ok I will make it simple. The computer has a set of paramaters it can work in. They are already lean from the factory. This lean condition will not cause a problem for most ppl. I run my truck hard so its in the 5k+ rpm range ALOT. So I had to tune mine. If your pulling alot you should tune it. The intake will make it leaner. it may not make it lean enough to trip the CEL, but it will make it run leaner. Mine went .5 leaner so it was 13.6 instead of 13.1. thats not bad, but if the truck were stock it would have put me at 15.7 becuase it was 15.2 stock. Again they are not my truck, so if ya run them and are happy good for you. If you want to treat the engine right get a tuner with the CAI.

 

very well put. that is kind of what i was leaning towards in my scenario up above but just didnt quite have the right words... after talking with a few mechanics here they all back up what you said about most f150 running a little leaner than most vehicle.

 

I know this thread is sorta "old".
But I have to wonder how the hell you are running lean with just a CAI. Only way I see it running lean is if you have a leak AFTER the MAF sensor. This is because you are introducing unmetered air into the engine and the maf cant pick it up to compensate. Leaks or more air before the MAF will NOT cause it to run lean. Because that air is being metered.

 

I am with you on this. From my experience, the air is metered after at the MAF.
Due to physical design, the MAF will only allow X amount of air through it and its design shapes the airflow no matter how big the filter is or if there is a filter at all.
The MAF tells the computer how much air is comming through the MAF.
The only other variable is the the air intake temp sensor. That tells the computer the temp of the incomming air.

 

I performed the mod last weekend and it works as advertised. Inexpensive, simple and only one hour. Looks professional and the difference in performance is noticeable. Appears a gain of 2mpg. With nitrogen in the tires (also a must for the $20 spent) I am getting better performance, smoother ride and 4mpg to the better. Good suggestion and would encourage this mod as a good,inexpensive positive results undertaking. With the K&N and free flow exhaust the 4.6 runs fantastic!

 

Not to resurrect a couple month old thread again.... but here goes.

The reason it can still run lean is due to the factory trim tables. It has a preset table telling how much fuel it should be putting in. The computer uses an adaptive strategy table that allows it to make only MINOR adjustments to the fuel trims. When you put something on that leans it out by 5% you are beginning to exceed its capability to adjust. This will cause your truck to run leaner. Remember, the computer only can adjust within it's defined ranges. If it needs to adjust further it will assume it's because something is broken and it will trip a CEL then go into a limp-mode designed to continue safe operation until you can get it to the dealer.

Also remember that our o2 sensors are not wideband o2s... they are narrow band. They are designed to work in a very finite range. As you change things above that leans out your output you are now working in a different part of the narrow range on your o2 sensors. This is just one of the many difficulties your adaptive computer is trying to cope with.


For example, (and these numbers are only to make the math easy) let's say your o2s have a range of +-2 AF. If you run an even 12 your o2 can read anything between 10-14. Now... if you install a CAI and are running leaner your computer will try to adjust things however it won't be able to fully compensate due to the limitations on how far it can adjust fuel trims. Now you are running at 13 AF. Now you have a new range of +1 to -3. If you quickly step on the throttle the car will pull in more air but lags behind in adding the fuel (since it uses the data from the factory fuel trim specs until the o2 lets it know there is a problem... which there is always a slight delay before this happens). So for a brief moment you run even leaner than your 13. Let's say this puts you at 14.5. Remember than narrow range on your o2? It's just been exceeded... so your o2 is still sending voltage readings that indicate 14.0 but you are really at 14.5. This means the computer won't adjust back quickly enough and you are running lean longer than necessary.

Is this a big problem? That's up to you... but with this being my new truck and my baby I think I'll wait until I can get a tune.

 

Are there any drawbacks to this? Lost mileage, computer problems, etc?

 

The threads all over every f150 forum cover the drawbacks in full detail... however a short list is:

Pros:
Better throttle response, better mpg (only for some people), more power
Cons:
Runs Lean (wears out your o2 sensors, your cats, increases combustion temp).


Running lean can cause very serious long-term damage to an engine... Read about the mod a bit more. A lot of people end up saying its okay on the 03- but the 04+ is a bad idea. Dunno... it's up to you. Just do a bit of research before you make up your mind.

 

I literally laughed out loud at that