I have a 05' F250 5.4L v8 gas Fx4 package w/ 97,000 MI.
When i bought it someone had put a K&N filter system on it that i keep clean regular My check engine light was on and I had to replace all my spark plugs and coil packs 3 of which were seized up. Now my Converters are bad.
Just wondering what people think of the K&N clean and oil filter VS. the one you can clean with soap and water and no oil? Also I am thinking of doing straight pipes and eliminating the converters but don't know what to do about the sensors and the computer. I am looking at getting a chip to program the computer but they are so expensive. I am at the point I cant really afford the converters because they have to be ordered from ford and the chip is not cheap. Oh ya my mileage has gone from about 14 or 15 to about 10 or 11 mpg now it is killin me and I have no power going up hill now.
I hope to get some good ideas anything helps. Thanks!! Also does anyone think the K&N filter could have caused all these problems if so what would you reccomend instead? I was also lookin at the FU chip if anyone has heard of it off of power hungry perf.

 

The most popular gas engine tune on this board is a custom tune from 5 Star.

I use the K&N replacement filter. It works well for me. Some say it doesn't work well but I have run them on multiple gas engines without issues.

AFAIK, there is not a sensor downstream from the catalytic converter, so deleting it should not be a huge issue. Just do it.

You will also want to look at replacing the restrictive Y-Pipe.

 

The biggest problem is people over oiling K&N air filters, this can lead to oil droplets burning on the Mass Air Flow sensor, which leads to carbon build-up. This build-up acts as an insulator on the wire causing the ECU get an inaccurate signal. This, obviously, is going to give poor performance and economy, and could damage the cats and the O2 sensors.

 

The cat's on my 06 F250 5.4L burnt out at 17,000 miles (I bought the truck new in Sept of 06) I was getting abt 5-6 mpg at the time and the truck has Zero power. Lucky warranty took care of the problem, but I think it has returned again... truck just doesnt seem to have the power it did, unless its just this horrible "gasoline" we have now I days... yet again its got 92K on the clock.

I run a K&N CAI on my truck and love it, havent had any problems with it at all... just have to clean it more often than the drop-in filter in the stock box. Doesnt hurt to take your MAF out every once in a while and clean it.

Redford: The 05 and up trucks have a different Y-pipe design than the 1st gen super duty's, the y-pipe is much less restrictive. no need to replace it.

 

I believe that Ford extended the emissions warranty to either 100K or 120K... contact your local dealership for confirmation.

 

Furian: I think its 100K

 

It is sooooo rare for a cat to "go bad" these days. What happened to them?

And do check with dealer. Cats are definitely emissions related items with extended warranty.

Regarding air filters: Premium paper (Napa Gold) is all I will use. I usually keep vehicles for well over 300K miles so need good air filtration.

 

In CA the emission systems have mandatory 10 years warranty. That is main reason why CA models are more expensive.
K&N filters are famous for letting more air and more dust coming through.
When more air is good for the engine, the more dust is not. I heard the "I never had a problem with them" thousands of times, but none of those statement come backed up with oil test showing no dust (silica) in the oil. I do have severe duty OEM filter in my truck and almost 90,000 miles on the element. The vacuum indicator only lately shows some clogging , while several oil test prove perfect filtering.
Additionally the oil AND dust coming from the K&N can and will foul MAF (regardless what salesmen say) what in result will create engine mismanagement, poor performance and dumping raw gas into the cats.
Did I mention that dust create grinding effect on pistons and cylinders?

 

What octane do you have up there? I know when I vacation in Colorado, the Regular Unleaded there is 85 octane, which is too low for newer vehicles. Maybe the octane is too low for the Regular Unleaded where you are?

 

Catalytic converters do go bad, causing excessive back pressure and a huge loss of performance.

You may want to double check the emissions warranty. Vehicles over 8500 pound GVWR are not governed by the same laws as passenger cars. I think the emission control warranty is only 50,000 miles for us.