02 explorer 4.0 sohc. Codes:P171,174 &303

[StxHammer]

Over the past four days I've been getting a rough idle and check engine light with those codes. I've replaced the spark plugs and will be replacing the spark plug wires. Could this be the dreaded PCV elbow and if so where is it located. Truck has 161,000 miles on it. Thank you in advance.

 

[Drewmcg]

On my '02 XLS the PCV elbow is on the drivers side rear of the engine, running between the left head and the left valve cover. Its easy to remove by sandwiching your hand in between the top rear of the valve cover and the firewall. I have not heard that this is a particularly common fault point, however.

I'd suggest having an independent mechanic do a smoke test and look for the vacuum leak that probably is causing your leak codes, if you can't find an obvious source via detailed visual inspection.