Help with ltft at 25.0

[not2oldchevy]

I have a 53 with a 5.3/4l60. Anything over idle I get ltft of 25.0. Engine transmission computer fuel pump all from 2003 avalanche that I drove with no codes. I have 700 miles on the conversion and get 0171&o174 codes every time I drive it. No vacuum or exhaust leaks. New fuel pump new tank new filter new 6an fuel line new fuel pressure regulator with no change. Fuel pressure is 50lbs with old and new parts. All fp regulators I have found foe this 2003 avalanche advertise 50lbs. I tried one for a 2002 suburban that was 58lbs but it would not fit. I also have a 1999 Z71 5.3 and a 2004 Z71 both hold 50lbs fp with no codes. I have no idea what to do next. Go POSTAL ????

[akdg87]

What did you do with the Evap line from the gas tank going into the intake?
o2 sensors in factory locations?
Check for leaks on intake tubing? Any leaks between the MAF and throttle body will cause this.
Do you have all the PCV lines hooked properly up as well?

[First c10]

What filter and intake tube are you using? I used a spectra cold air intake and had the same issue.
I disconnected my MAF and the ltft went to normal. +/-3

[BR3W CITY]

Does fp stay the same when running, or does it spike or drop? You could have a restriction on the fuel system, or stuck injectors. What are you running for an intake, where is your maf?

How was it tuned?

[not2oldchevy]

Evap plugged same o2 sensors with engine in c5 corvette manifolds no intake tube leaks same maf with engine. I have got spectra filter that was on a cold air intake that was on same avalanche that every thing else but the c5 manifolds came off of. Fuel pressure stays at 50lbs all the time. LTRT is about 18 at idle. Will check maf.

[not2oldchevy]

Mail order tune from PSI with harness. MAF is .70 at idle & 2.2 at about 1500rpm MAP 9.2 & 7.7. Unplugged maf did not change tried different filter no change.

[not2oldchevy]

Anybody????

[cableguy0]

Either your tune has a serious problem or you have a major vacuum leak. Fuel trim that lean could cause engine damage from pinging and actually running hot.

[not2oldchevy]

I have used starter fluid on every part of the engine no leaks anywhere. Has never had a ping runs at 195 to185 with 185 tstat.

[cableguy0]

Is there a place local to you that has tuning capabilities? A good tuning guy might be able to see the problem almost instantly.

[First c10]

N2oc
I am no way the man for this. But I had the same issues super73 helped me as he is a tuner and lives 1 hr or so away from me.
What we did was disconnect the yellow wire on my blade style MAF. He did tune the engine and trans and then disabled the MAF in the tune. I am talking about the MAF part not the intake temp part. Since then my numbers have been good...also,he ran the wide band o2 sensor on it and dialed the AFM as we road Dyno'd it. I am probably missing 90% of what he did. But hope this helps!!! Probably best to take to someone after you have done some research. Good luck

[Super73]

Firstc10, glad it is running good.


Not2...I am surprised that that truck is supposed to be 50psi pressure, doesn't sound right to me.

Pull out the single wire for the maf from with the pcm or maf it self. You will have a ses light but it will put you in speed density mode. Go drive the truck gently for an hour or so and the take a reading on you ltft's. You have to understand that ltft's are really your stft's that are averaged over time so it takes a little driving for them to average the other direction.

If that does not show some results, then either the fuel pressure has it all messed up or the VE table in the tune is off.

[BR3W CITY]

Originally Posted by Super73

Not2...I am surprised that that truck is supposed to be 50psi pressure, doesn't sound right to me.

.

I thought that too, but it turns out the Avalanche is the oddest duck in the LS family (next to the ssr). Early Av's used a regular "Truck style" FPR that was only set at 48-52psi....but actually lists a different part # if you have a manual or auto trans....
...and then they moved the FPR into the fuel sending unit the years after. So go figure.

[not2oldchevy]

Originally Posted by BR3W CITY

I thought that too, but it turns out the Avalanche is the oddest duck in the LS family (next to the ssr). Early Av's used a regular "Truck style" FPR that was only set at 48-52psi....but actually lists a different part # if you have a manual or auto trans....
...and then they moved the FPR into the fuel sending unit the years after. So go figure.

I have tried the 58lb fpr and none will fit.

[dayj1]

Originally Posted by not2oldchevy

I have a 53 with a 5.3/4l60. Anything over idle I get ltft of 25.0. Engine transmission computer fuel pump all from 2003 avalanche that I drove with no codes. I have 700 miles on the conversion and get 0171&o174 codes every time I drive it. No vacuum or exhaust leaks. New fuel pump new tank new filter new 6an fuel line new fuel pressure regulator with no change. Fuel pressure is 50lbs with old and new parts. All fp regulators I have found foe this 2003 avalanche advertise 50lbs. I tried one for a 2002 suburban that was 58lbs but it would not fit. I also have a 1999 Z71 5.3 and a 2004 Z71 both hold 50lbs fp with no codes. I have no idea what to do next. Go POSTAL ????

Random thought: Is the PCV "fresh-air" line on the passenger's valve cover connected after the MAF?

Also, you may want to check that your tuner didn't flash a "canned tune" for you that has injector data for a fuel pressure of 58. As you've probably already guessed that would cause your problem as well.

[BR3W CITY]

Originally Posted by not2oldchevy

I have tried the 58lb fpr and none will fit.

No I'm agreeing with your original thought of 50psi. Thats the correct FPR, it just happens to be very unusual, since that design wasn't really used on many engines compared to the 58psi unit.

[not2oldchevy]

Originally Posted by dayj1

Random thought: Is the PCV "fresh-air" line on the passenger's valve cover connected after the MAF?

Also, you may want to check that your tuner didn't flash a "canned tune" for you that has injector data for a fuel pressure of 58. As you've probably already guessed that would cause your problem as well.

PCV fresh-air is where it is supposed to be.

[Super73]

I think whabrew is asking is, is there any incoming air supplied to the motor after the maf. Ie, some throttle bodies have a hook up for a valve cover. If everything is closed in the crank case including valve covers, this would pull a slight vacuum in the crank case. If one valve cover had the tube to the throttle body and the other is vented to the atmosphere, you will be pulling unmetered air in to the motor that is not being read by the maf.

[not2oldchevy]

Hose from passenger side valve cover to throttle body, everything is the same as it was in the avalanche.

[not2oldchevy]

FIXED took out the ses light bulb and put the scan tool on the shelf.

[BR3W CITY]

Originally Posted by not2oldchevy

FIXED took out the ses light bulb and put the scan tool on the shelf.

If your actually hitting ltft's near 25 still....all you did is pull the pin on a handgrenade.

[not2oldchevy]

Originally Posted by BR3W CITY

If your actually hitting ltft's near 25 still....all you did is pull the pin on a handgrenade.

Still at 25 right off idle but I have run out of options. I live out in the country with no tuners anywhere close.

[BR3W CITY]

There are 2-3 in the Memphis area I've heard of. Thats East TN isn't it? I only know TN from portions of 65 in the Nashville area, never spent time east.

[Super73]

What year pcm?

[not2oldchevy]

Originally Posted by BR3W CITY

There are 2-3 in the Memphis area I've heard of. Thats East TN isn't it? I only know TN from portions of 65 in the Nashville area, never spent time east.

I am on the other end of the state from Memphis.