ltft stays at 25.0 all the time HELP
05-25-2014, 10:40 AM
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ltft stays at 25.0 all the time HELP I have a conversion on a 53 chevy. I bought a wrecked 03 avalanche drove it no codes. I used motor trans fuel pump 02 sensors new filter new -06 fuel line. Have 500 miles on conversion throws p0174 & p0171 codes every time I drive it. Sometimes they come on within 1/2 mile sometimes 25 miles. I do not have any vacume or exhaust leaks.maf clean[ same one from avalanche] only thing I can find is ltft stays at 25.0 no matter rpm or temp. Scan gauge works fine on other cars. PSI harness and tune. What next?
05-25-2014, 11:32 PM
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Lean codes and maxed + trims can also come from O2
sensors that are not working right. Do the waveforms
look sensible to you? That is, switching fast and even,
not staggering around or passed out on the floor?
sensors that are not working right. Do the waveforms
look sensible to you? That is, switching fast and even,
not staggering around or passed out on the floor?
06-07-2016, 10:37 PM
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I have the same problem as the original poster. My car is a '98 Firebird Formula M6 originally equipped with an LS1 and I replaced it with an LS6 five years ago. I've got 25K on the engine since the swap and I felt it was running great except for the darn 25.0 LTFT's. I thought they were lower at one time but I can't recall that for sure. I didn't suspect a failing fuel pump since the car didn't seem to cut out at all, but it's certainly a possibility with 150K on the chassis. My car passed the tailpipe test, but not the monitors last smog test so I've had to garage my car while I researched some solutions. I was thinking a computer tune but I better check some of the functions like fuel pressure first.
06-08-2016, 12:01 PM
#6
I have the same problem as the original poster. My car is a '98 Firebird Formula M6 originally equipped with an LS1 and I replaced it with an LS6 five years ago. I've got 25K on the engine since the swap and I felt it was running great except for the darn 25.0 LTFT's. I thought they were lower at one time but I can't recall that for sure. I didn't suspect a failing fuel pump since the car didn't seem to cut out at all, but it's certainly a possibility with 150K on the chassis. My car passed the tailpipe test, but not the monitors last smog test so I've had to garage my car while I researched some solutions. I was thinking a computer tune but I better check some of the functions like fuel pressure first.
06-08-2016, 02:56 PM
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I found the thread and your two year old comment pertinent to my situation. I'll pull out my pressure tester and go from there...
Last edited by Mr Rich; 06-08-2016 at 03:02 PM.
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06-08-2016, 03:01 PM
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I'm competent as a mechanic; I replaced the engine and trans myself and did it at 58 years of age. I've owned the car since I drove it off the lot new. The area that I may need help with is tuning since they busted my a$$ on the last smog test. I'll appreciate any help I can get. Thanks.