t_ahan
Full Access Member
Hello every1. I finally got around to firing up my rebuilt 6.0 lq4 after having it bored for new pistons .
Upon first start I was happy to hear the motor sounding smooth but had a manifold leak. I ran it for no more than 2min. Fixed the exhaust leak , fired it back up and let it run alil longer and quickly realized I had misfires. Hooked my modis up and found p0300 and moved on to misfire counter where I found bank 2 ringing up counts on cyl4,6,8...cyl4 had 46 misfires and 154 in history cyl6 had 132 and 151 history cyl8 had 18 and 29 in the history.
I checked the spark with a spark tester n saw them all firing, checked all my connectors and connections and main grounds, all were good. Swapped coils plugs and wires with known good cylinders after verifying and inspecting/testing all components.
Noid lighted injectors and verified I had good commands but cyl6 made no change whether it was connected or not so I knew it was a dead mis in that cyl, then did injector balance and found fuel pressure and injectors to be good!?
Pulled the plugs again and removed the valve cover to chk springs,rockers, push rods while I did the compression test and a consistant 190psi in every cyl every time (which was very good news!) Stuck my bore scope in to look at cyl walls n valves n the look normal for a motor that has only ran for 10min....but in cyl6 I noticed a burnt\charred spot on the piston where the intake valve is, from what I think is unburned fuel?
I sprayed around all the usual intake leak areas and all the others and found I have no air leaks.
I checked all my parameters 02, maf, map, and all the others and couldnt find anything .checked alt output, good! Since the motor has never gotten to close loop not much can be learned there so I moved on to testing sensors (voltage, frequency, resistance tests) found nothing!
I kno I should do a crank re learn but cant cuz the misfire and I dont have p0315 so im assuming the pcm has it stored.
Im down to pullin injectors to verify spray patterns/known good cyl swap and other than that im not sure where else to go? Im running out of things to test and all ive learned is what it isnt..I am reaching out to all of u to get my brain cells workin cuz its burning me out and im sure its something simple that I am missing so plz help me stay sharp and throw ur 2cents my way! Thanks
I can give motor specs if that helps but its really a mild build and should be the same as anyother misfire diag.
Upon first start I was happy to hear the motor sounding smooth but had a manifold leak. I ran it for no more than 2min. Fixed the exhaust leak , fired it back up and let it run alil longer and quickly realized I had misfires. Hooked my modis up and found p0300 and moved on to misfire counter where I found bank 2 ringing up counts on cyl4,6,8...cyl4 had 46 misfires and 154 in history cyl6 had 132 and 151 history cyl8 had 18 and 29 in the history.
I checked the spark with a spark tester n saw them all firing, checked all my connectors and connections and main grounds, all were good. Swapped coils plugs and wires with known good cylinders after verifying and inspecting/testing all components.
Noid lighted injectors and verified I had good commands but cyl6 made no change whether it was connected or not so I knew it was a dead mis in that cyl, then did injector balance and found fuel pressure and injectors to be good!?
Pulled the plugs again and removed the valve cover to chk springs,rockers, push rods while I did the compression test and a consistant 190psi in every cyl every time (which was very good news!) Stuck my bore scope in to look at cyl walls n valves n the look normal for a motor that has only ran for 10min....but in cyl6 I noticed a burnt\charred spot on the piston where the intake valve is, from what I think is unburned fuel?
I sprayed around all the usual intake leak areas and all the others and found I have no air leaks.
I checked all my parameters 02, maf, map, and all the others and couldnt find anything .checked alt output, good! Since the motor has never gotten to close loop not much can be learned there so I moved on to testing sensors (voltage, frequency, resistance tests) found nothing!
I kno I should do a crank re learn but cant cuz the misfire and I dont have p0315 so im assuming the pcm has it stored.
Im down to pullin injectors to verify spray patterns/known good cyl swap and other than that im not sure where else to go? Im running out of things to test and all ive learned is what it isnt..I am reaching out to all of u to get my brain cells workin cuz its burning me out and im sure its something simple that I am missing so plz help me stay sharp and throw ur 2cents my way! Thanks
I can give motor specs if that helps but its really a mild build and should be the same as anyother misfire diag.
