Randy WS6

iTrader: (69)

Can any one help me , On a hard run my AFR is starting out at (12.5 OL) and all of a sudden it jumps to (19.5 OL)with no KR's, it just started doing this the other day, before that every thing was working fine as far as i could tell ,I'm trying to tune my self and don't know a lot about it, but I'm trying to learn,The motor is a LS2 418 cid.Ive changed the fuel filter and the fuel pressure is dropping down around 50psi i have a 255 fuel pump. You can see it in my log file at the end of the logging and i put my Tune files also if any body can help me with the tune ,i know there are mistakes but I'm learning. and this problem is with out nitrous

The engine is a LS2 418cid ,4.100"stroke 6.125" rods 4.30" bore ,Ross 4.030" flat top nitrous pistons with 6cc valve reliefs: ported Fast 90mm int. Holley 90mm TB, SVO 42lbs. injectors, Dart Pro1 CNCed from Texas Speed ,2.100" int, 1.60"ext. ,59cc chambers, 255cc int runners, Crane 250/266-650"/650"-112.,electric water pump 250 Pro Fogger N.O.S. and all the rest of goodies. You can see it in my Sig if you like.

EFI Live Log file=
http://forum.efilive.com/attachment....1&d=1180621552

EFI Live Tune File=
http://forum.efilive.com/attachment....3&d=1180622438

Frost

iTrader: (45)

If this is a new thing (if it USED to work right) and you have tried your tune that USED to work then I'd be looking at physical issues on the car.

Randy WS6

iTrader: (69)

I ve tryed the original tune and even riched the PE table and steal dose the same thing ,do you think its the PLX WB sensor its self ?

Frost

iTrader: (45)

I don't know much about that wideband... I DO know that if you are getting REAL misfires that the un-burned fresh-air that is passed out of the exhaust can appear to be a false lean. What do your plug look like? Do you FEEL any misfiring?

Randy WS6

iTrader: (69)

unburned fresh air ,you lost me ,i thought it would be unburned fuel, if it was a misfire unless i have bad injectors to cause a lean condition misfire.But i dont feel any misfire on top end and i dont see any misfire in the EFI live log file in my first post but i may be missing it some were.

jimmyblue

iTrader: (11)

Oxygen sensor sees the unused oxygen and a misfired exhaust
pulse has plenty, looks lean.

Plug gap, insulation fault in coil or wires, etc. can make a spark
fail and something marginal, may fail only at high cylinder pressures.
Or put a weak enough spark that the burn only partially gets done
in the timeavailable at higher RPM.

Even stock F-body tunes do not have any misfire checking at high
RPM. So it probably won't be any help for a high RPM miss or
weakness.

Dropping from 58 to 50PSI ought to give you about an 8% lean
error. This element seems not enough to produce the problem
(magnitude).

A MAF table error or a corruption of the MAF signal (like harness
EMI or a system electrical problem) could give you this on a MAF
tune, and look for kooky features of the VE table for a speed
density setup. I would expect true short fuel to show you KR
but way lean like that, might just not fire fast enough to knock.

Frost

iTrader: (45)

well both are present, but the WB reads oxygen not fuel.

Randy WS6

iTrader: (69)

I found it ,it was a faulty WB O2 sensor. Thanks for all the help and information.

Billiumss

iTrader: (11)

That was going to be my guess.

Mine did that before when you went WOT, worked down low but as the rpm got higher it got leaner and then went right to 19+AF. Then it got worse, the hotter it got (sat in traffic or more WOT blasts) the more it went to 19+ AF.

Frost

iTrader: (45)

If my WB did that at WOT I'd have to change my pants

edcmat-l1

iTrader: (10)

If its going that lean for real, the narrow band is going to drop like a rock. If your narrow band stays in the .900v range, and the WB shoots up, its a WB failure.

txhorns281

iTrader: (12)

Innovate controllers with Bosch sensors do the same thing when they are nearing their end... lol first time I saw it my heart definitely sunk....

Randy WS6

iTrader: (69)

I was a Bosch WB sensor, been in for around two mouths ,And when I noticed the 19.5 dearing the run i could have reached down and jerked the gas pedal out of the floor to shut down the run

MavrikTA

iTrader: (27)

What kind of sensor does the AEM WB run? Mine is, and has been doing the same sort of thing. This makes alot of sense!

Randy WS6

iTrader: (69)

I dont know. Mine a PLX WB

http://www.plxdevices.com/products/a.../BoschLSU4.jpg

Doc

iTrader: (9)

Think of it this way...Take an Edison light bulb (while you still can) and sprinkle some specs of moisture on it...Might not go all bad right away but it will crack. Now, imagine your pump cell under the metal helmet of the LSU4 in the exhaust track, with the little holes, moisture, naturally present can get in there and cause a slight crack that will only tell on it'self at high exhaust pressure, i.e. WOT thus, why it stills reads fine at Stoich but deadly lean at WOT.

Tail chasing, ain't it fun?

Frost

iTrader: (45)

Come to think of it I've seen this same behavior from them when they are just fouled up from being in a rich-*** pipe. We pulled the O2 and burned the end with a torch to get it clean and it was right back to business as usual

Randy WS6

iTrader: (69)

When i pulled mine it was dark tan, With no sut on it at all,so i guess ir was cracked ,install a new one and every thing is normal now ,with AFR at WOT is 12.5