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PO171, PO174, PO304, and PO442 at the same time! Ideas...

djp2233

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Dallas TX
Year, Model & Trim Level
2000 XLS 4.0 SOHC
Hello. I'm new to this forum, but here goes. I have a 2000 Explorer, 4.0 SOHC with about 100,000 miles on it. About 3 months ago, I was getting codes Po171, Po174 at the same time. My truck was "chugging" at idle, so we thought it must be a miss, bad plug, etc. At the advice of a self-proclaimed mechanic, we changed the plugs and wires. They had at least 30k on them, so why not? For about a month's time, all was well. Then the CEL came on again. This time, Im getting codes PO171, PO174, PO304, and PO442.

PO171 and PO 174 suggest a rich or lean fuel/air ratio.
PO304 suggests a misfire on Cylinder #4. inspection of the plugs/wires show that they are in good condition since I recently replaced them
PO442 suggests a small leak in the EVAP system. And from what I have read, PO442, is the "mechanic's nighmare"

Just to give some insight, the vehicle "chugs" badly at start-up, and now it chugs sometimes while moving. I used some fuel injector cleaner and installed a new gas cap (the old one was, well, old), and I'm looking for some additional direction as to what all this could mean. I'm not even sure they're altogether related. Any assistance would be appreciated.
 


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montegun

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2001 explorer sport
the 171 and 174 are lean codes usually the culprit is the upper intake gasket has a leak as for as the misfire code have you checked for spark at the coil pack just because the plug looks good doesnt mean its getting the proper spark
 




djp2233

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2000 XLS 4.0 SOHC
Update. I finally got a chance to see what was going on. I decided to check the plug on Cylinder 4 since that is the code I was given. It appears that oil dripped on to cylinder 4 spark plug, gunked it all up, and caused the misfire. It was almost impossible to get that plug out, but I did with great care (after thoroughly cleaning the area around it). So I think this should solve one of my problems at least. But I know I have bigger problems to address as well!
 




Zach Everlast

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99 ford explorer sport
po442 is normally an evaporation error such as a hose leak or something small like that. mine has it all the time with nothing major seeming wrong, i just clear the code and keep driving.
 




drdoom

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2005 Eddie Bauer 4.6L 4X4
I would be doing a run-up on the EVAP system, tracing all lines & connections. You have a leak there I think.
 




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