Codes :"Bank 1 Lean Bank 2 Lean"

[65blackfleetside]

So i have both these 2 codes coming up on My Gen 3 LS . I did a fuel pressure test and it seems to be holding at 55-60 PSI.

Truck runs awesome on start up and at idle. but I do notice a stumble/ motor going lean when I put my foot into it hard. (Its a Drive by Wire)

I did a water test with a pump up sprayer all around the manifold looking for leaks. No leaks surfaced from this test with engine cold and hot.

I spoke to a local guru tuner and he seemed to think its a Mass Air flow
Location issue.

He has not tuned it yet but he explained to me on the phone that he has seen many of these LS swaps run too lean because the location and filtration of the MAF is too close to the intake. The stock location and OEM filter box do not breath as much as the OEM set ups. When you move the MAF to shorter distance- The computer gets confused and needs to be adjusted.

We will see once he plugs in his laptop and does my tune.
Has anyone else experienced this with their LS swap?

[Big Moose]

Could be an exhaust leak or faulty 02 sensors

[88Ironduke]

Agreed, make sure the exhaust system is tight. if its both banks you may7 be chasing a vacuum leak. It can be anywhere aft of the MAF sensor thru the intake, hose assemblies etc. A smoke test on the intake system might be a good course of action.

Paul

[aknovaman]

How far from the exhaust port are the 02 sensors ? If too far away, they wont heat up and properly cycle to give reliable readings to meet the criteria of Lean. Got a pic of your intake filter, maf, elbow layout ? Real numbers from a datalog will let you know whats going on. Anther factor is don't get hung up on fuel pressure like some people do. Lean conditions can be caused by, not lack of pressure but lack of volume. Hook up a hose to the fuel rail and point it into a bucket. Start the truck and make sure you have a strong flow of gas. A good system will pee a distance of about 3 feet out of the hose while the engine is running.

[First c10]

good morning, What intake tubing are you running? factory air box? After Market cold air intake? I would unplug the MAF and see if it runs better?
I ran a Cold air intake that was 4" aluminum and it was allowing more air in the engine then the MAF was reading, so the O2 read lean.
(copy of my post on a different thread)
"My sons truck had a 3-5/8" intake originally and when I put a 4" it did what you described. fuel trims out of wack and didn't idle or run well. Put a reducer around the MAF from Spectra to the stock size and everything went back to normal like flipping a switch."

[aknovaman]

Bad advise above about unplugging the MAF. That only works if the MAF is a 3 wire and a separate IAT sensor.

The truck will run like poop if you unplug the MAF. The IAT is part of the 5 wire MAF and with it unplugged, the PCM will see -40 degree air and change the air mixture and throw all the fueling even further off.

Don't do band aid fixes or experiments, get your tuner to connect his datalogger and see some real data and determine whats the real cause. He can disable the MAF and put the truck in SD to eval if the MAF is broke or if your intake MAF table or positioning needs adjusted or if the 02 sensors are cycling to produce the necessary voltage levels. That's coming from over 17 years of tuning experience.

[65blackfleetside]

Thanks for all of the input.

I will do a smoke test on the intake.

As far as the O2 sensors- The threaded ports are on the collectors approx 12" downstream from individual header tubes.

The headers are shortys

As far as the Air cleaner - Its a bullet style spectre (sp?) very similar to K&N.
The MAF is installed 6-8" downstream from intake after silicon 90.( See pict)
I am using 3"semi flexible silicone piping.

Question: I do not hear or see any noticeable exhaust leaks
IS there a way to test for exhaust leaks?

Exhaust is 2.5" pipe shorty headers with 2 in 2 out Borla muffler. Runs out the back to rear bumper.

This set up runs awesome idles perfectly- Except when I stop it.

[mongocanfly]

Did it run good at one time and then all this started or has it done this ever since the install?
If you do the smoke test be sure the fans not running...
If it hasn't been tuned since the install ,then like novaman says...start there...the tuners around here all use a base tune for the ecm unlock, so itll crank and drive,and do the final tune after you get up and running...i know my 6.0 had a base 4.8 tune in it..what a difference there was after the dyno tune..

[aknovaman]

Air coming out of the filter and making a 90 degree turn is not a good thing. I know the front end is pretty narrow but I would relocate the filter to the passenger side of the radiator to keep the airflow laminar (straight).

Also,first and foremost get a can of MAF cleaner and spray it to the point you feel its cleaned several times over.

If you discover your MAF is not accurately reading your air flow consistently, you may want to add a x type straightener before the MAF if the factory screens don't do that sufficiently.

[65blackfleetside]

Honestly I never notice it until recently. Since I just finished my build 2 months ago- I didn't want to run it hard out of the gate.
I just recently started running it a little faster

I found a you tube video of how to build a DIY smoke test machine with:
Pickle jar
soldering iron
a bicycle pump

LOL
It looks like it works like the $2000 snap on version

[aknovaman]

You are wasting your time experimenting, find someone local that can datalog it for you. GET REAL DATA.

[65blackfleetside]

I am not sure if it matters but...

It seems as if the Silicon intake Plumbing that I went with is 1" larger in diameter than what most swapers use?

I think mine is 4" most build that I see i think is 3"?

[aknovaman]

Larger tube size is not relevant. The pinch/measurement point is the maf diameter.

[First c10]

First off... A dyno tune will always be the best way to set up a swap when nothing is original and will need adjusting. On my gen IV I disconnected the MAF which put the ECM in SD mode and my lean condition went away which told me that it wasn't an vacuum leak... that's not bad advice. Anyone can tell him to drop $1K on a dyno tune.(Which is good advice but doesn't really tell the OP anything about the problem).

So after the picture of the engine bay. My comment about intake size doesn't really matter since you are not using the drop in style MAF.
A problem can be the the difference between the factory air flow path and the current path with the elbows. Nothing a good tune can't remedy, but at least you can eliminate the vacuum leak or air sucking in at an exhaust leak upstream of the O2.
Just my .02!

[aknovaman]

I would be happy to discuss you dyno tuning method for fixing an off idle stumble off line. My experience shows that dyno tuning is primarily used for optimizes wide open throttle afr. The rest of the tune must be correct before hitting the rollers.

[65blackfleetside]

UPDATE: Did a smoke test I had a leak where the MAF and 4"silicone pipe joint connect.
Tightened everything super tight- No more leak.
I erased the codes. I will test drive now and see if It still goes lean at 75%-100% throttle.
HP Tune coming in next 7 days too.

Q: where can I get the 3" black plastic pipe to redo my air intake setup. I want to run the filter all the way back to firewall and maybe move the MAF further away from intake too like in the OEM setup.I think this looks cleaner.

[mongocanfly]

Dont know about plastic but I used mandrel bent aluminum tube for mine....I got it off ebay... theres all sorts of bends,angles, and offsets
Spectre has a good assortment of tubing as well

[prodjay10]

I wonder if a muffler shop can make up something for you. Just gotta paint it after.