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Ray M.
Ray M., Ford Master Tech
Category: Ford
Satisfied Customers: 3009
Experience:  30+ years in trade, Ford Master Tech, Journeyman Automotive Tech
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2002 F350, 7.3L powerstroke. Fuel Economy has dropped 20-25%

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2002 F350, 7.3L powerstroke. Fuel Economy has dropped 20-25% in the last year. Wheel Alignment has been done. Had truck in dealer for a look over. They found and replaced leaking intercooler boots. After that repair, exhaust "Y" into turbo started leaking, but milage was back to normal. Repaired exhaust "Y" and mileage fell again. Could there be a fuel leak or something else happening? There is no evidence of a fuel leak? Would they have pulled codes when doing the look over, or do I have to specifcally request it? Mileage drop is not due to ULSD fuel, as I ran ULSD fuel for almost a year before this milage drop occured. Truck runs smooth, and has no power issues.
Submitted: 7 years ago.
Category: Ford
Expert:  Ray M. replied 7 years ago.

Have it scanned for codes and have the EBP monitored(exhaust back pressure).Since you claim that the mileage increased when the exhaust was leaking,it would lead me to believe the catalytic convertor may be getting plugged,this will show up as increased backpressure and poor mileage.

Customer: replied 7 years ago.
Is not the muffler the largest restiction in the exhaust system? What do the insides of the CAT look like, I didn't realize it could plug. The truck has 140,000 miles, is plugging of the CAT common?
Expert:  Ray M. replied 7 years ago.
Yes the cat convertor is a common problem on the diesel,mostly plugging due to poor fuel quality producing excess soot. If you can picture very small honey comb looking material with the holes about 4/32 in diameter,that is what the convertor looks like inside.
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