1996 Ford F-150 bank one to lean

You have too much air, not enough gas, two possibles are vacuum leak, and fuel pump, if it has the plastic manifold, do this. You may have a vacuum leak, get a can of spray gumout, spray the vac lines and maniflod area, when the idle changes, youve found the leak! You want the engine running and spray on the outside but do direct the stream onto the hoses, if it is a vacuum leak, the engine idle will change speed, then you have detected a leak, repair the vacuum leak and see how it runs!
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