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Old Yesterday | 04:42 PM
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P0171 and 174
My son has 1998 f150. XL model 4.2 auto 4x4. Runs fine. Has CEL. Bank 1 and 2 lean. Sprayed around engine bay with ether while idling and found nothing. Pulled intake hose off air cleaner and blocked with rubber glove. Lit cigar and used small pump to blow smoke in brake booster line. Nothing. Forscan show both banks long term fuel trim at "25", whatever that means. They drop into teens while cruising highway. Opinions on next move?
Fwiw..also have P0133 and P0141.
 
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Old Yesterday | 09:42 PM
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Teens while cruising suggests low fuel pressure. Vacuum leaks usually show up at low air flow, like idle RPM.

Could also be a dirty or bad MAF sensor. What is the MAF sensor reading at idle?
 
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