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Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Engine> Modern Electronic Engines> 6.0 lq4 getting lean codes both banks
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Topic Review (Newest First)
09-11-2019 05:32 PM
LATECH It would be a good Idea to check/clean the MAF (Mass Air Flow ) sensor,just as a routine service. see if things improve
09-11-2019 05:28 PM
LATECH All your PID values look good, except the trims.

the 2 most likely causes are

Intake leak/air leak downstream of MAF sensor (unmetered air)

or fuel pressure low.

I am still questioning the smoke test.

If you have low fuel pressure, volume will also be low

You will see the effect at WOT (wide open throttle) as the engine may surge ,lose power, or lack power for acceleration.

You can do a quick fuel pressure check. verify while under load as well ( driving /accelerating)

Go from there
09-11-2019 05:18 PM
Originally Posted by 38 old coupe View Post
I had the car smoke tested and their was no vac leaks.
Still have the lean codes I bought blue driver so I can have live data but canít post data
The injectors didnt shrink.
They arent too small.

dont make any changes until you find good evidence.

Dont change O2 sensors.That is P i ssing money away.They are obviously working if they are correcting the mixby 25%

I would question the smoke test.

2 Days ago I had a 2004 2500hd with a 6.0 Vin "U" and I smoked it.
The EGR pipe was leaking at the intake, and it was tough to seal up. I ended up doubling up O rings on it and the idle and trims Both improved.
I smoked it after I was done .It still had a tiny leak. But it was so much better and I had no more time so...out the door it went.

Lights out, trims under 5%.. Good to go.

Whwn doing the smoke test the throttle body needs to be covered/blocked to create some pressure in the intake, to exacerbate the leak /failure point

Remember I do this everyday for a living.

Now, I will look at your data log. Maybe i will see something there.
09-11-2019 12:05 PM
2001Blazer4x4 Fuel trim is the % of fuel added or subtracted from the calibration in the computer, which is experimentally required to meet the desired air/fuel ratio.

Plot both B1S1 and B2S1 in Blue Driver and hold the RPMs at 2000 on a warm engine. Do the plots cycle up and down rapidly across 0.45V? If so, the PCM is controlling the fuel mixture at a ratio it is happy with. Note - only display the O2 sensor voltage plots, as monitoring too many things greatly decreases the sampling rate for individual items (and Bluetooth devices have lower limits).

Do you have an A.I.R system to inject air into the exhaust manifolds? If so, disconnect the check valves mounted in the manifolds. If you have an EGR system, you will need to figure out how to defeat that.

Now watch both long term and short term fuel trim values as you hold the RPMS at 2000. Long term + short term FT for a given bank should be 0% Ī 10%. If not, then one of two things needs to be done.

1) Use different injectors (in your case more flow would reduce the fuel trim values)
2) Recalibrate Fuel Trim so what is observed = 0%.

So what engine and/or injectors was the PCM calibrated for? Looks like they may have missed that one in the PCM that was sold to you. I would call the PCM company and discuss your findings.
07-30-2019 07:04 AM
Just a thought

Not your application but maybe a starting point.
Your stft look right, so no vacuum leaks. The problem starts when driving. It is going lean, so your injectors need to pump more fuel into the mix. I dont know much about tuning these, only carburetor...
07-29-2019 09:51 PM
38 old coupe Yes 25% is max.
I was told to change the bosh o2s for denso or ac delco
So today I baught the denso ones and I unhooked the bat for a half hour and then installed the o2s it seemed ok tell it warmed up and went for a drive running 60 then decelerate then the ltft jump back up to plus 25 tell you give it gas again then the drop to 15 to 20percent plus.
One time I noticed the stft added 16% then the ltft went to 3.9.
I drove for a half hour and then I let it idle and then ltft went plus 25% and stft going plus 2 to plus 6 orso.
I’m sure it’s still learning but it it keeps the ltft maxes out it will set check engine light
07-29-2019 06:06 PM
lmsport both long term trims are at 25%.
Is that the max they will go?
07-29-2019 01:53 PM
Originally Posted by 38 old coupe View Post
I found out today they want 750 to tune and another 150 to put it in the Dyno Iím in the wrong field of work.
Didn't notice this when you posted. Those are somewhat steep prices for the area I'm in, but not in metropolitan NYC/northen Jersey.

The Holley Terminator X is a good option, if you can afford it, as well as Microsquirt if you can handle the basics of tuning. In a factory car, then I'm all in with using HPTuners, but in a older car that the motor has been transplanted I'm a fan of the aftermarket stuff unless your HPTuner experienced.

You mentioned you were thinking of buying it, I'd recommend against it - there is a lot of training to go along with using whereas the aftermarket stuff is designed to be user freindly.
07-28-2019 10:15 PM
38 old coupe I took pics of the data log
07-28-2019 10:13 PM
38 old coupe Here is pics
07-28-2019 10:06 PM
38 old coupe I had the car smoke tested and their was no vac leaks.
Still have the lean codes I bought blue driver so I can have live data but can’t post data
06-18-2019 08:40 PM
38 old coupe I found out today they want 750 to tune and another 150 to put it in the Dyno Iím in the wrong field of work.
06-13-2019 09:16 PM
38 old coupe Yea Iím going to get hp tuners when I can afford it.
Iíve also been debating on the Holley terminator x that self tunes.
Itís psi conversions they make harnesses and sell pcms
I couldnít find one in the wrecking yard so I baught one of theirs and they deleted vats and turned off all the sencers that throws codes that Iím not useing
06-13-2019 09:08 PM
64nailhead All kidding aside and not knowing who 'psi' is, why don't you take it to someone that can tune it? If you do, then problem solved.

Too small of injectors causing a lean code at idle is a tune issue IMO. Changing the VE table in the idle area will take approx 10 minutes with HP Tuners.
06-13-2019 01:25 PM
38 old coupe Psi programmed the wrong injectors in the first time then they redid them and still got the codes and last night I noticed I put the mass air flow flowing the wrong way. So I turned it around last night and reset the codes but I havenít ran it yet.
I called psi this am they said that it would give you lean codes or cause rich codes but more then likely lean codes

Sure hope that fixes it
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