rgorke
Dedicated LVC Member
Thanks again to Joe for pointing me, and countless others, to misfires. I finally figured out how to check for misfires using my iPhone app diagnostic tools. And before I get yelled at: 04 V8 with all the bells and whistles, 217k miles. All plastics changed out and new coils in mid 2016. Been getting P0171 and P0174 and occasional P2195 and P2197 codes.
It appears that for the first 15-20 mins of the car running I get 1) high positive short term fuel trims and high (and erratic) long term fuel trims and 2) appear to have some misfires that look like they go away after complete warm up. Graph shows 6 misfires that were steadily going down. (see picture)
Also, the fuel trims are higher during idle and come down at higher RPM. So...
1) I have changed vacuum hoses and can't find any, even during this "warm up" period.
2) Changed fuel filter and run half a dozen or so tank fulls of injector cleaner.
Hypothesis:
With the misfires, could it possibly be from some oil on the plugs and then the oil gets burned off after 15-20 mins? I have read over filling oil can cause misfiring. Not that I specifically recall overfilling but it could be possible. Again the coils are only 18 months old and replaced by Lincoln dealership. Would cleaning and checking gap on plugs be a prudent step?
Any other specific tests? I have never had any misfire codes.
My other hypothesis is a slight exhaust leak. I have a video that shows some slight soot on exhaust manifold gasket.
So, any thoughts? How do misfires cause lean codes?
Thanks again,
Roger
It appears that for the first 15-20 mins of the car running I get 1) high positive short term fuel trims and high (and erratic) long term fuel trims and 2) appear to have some misfires that look like they go away after complete warm up. Graph shows 6 misfires that were steadily going down. (see picture)
Also, the fuel trims are higher during idle and come down at higher RPM. So...
1) I have changed vacuum hoses and can't find any, even during this "warm up" period.
2) Changed fuel filter and run half a dozen or so tank fulls of injector cleaner.
Hypothesis:
With the misfires, could it possibly be from some oil on the plugs and then the oil gets burned off after 15-20 mins? I have read over filling oil can cause misfiring. Not that I specifically recall overfilling but it could be possible. Again the coils are only 18 months old and replaced by Lincoln dealership. Would cleaning and checking gap on plugs be a prudent step?
Any other specific tests? I have never had any misfire codes.
My other hypothesis is a slight exhaust leak. I have a video that shows some slight soot on exhaust manifold gasket.
So, any thoughts? How do misfires cause lean codes?
Thanks again,
Roger