RandyZ71

I have the PLX wideband installed in my '06 with the L-33 engine. I haven't logged the wideband yet with HPT, but the gauge fluctuates quite a bit. It isn't a smooth fluctuation either. It seems to jump from rich to lean to rich etc... I figure this is the closed loop system over adjusting back and forth, but it just doesn't look right. It could also be that it is a digital guage and I prefer (and am more used to) a needle. When I go WOT, it jumps to around 12.8 and starts to progressively and smoothly get richer as it nears the shift point (~5800). I want to lean out the open loop tune a little, but the gauge behavior is more like what I was expecting.

The PLX is wired directly to the battery for the + and to a good chassis ground for the -. I first thought I needed to wire it differently, but then I started doing WOT runs and the gauge responded like I expected.

Truck is stock except for a Magnaflow cat-back and the "in progress" tune. I had a 4" aluminum tube and silicon boots between the stock airbox and tb, but went back to the stock air tube becuase I thought it might be a resonance issue with the MAF. Going back to the stocker didn't make any difference. I don't want to start really dialing things in until I feel good that the wideband is behaving correctly. I tuned it this far with the fuel trims which are all within +-4 of 0.

Is this normal behavior? Thoughts and suggestions appreciated...

charcold-bowtie

iTrader: (10)

I have the plx as well. Mine seems to move aroundd quite a bit during crusing operations but at WOT mine will hold steady and maybe move a tenth at most during the duration of a gear.

truckmann

iTrader: (8)

Sounds like normal closed loop operation to me. Mine does the same.

cmitchell17

"Truck is stock except for a Magnaflow cat-back and the "in progress" tune. I had a 4" aluminum tube and silicon boots between the stock airbox and tb, but went back to the stock air tube becuase I thought it might be a resonance issue with the MAF. Going back to the stocker didn't make any difference. I don't want to start really dialing things in until I feel good that the wideband is behaving correctly. I tuned it this far with the fuel trims which are all within +-4 of 0."

I did the same thing, except I traded mine for a stock LQ4(I think LQ4 might be LM7) 2500hd airbox. Rats chewed through my stock airbox and if the airbox supports a 300hp Lq4 I figured it would support my 5.3. I figure if gm spent money desigining that thing it had to do something. It didnt make any diffrence for me either.

RandyZ71

Going back to the stock air tube seems to have helped the fluctuating Wideband readings . It still goes from rich to lean to rich, but within a narrower band and the gauge is just generally not showing as wide of a variation as before. I read somewhere that the MAF signal is in mHz? so I'm thinking maybe my home-made intake was playing havoc with the sound waves? Or more likely, even though I used quality stuff including T-clamps, there was a small leak somewhere.

I can't tell any difference performance wise, but the gauge behavior is more like what I was expecting to see, more linear and less "jumpy". Now I need to get busy and to fine tune everything!

Thanks for your replies!

TurboJohn6

iTrader: (12)

Mine does the same thing too. I thought there was something wrong with it at first. I then remembered my days of tuning my Turbo Buick with my OTC. The rich/lean light used to switch real quick in closed loop. Once you go to open loop it settles down quite a bit.

TurboGibbs

iTrader: (6)

When in closed loop (cruising and idle) it should switch back and forth from rich to lean. Watch your HPT scanner, Your narrow bands are doing the same thing. A narrow band O2 only knows 14.7:1. It is either richer than that or leaner. When richer it tells the computer to pull fuel and leaner it tells it to add. Your fueling is actually going rich to lean very rapidly. When you enter into PE mode (WOT basically depending on when you have the PE to come in at) It should stablize.

cmitchell17

Anybody who tunes that sets their switchpoints to low milivolts at low loads. Does your switch points get closer together as loads increase?

TurboGibbs

iTrader: (6)

Mine doesn't switch. I run in speed density all the time.

RandyZ71

The switching was the same at all load points except WOT, very erratic and fairly large swings (16.2 to 13.7). I am at a loss as to why, but the range is now narrower (about 15.4 to 14.3) and more linear than before I put the stock air tube back on. Before on decel the readings would continue to jump. Now they actually hang steady or move in a linear fashion instead of "jumping". Go figure...

Since I am now convinced, thanks guys, that the Wideband is operating normally and the weather is getting right, I'm going to resume the tuning process.

Let the really stupid questions begin...