99 Expd. 4.6L Check Engine Light/lossing power HELP!!!
I have a 99 Expeidition with 140,000+ miles on it. It recently started to stall and jump at low idle speeds. I replaced the sparkplugs and wires, and the fuel filter thinking that was the problem....low and behold, it turned out that a vacume hose had developed a hole just above the PCV valve (which was not working 100%) which was causing a loss of vacume in the Emizzions/engine control system (much thanks to an eariler post on this web site for the help). After fixing 3 inches of hose things were great.
This fix worked for a little while but the check engine light came back on with several diffrent codes. To say the least, I have cleaned the IAT sensor and the MAF sensor, replaced the EGR valve, replaced the DPFE sensor (after cleaning it and finding an increase in performance that only went away after a day).
Long story short, I now have a check engine code P0401 that won't go away. A few days ago I changed the oil in the car and the check engine light went away with a noticable increase in engine proformence (good gas miliage and good exceleration) (note here: It seemed like only about 4 qts. of oil drained out instead of the 6 qt. that should be there. ???could there be an oil leak into the engine that is affecting an emissions sensor???). But the light came back on after the oil change and the poor proformence is back (low gas milage and slugush exeleration). Does anyone have any ideas about how to get this solved?????
The only thing I can think of is that maybe the EGR vacuum regulator (which controls the EGR) is not working. But that is the last sensor of many that I have relpaced already. Please HELP!!!! Thanks in advance.