NEED HELP BAD 5.3in a 1953 3100 throws lean codes every time you drive it. have put 4500 miles on it this way done every thing anybody has said new parts/starting fluid propane water smoke stil throws both codes every time you drive it could it be in the tune HELP 72 years old don"t have a lot of time left THANKS

 

If you have a MAF, clean it, check for fuel system restrictions (dirty fuel filter...) and make sure your PCV connections are tight.
Any air leaking in NOT seen by the MAF will lean you out.
BTW, I'm 71. Unless there are health issues, you have a ways to go yet...

 

Cleaned tried new one checked pcv it is tight

 

What type of throttle body? Several-but not all-of the after-market throttle bodies-even brand new ones-are HUGE vacuum leaks! If you have smoked it and cannot find a leak on the TOP side of the engine.. what about exhaust leaks? Where are your O2 sensors located? How far are they away from the engine? is there any chance you have any air leaks between the cylinder head and where the O2 sensors are located? Have Hp Tuners? If so, can you do a log of you driving the car and let's see what the fuel trims are doing..

 

Early LM7 5.3’s with the red O-Ring intake gaskets were prone to not sealing and causing lean codes. You may have already covered this but, thought I would mention.

 

A log would help us diagnose if he actually has a vacuum leak.. It would show us that the fuel trims would be HIGH on which bank, or both banks, and he would know which direction to look from there.

Check the MAP sensor.. Seems to be a few people have found loose fitting map sensors on the intake that is allowing a leak around the sensor.. I know a smoke test should have shown that... but... it does not hurt to check again. what about a leaking brake master power diaphragm? I would unplug the brake booster and then plug the end of the hose to seal it up, and with a scanner hooked up just watch to see if the fuel trims start correcting.

 

2003 engine factory Z06 exhaust manifolds they have the 02 sensors in them replaced intake and exhaust gaskets stock intake manifold long term fuel trims stay about +25 sometimes they might drop 1 or 2 numbers no hp tuner just code reader cleared codes today short trip 6 miles threw 2 codes for each bank alwayes throws codes on both banks

 

Truck has done this since day 1 has never thrown any other codes truck runs good no other problems

 

Where are you located at not2oldchevy?

 

If you are clearing the codes and they keep coming back, you might want to operate under the assumption that the motor really IS running exceptionally lean. I would try and resolve this issue before you put too many more miles on the motor. Lean conditions make for bad things happening in the motor. Think piston crown material depositing onto the spark plug electrode... Or, ring lands deciding they want to change location from where they are supposed to be, to somewhere else... Blown head gaskets. All very bad things. I would not risk blowing the engine up driving it until you can find resolution on this matter... But if you must drive it, until you figure it out-I would NOT be giving it a lot of gas, stomping the gas pedal, flooring it, or whatever other way you want to describe hammering down on the gas pedal.

As Che70velle asks.... Where do you live? If you are close to me, I've got HP tuners and I can take a look at it for you to try and help you figure it out.

 

what are the exact codes ????

 

All these comments, and nobody has asked about the most obvious question. What is the fuel pressure? Does the OP even know that it should be 58psi for LS based fuel injection?

 

Live in east tn 50 lb pressure give it gas it will go to 58 goes back to 50 when you let off the gas tried 3 diffrent fpr all did the same unhook the vaccum line to fpr it goes to 58 with all 3 fpr 2003 engine with return system

 

Live in east tn Fuel pressure is 50lb give it gas it will go to 58 unhook the vaccum line to fpr it goes to 58 tried 3 diffrent fpr they do the same cannot find one that will hold 58 all the time new fuel pump also 2003 engine with return system p0171 p0174 codes

 

Will it hurt to run it with the vaccum plugged it will have 58lb with it unhooked

 

Lots of good advice here...but, you're just shooting in the dark till you get some kind of scan tool so we can see what the actual o2 readings are doing...

 

02 reading within range just plugged vaccum to fpr 60lb with fpr unhooked stays 60 on any throttle new ltft at idle +18 & +17.2 1050 rpm +15.6 & +15.6 2200 rpm +18 & +19 will it hurt anything to run it plugged off ?

 

Read post # 14.

 

Okay.. there is so much ground to cover... The FP should be fine where it's at.. This 5.3.. what year is it? Did you use the computer that was originally paired with that 5.3 from NEW? Has anyone modified the tune in any way? Have you changed anything on the motor-anything at all? This is a situation where if the car was in front of me-I'd be on top of the problem in under an hour, and fixed by the next day.. over the internet is like trying to talk a blind guy through painting the Mona Lisa...

 

2003 avalanche engine trans computer psi harness psi flashed computer I marked computer before I sent it to psi so I know it is the seme only thing changed is early C5 exhaust manifolds they have 02 sensor outlets in them 2 1/2" exhaust and diffrent air filter