: (4)

He should of chose "3-No error reported", same thing I'd imagine. If your fuel trims are opertaing, remember they are always learning, not that deleting your cats and turning off rear o2's should effect your afr. To my knowledge the rear o2's aren't gonna effect fueling. They just monitor the cats. A few things with the COT, and other tables may effect your afr, but i highly doubt it if the codes are turned off as you say.

So, with that said, could be lots of things, but a lean spike at throttle release isn't bad IMO. As long as you have safe afr during load or any amount of decent cylinder pressure you'll be fine. Hell, with a lean 0%TPS, you should get better mpg.

Maybe your dcfo is kicking in.

dewmanshu

iTrader: (4)

wouldn't this only come on errr go into effect if the pcm saw an overtemp in the rear o2's? If they are told to not report, this "theoretically" shouldn't matter right. I agree they SHOULD be turned off, but curious hwo it effects the afr just by removing the cats, codes have been off all along. (not that i doubt ya, just curiuos)

Superado

iTrader: (37)

"3-No error reported" is what he did I believe...
side note...DJ WBC a/f sensor is installed in driver side post cat location...stock rear sensor is still installed on passenger side...

This is exactly what Jerry said...I had never heard of it...wasn't doing it before...

thanks guys...

trever1t

iTrader: (14)

Not to hijack but I am experiencing a similar issue but I have Magnaflow HiFlow cats. It reads 14.7~ most of the time then goes way lean (17) or sometimes even reads rich (13) randomly at light partial throttle??

Superado

iTrader: (37)

same here...