Lift +25??

[Mattver]

U7198 V9xxx 2000 yukon XL 5.3
Just got the predator today. Never would have made the leap without all the great info here on the forum.
I installed CAI & Catback Flowmaster about 1 yr ago?
87 Tune and logged data....The Long term Bank 1&2 both show +25 and program says to adj -26
Does this sound right?

Thanks

[Grumpy_Aero_Guy]

U7198 V9xxx 2000 yukon XL 5.3
Just got the predator today. Never would have made the leap without all the great info here on the forum.
I installed CAI & Catback Flowmaster about 1 yr ago?
87 Tune and logged data....The Long term Bank 1&2 both show +25 and program says to adj -26
Does this sound right?

Thanks

Your engine is running lean...(waaaaay lean, it seems). Control is adding lots of fuel to get you stoichiometric.

1) no "trick" or "walk on water" MAFs, no mods to the MAF sensor, etc., etc.???????

2)check your intake system for leaks and correct, i/a.

3)check your exhaust system for leaks and correct, i/a.

Re-Log, and see where you are.

Also, post your log as a csv, and I can take a look. Not unheard of, but unusual. Usually indicates an undetected leak.

[06MonteSS]

yeah man, that is NOT correct at all... something is amiss....

and like grumpy said above... you don't have an aftermarket MAF, do ya?

check cai/intake for any leaks, make sure all hoses/clamps are TIGHT... and same with exhaust, make sure no leaks anywhere and that everything is TIGHT...

do NOT adjust your slope to -26... +25 is GM's fuel trim limit for lean... you should be getting a trouble code thrown and CEL on your dash if it's THAT far off...

something is not right with your truck...

[Mattver]

No special MAF...only CAI and CatBack Muffler
Will check for leaks
Here is the file

Thanks

[06MonteSS]

yeah, they're pegged at 25... something's not right...

could be bad/shot O2 sensors as well...

[Mattver]

Will check for leaks....how do I check O2 sensors or do I have to take to a shop?

[RedJewel2SS]

log O2 sensor voltage. if they are changing a lot then they are ok, if it stays at a constant, chances are they are bad.

visual check of them: just unscrew and unplug them and check for any charring, give them a good clean before reinstalling them.

[Mattver]

UpDate...Tightened Intake clamps no change
No dash lights but did find code P0137 &P0157 "low O2 volt Bank 1 and Bank 2 Position 2)
I believe this is the rear sensors.
1)Do I just replace them?
2)Replace all 4?
3) More trouble shooting 1st?
About 95K miles

Thanks t everyone for the help!!

[Mattver]

Also...in the realtime monitoring all O2 voltages would change but rear sensors in a narrower range

[Mattver]

OK,still trying to understand why my Yukon is +25 lift on 87 tune
replaced 2 rear O2 sensors. Had code P0137 &P0157 No Change
Reinstalled Factory Tune. Do I have to drive 25-50 miles to re-look at lift?
Where should the typical lift be on a factory tune? 0 (+/- 5%)?
I have checked everything I can think of on intake and exhaust without having to dig in too deep.
What next....have shop see if everything is within factory specs on their scope?

Any help would be appreciated guys. Thanks

[Grumpy_Aero_Guy]

OK,still trying to understand why my Yukon is +25 lift on 87 tune
replaced 2 rear O2 sensors. Had code P0137 &P0157 No Change
Reinstalled Factory Tune. Do I have to drive 25-50 miles to re-look at lift?
Where should the typical lift be on a factory tune? 0 (+/- 5%)?
I have checked everything I can think of on intake and exhaust without having to dig in too deep.
What next....have shop see if everything is within factory specs on their scope?

Any help would be appreciated guys. Thanks

hmmmmmmmm...

If it were ME, I would probably restore the stock tune, , let it settle in (20-30 miles), scan for codes and if there are any, then see what is needed to correct them. If you are SURE you have no leaks ..... (?)

My experience with trucks is that LTFTs out of the box can be +/- 5-8% (usually positive), some better, a few worse. Certainly NOT +/-25%.

Something's up. Sorry, got nuthin more.

[Mattver]

Hi Grumpy....after replacing the O2 sensors the error code has not come back yet but only got 40 miles. I did reinstall factory tune. I will put some miles on it tomorrow and check for codes and LIFT #s.
I have reached my limit for finding leaks.

BTY, what's your aero interest(in you name)? Just wondering...I fly and build airplanes for a living...if that's what you can call it in this economy. Thanks again

[Grumpy_Aero_Guy]

pm sent

[06MonteSS]

Grumpy FTW!!!!!

his nickname is The PatentMaster

[Mattver]

Hi Guys....Repositioned the CAI and cleaned MAF.
On Factory Tune the LIFT has settled down to about +19%
I have checked induction system over for leaks to the best of my ability. Checked torque,leak tested the intake by spraying carb cleaner around the intake manifold gaskets and fittings at idle with no idle change.
Could the CAI be causing this because its breathing easier, or should the computer compensate and get closer to 0%?
Do you think I should take to a shop for more trouble shooting. It seems to run good but maybe there is still a problem?
Suggestions?