2002 blazer LTFT 25% STFT 54% ? Running Lean !!HELP PLEASE
#1
2002 blazer LTFT 25% STFT 54% ? Running Lean !!HELP PLEASE
Hi, i have a 2002 that is running super lean , my LTFT B1 25% and STFT B1 54% at Idle and normal numbers at Bank 2. ..my scan tool also shows P0300 and when i check, it is misfiring on cylinders 1 , 3 and 5 ... when I accelerate to 2500rpm it quickly goes to 0 then starts climbing rapidly to 54% as i hold down the accelerator. I did a fuel pressure test and it is at 55-56 psi on idle. when i open throttle goes up to about 60psi and instantly goes down to 53psi and back to 55 psi so i dont think it is fuel pressure but dont know specs so i could be wrong? the car shakes or vibrates at idle and has a smell and some smoke coming out of the pipe i believe right before the cat next to the o2 bank 2 sensor. Does anybody have an idea what is causing this ? i changed, plugs, wires, cap and rotor... I'm thinking an exhaust leak or manifold gasket leak?? not sure what to think actually !!!Thank you!
Last edited by mf2008; 05-28-2018 at 02:42 PM.
#4
You add the LTFT and STFT for a given bank. +79% on bank 1 is crazy high (adding fuel command for a perceived lean condition), never seen this before. Cylinders 1/3/5 are all three on bank one. You have extra air, restricted fuel delivery, bad sensors or a bad PCM.
So when you increase rpms the bank one total fuel trim goes to near zero and then back up to +79?
If you have scanner live data capability look and see if the O2 sensors look normal. They should oscillate between 0.3V ish and 0.8V ish every second or so. What happens if you swap the two upstream O2 sensors?
Does the truck run better initially while the live data shows the system in open loop (not using the O2 sensors yet)?
Have you done a compression test? Have you looked at your vacuum hoses? Have you addressed the lower intake manifold gaskets? How many miles?
George
So when you increase rpms the bank one total fuel trim goes to near zero and then back up to +79?
If you have scanner live data capability look and see if the O2 sensors look normal. They should oscillate between 0.3V ish and 0.8V ish every second or so. What happens if you swap the two upstream O2 sensors?
Does the truck run better initially while the live data shows the system in open loop (not using the O2 sensors yet)?
Have you done a compression test? Have you looked at your vacuum hoses? Have you addressed the lower intake manifold gaskets? How many miles?
George
Last edited by GeorgeLG; 05-28-2018 at 10:03 PM.
#5
yes it goes to 0 then quickly rises to LTFT +25% STFT +54% bank 1 ....bank 2 remains normal...o2 sensors operate normal for first 30 minutes then car starts to run rough and sensor 1 bank 1 starts to read .3v to .4v .....sensor 2 bank 1 reads .8v - .9v ... bank 2 sensor 1 fluctuates normally .3v -.8v....
hopefully i will do a compression test today... in open loop the car runs normal for first 30 minutes ...vacuum hoses look ok, have not found cracks or holes in them.. previous owner said he did the intake gaskets 3 years ago but i cant confirm that it is true.. or that it was done correctly.... miles are 190,000....car ran perfect for 3 years since the day i purchased it..
hopefully i will do a compression test today... in open loop the car runs normal for first 30 minutes ...vacuum hoses look ok, have not found cracks or holes in them.. previous owner said he did the intake gaskets 3 years ago but i cant confirm that it is true.. or that it was done correctly.... miles are 190,000....car ran perfect for 3 years since the day i purchased it..
#8
Report on the condition of the plugs after the compression test. If the injectors are the problem it would be plugged/insufficient delivery resulting in a lean condition resulting in an attempt for additional fuel delivery hence the positive fuel trim.