I have a K&N 77 series intake and Dynomax 3" cat-back exhaust and muffler installed in my 2001 F150 V8 5.4L Lariat. It all works really well, however, now my service engine soon light is on. What should I be doing? Is this harming my truck in any way?

 

might be running too lean

 

What does that mean? Is there something special I should be doing.

 

First - Double-Check your intake install again to make sure there are no leaks, etc; reset the PCM.

Search for the info on lean conditions - literally hundreds of posts discussing that subject in detail - many of them fairly recent (see/search also the Chips forum) - please don't make me type it all out... again

 

Thanks MGD. there is some great info on those links

 

what you need to do is have the code read... It could be something completely different.

 

Good point built. Coincidence aside, it could be something else entirely.

 

Make sure you plugged in your IAT sensor. I forgot mine and it threw a code almost immediately.

 

also clean your MAF, the K&N oil usually fouls it up.

 

p0401
clean the MAF
check all vacuum lines including theline from the PCV to the back of the throttlebody

Since the light came on, chances are the oil from the filter coated the MAF
You can get a can of MAF cleaner for a few bucks
Use it every oil change