So the last time my truck was in the shop I'm thinking the tech may have fed me a line of BS...

I was on the way to work, and the truck was all but dead. It would start and idle, but it didn't have enough power to get itself moving on flat ground. So here comes Ford Roadside to the rescue! They pulled it up on the rollback and off to the dealership... Prior to that I tried pulling codes from my Edge, and it was clear. So I returned it to stock, and put my Edge in my pocket.

A few hours later they called and said the truck was ready. There was no explaination of what was fixed, so I requested to speak with the tech. He said two codes were present -- bank 1 & 2 lean. He said this was completely caused by my 77-series K&N setup. When asked what he did to fix this issue he stated he reprogrammed the cams because they were all out of wack. He said the K&N flows so well that it was causing the MAF to run at 53% at idle. He said that anything over idle the MAF would be running at 100%.

Although I know its BS that the truck was running lean (as I've had that same setup for over a year without issue) the truck ran GREAT after getting it back.

I have an extensive background in cars, trucks, forced induced and not... Nitrous, 2x4's & 4x4's on 44+ inch tires. This is what I want to know:

When you change intakes on a stock motor, how is said intake going to cause that motor to run lean? Given the intake puts the MAF in the correct location. I don't care if you swap from a filter that only flows 200 cfm to one that flows 20,000 cfm -- the motor is only going to draw as much as needed. I know the inlet to the stock airbox is only ~2.5", and the throttle body is closer to 4". When changing over to an aftermarket intake it makes the entire intake tract ~4". However, the motor is STILL only going to draw as much air as needed.

The only way I can see the K&N hurting/helping perfomance is if the motor is restricted by the inlet size for some reason. If a motor is designed to consume 650 cfm at WOT and stock airbox A will flow 700 cfm I don't understand how putting on aftermarket airbox B that'll flow 900 cfm will cause ANYTHING to change... once again, if the MAF is in the prime spot.

Thanks...

 

Defiitely sounds like a load of bs. If I had to guess the tech probably reflashed the pcm.
The first generation of air intakes did have "lean-out" problems. I would suggest cleaning the maf periodically in case oil from the filter is affecting the maf.
Is your 05 built before June '05 ?

 

'04+ 5.4 3Vs run very, very lean from the factory. Aftermarket intakes could cause lean codes.

 

Okay, I've heard that a hundred times. I'm curious to hear a detailed explaination as to why? Our trucks coming lean from the factory would indicate a tuning issue, not a cold air intake / stock airbox issue.

Just because you give a motor the capacity to suck in more air doesn't mean that it's going to...

BUT as I've previous said: I understand that MAF PLACEMENT is critical.

 

What usually happens is that the aftermarket intake allows unmetered air to bypass the MAF and the O2 sensors pick up the lean condition, and the PCM chokes on a code and pops a CEL.

 

Unmetered air would be a leak post-maf. Because if air passes through the MAF it is obviously metered, but the pcm has set points. (maf-xfer-func) If your engine takes in 5lbm (less restriction&untuned) of air and you only need 4lbm of air (that is 20% more air than you need). The o2s read this 20% more of stoichometery is roughly 17:1 A/F. If memory serves me right it takes 15% lean or 10% rich to throw a CEL based on ford programing.

This is why custom tuning is the best because you can obtain perfect stoichometery everywhere on the RPM band.

 

I just knew you would come along and explain it for us.

 

It is nothing personal to you or anyone.

I just hate to see sheep. Just because one person goes "bahhh" the next person goes "bahhh" thinking they know something but that something is wrong.

 

I might add that all lean conditions do NOT cause a CEL on these motors. We did some pretty extensive research on my truck running it very, very lean intentionally and although it went into the limp mode (lit the wrench) several times, not one of those times did it trip a CEL. Therefore it is very possible and probable that there are quite a few trucks out there running lean without the owner knowing it.....

 

Good point; weaseled, just because it ran good doesnt mean its not running lean.

 

My 04 5.4L had the AF1 installed, and tripped the CEL. I used the Diablo sport to up my fuel curve by increments of 1%. It took 5% to keep the light off. And yes, the truck ran fine the whole time. You can be running lean and never know it. FYI I have the K&N fipk now, and no light ever came on. Not as powerful as the AF1, but DEFINATELY more powerful than the Airaid!