I have multiple codes that have shown up, a little history, I purchased vehicle in Atlanta and now am in Colorado @ 6600'

P300 shows up. At idle it hunts and misses but at higher rpm's I do not notice any loss of power.

P1131 and p1151 lack of ho2s switch sensor indicates lean.

Are these 3 codes related and where should I start?

Any help appreciated

Thanks guys.

 

Moved to Expedition forum

 

Since the problem is occurring mainly at idle and then disappears at higher rpms indicates there may be a vacuum leak allowing unmetered air to enter the engine and cause the lean condition. This affects the air/fuel mixture and could result in the random misfire code as well.

I would suggest looking around the engine bay for vacuum leaks; check for any loose/damaged hoses or vacuum lines, or any cracks in the intake tube past the MAF, anywhere there could be a loss of vacuum. You could also check for leaks by spraying some throttle cleaner near hoses and intake manifold and listening for a change in rpm.

 

There are rubber gaskets on the throttle body that can leak, these are easy to replace and inspect.

 

At the back center of the intake is a rubber elbow for the PCV system. This elbow fails and causes a large vacuum leak as well as lean codes. I'd start there since the elbow is only like $7 at the parts stores.

 

Oh, didn't notice it was a first gen. Yep, that's a much more common failure point than the throttle body gaskets.

 

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