F350 backfires & knocks


I own a 1993 F350. I recently installed a K&N air intake & after a short highway drive, it began to backfire & lose power. I pulled over & let it idle & that took care of the backfiring, but the engine got louder & when I decelerate the engine knocks. What could be wrong?


[b]You may have over-oiled that K&N filter, and the excess oil got pulled into the intake and contaminated the Mass Air Flow sensor. And when this happens the engine runs like crap!

My suggestion? Take that K&N filter and throw it in the garbage! Get MAF sensor safe cleaner, and if you have to, remove the MAF sensor and clean it real good. Reinstall the MAF sensor and a new OEM type air filter.



Thanks for the response. I never oiled the filter, so is there anything else it could be?


[b]If you just installed this system, check for any air leaks. There can’t be any after the MAF sensor. If there is, this can mess up the air/fuel ratio.

But I have to ask. What did you hope to gain by adding one of these aftermarket air intake systems?



Haha. I was hoping to increase fuel efficiency. Any little bit helps with my gas hog. If you can’t tell, I don’t know crap when it comes to engines.


The MAF may be damaged from NOT oiling the K&N filter! Put the original type filter back in, and take voltage and resistance readings on the MAF (Mass Air Flow) sensor with a digital multimeter. The instructions are in the Haynes or Chilton’s manual. The oxygen sensor and/or a faulty engine coolant temperature sensor could be the cause of the poor fuel mileage. ++++ me_art12


A knock on deceleration is the text book indication of a worn rod bearing. What other work was done while installing the air filter system? What brand oil filter is installed? What brand and weight oil?

And, regarding the high performance air filters, they seem like most after market gimick$, disappointing in daily use for most users.

But when properly maintained, the direct replacement K&N air filter has never seemed to be a problem…