Misfire issue on stock 4.8 with external FP setup.
01-20-2017, 06:10 PM
#11
No real change with new Alt, still missing randomly and not setting P0300 code. So I decided to add another 4ga ground while double checking the ground to the block. This also did not net any change.
Will check spark once my checker arrives. New alt is also getting pretty hot, presumably because it is trying to charge what was a dead battery... but not really sure.
Will check spark once my checker arrives. New alt is also getting pretty hot, presumably because it is trying to charge what was a dead battery... but not really sure.
01-24-2017, 06:26 PM
#12
Interesting tidbit tonight. When I rev the engine to right around 2k, it then drops a cylinder... But if I rev it and hold at right around 3k, it stays solid. So it is breaking up much more right around 2k. You can hear/feel it literally drop a cylinder at that rpm. Also unplugged the MAF sensor and it ran basically identical as plugged in.
Obviously when it is just at idle and has the random missing, you can tell it isnt running 100%, but I think the 2k drop might be something to help diagnose?? Thoughts?
My new crank sensor and spark checker showed up tonight, will try to get them installed this weekend to see if anything changes. If no change, I might swap in my 60# siemens to rule out injectors.
Obviously when it is just at idle and has the random missing, you can tell it isnt running 100%, but I think the 2k drop might be something to help diagnose?? Thoughts?
My new crank sensor and spark checker showed up tonight, will try to get them installed this weekend to see if anything changes. If no change, I might swap in my 60# siemens to rule out injectors.
Last edited by xxch0dyxx; 01-24-2017 at 06:33 PM.
01-29-2017, 12:08 PM
#15
And the plot thickens...
Was out scanning and messing with closed loop/trims. I wanted to leave the truck running long enough to hit 200* to make sure my e-fans would turn on like they should (never verified after adding them and tuning). All worked as planned.
Put the truck in gear and footbraked it to see if the missing remained, it did not. So I took it for a short drive, everything felt and acted normal without misfiring. Park it in driveway, and have misfires again. So it is only when the truck is in Park/Neutral that it is having bad misfires. Not really sure what this tells me, thoughts?
Here is the log for your viewing pleasure. I am....perplexed
Was out scanning and messing with closed loop/trims. I wanted to leave the truck running long enough to hit 200* to make sure my e-fans would turn on like they should (never verified after adding them and tuning). All worked as planned.
Put the truck in gear and footbraked it to see if the missing remained, it did not. So I took it for a short drive, everything felt and acted normal without misfiring. Park it in driveway, and have misfires again. So it is only when the truck is in Park/Neutral that it is having bad misfires. Not really sure what this tells me, thoughts?
Here is the log for your viewing pleasure. I am....perplexed
02-03-2017, 03:40 PM
#16
Once the truck warms up, misfires now pretty much go away. If I try to drive it before it is warmed up, it has a similar misfire problem. Once warmed up, drive nearly perfectly.
However, now it appears to be a lean condition like my FPR isnt doing its job. I do not have a FP gauge to watch while driving, so I am going to go out and watch while the wife revs the engine. See scan:
However, now it appears to be a lean condition like my FPR isnt doing its job. I do not have a FP gauge to watch while driving, so I am going to go out and watch while the wife revs the engine. See scan:
03-15-2017, 06:58 PM
#17
Just to close this thread out... After the alternator install, and time on the road, the issues have all but went away. Cold start is a bit rough, but no longer missing at all. I just did a MAF tune on the truck, and runs solid once it reaches temp. Random misfire might happen once or twice each log. I believe a combo of my Alt going bad, as well as low battery voltage from not driving/running long enough to charge the battery was the culprit.