I have a 98 explorer with a 4.0l, i have a check engine light after reading what codes i had they were po 171, 174, 455, i also have po 305 ( #5 misfire ) which a change in the spark plug should correct that, but i am wondering if the other three 171, 174, 455 are related to each other or if the are separate issues. any help i can get would be great.. thanks

 

The P0305, may be connected to the P0171 and P0174 (misfire caused by lean mixture), The P0455 is an evap leak (large) which could contribute to the lean mixture...... I would chase the evap leak first... Philip

 

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P0171 & P0174 4.0L SOHC's Sport/Sport Trac - Ford Explorer Ranger Enthusiasts "Serious Explorations"®

 

His1998 would be comparable to the 2001 Job 1 Sport Tracs and not have that problematic elbow. The pcv valve could still be an issue there though.