Not sure I understand why after installing a cai the 05-08 tend to run "lean"...isn't that controlled by the computer? Sorry if it has already been addressed or if its a stupid question but I don't understand how it can run "lean" if you don't have a fuel/oil carburator mixture.
Why doesnt' the computer adjust to the new intake system? I would think this would be a problem in all vehicles after installing cai therefore leading to a decreased sale in cai or companys addressing such problems. Thanks in advance and don't be too cruel

 

What CAI did you put on. I am having problems with mine also. Do you have stock exhaust?

 

Have no problems yet. I have a 08 fx2 screw 5.4. Just put on a banks cai. Don't have the money to get custom tunes right now. I just don't understand how large companies like K&N and Banks and S&B and all the others have never had issues with this before.
Why won't the computer adjust itself? Isn't that what it is for?

 

Well, I have a 2002, 4.6L and I put on a k&N. their sales staff told me I could use it with stock exhaust. Now, my egr valve is acting up. NOW the sales staff at summit said to put on an exhaust system and it should cure the egr problem, but I will still need to get the tune. So they just want to make the sale!

 

I had already put on a magnaflow exhaust before I installed the banks cai. Not sure about the egr problem. I'm just worried about messing everything up completely. I guess if anything happens I can always go back to the stock intake and take it in and play dumb

 

I would go get it tuned. did you go 3" on your exhaust or 2.5? Im putting exhaust on friday. not sure what im gonna put on still researching.

 

maybe you should research the whole running lean thing first, what trucks are suspect to running lean and why.

 

I thought that is what I was trying to do...Anyone, info?

 

This has been discussed many times so you may not get a lot of replies. Try useing the search button and see what you get. Up above, click on the search tab and then click advanced search. Type in different variations of what you want to know and see what comes up. Troyer did some testing at one time, as I recall.

 

As I understand it, the computer does adjust but it has it's limitations. You have to give it parameters under certain situations, such as max air possible, etc. You have to tell it how much fuel to mix with the different volumes of air. You can't have a program that contains every variable that an engine might face, so you have different settings. This is my simplistic understanding of it. I know I would not run an aftermarket CAI without a custom tune.

 

Yup, Mr.Blue is on the right track.

Your MAF (mass air flow sensor) detects how much air is entering the engine at any given time. The computer uses that info to supply the proper amount of fuel.

Now if you put on a new intake that allows the engine to draw significantly more air, the MAF will 'top out', and you'll run lean.

For example, say the maximum amount of air the stock intake lets in is 2 cubic feet of air per second. So Ford designed the MAF to read from 0 to 3 cubic feet of air per second. Now you put on a new intake and you can pull 3.5 cubic feet of air per second into the engine. The MAF reading is as high as it can go, 3 cubic feet per second, and it sends that data to the computer. The computer puts in the proper amount of fuel for 3 cubic feet of air, even though there's really 3.5 cubic feet of air in the system. Now you've got less fuel than you need and that's when you start to run lean.

Granted I pulled all those numbers from thin air, but I think it illustrates the concept.

- NCSU

 

Great job, NCSU,
The lightbulb just came on for me! nice work explaining that.

Happiness is a greasy/fingerprinted Haynes manual!

 

No problem.

The general consensus was that as long as a new intake is 3.0" in diameter or less, you probably won't have issues with running lean. I say probably, because there have been cases of stock trucks running borderline line lean directly from the factory.

Anything over 3.0" requires a new computer tune to compensate for the additional intake.

- NCSU

 

Very good job of explaining it...thank you. Sorry for starting another tired post but did a search and couldn't find anything to really help...thanks again

 

from what i was told when I bought my Banks for $300 was that I needed a tune, so I went an ordered a gyrphon tuner and tunes just recently, have to wait 4 weeks for the custom tunes before I can install my intake but well worth the wait from what I've been told......definitely something you should always do when you get a CAI is find out if is necessary to get a tune to adjust the computer.....most of the time it is.....


As for me, it only occurs with newer body style mustangs. SN95s(99 to 2004) don't need a tune to run an CAI, not sure why but thats the way it is.