2003 Ford Explorer Sport Trac

My sport trac started idling rough about two months ago, and then the check engine light came on.

I had it checked out and it is apparently running lean on both P071 and P074.

I was told this could be the fuel injectors; the fuel filter; the MAF sensor; a vacuum leak; a bad O2 sensor; or a bad fuel pump.

I have cleaned the MAF sensor, changed the fuel filter,and added fuel injector cleaner to gas tank twice now, with no effect.

My next task, is to find out if there is a vacuum leak, unless you have some other ideas.

Of course what is the best way to find a vacuum leak?

I assume you mean P0171 and P0174.

Start by listening carefully for any hissing or sizzle etc. Then disconnect and plug (or pinch off) vacuum lines one by one. Don’t forget the brake booster and the hose to the PCV valve. Spray some carb cleaner or canned air or use your breath with a hose around where the intake manifold joins the cylinder head, also around tubing from throttle body to intake manifold.

Test fuel pressure, but I doubt that’s a problem only at idle.

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