Well, the infamous Check Engine Light popped on so I ran the codes. It was throwing the P0171 and P0174 code. So, according to the Haynes manual and the code book that came with the handheld reader it was saying that my "System was too Lean" What in the world does that mean? Is that why Im getting poor gas mileage, and more importantly what do I need to do to fix this?

Thanks guys

 

it means that your engine is not getting enough fuel, or your computer thinks that it's not getting enough fuel.

looking at your sig, one thing i can see that could possibly attribute to that is the K&N.

if you are in fact running lean it could be the cause of your poor milage. but the only way that will happen is if you have a misfire AND the PCM is trying to compensate.

when you run lean you're acting getting less fuel and more air. what that means is that the fuel that IS making it into the cylinder will be burnt off better, hotter, and cleaner than a normal mixture. BUT!!! this means the heat and pressure inside the cylinder wall is greater and will severely decrease engine life. Also, the lubrication is degraded and can cause scoring, and pitting on the cylinder walls.

as far as a fix goes, well my knowledge doesn't run that deep on these engines, so maybe someone will chime in...and keep in mind, what i listed above is a worst case kinda thing...there are alot of sensors that can crap out that can cause this code..

just my .02

 

Here are a few common problems:

"unmetered air" leak between the MAF and the throttle body;
leak in the PCV system, especially the hose elbow;
leaking intake manifold gaskets;
any other vacuum leak.


Less likely but possible:

Low fuel pump pressure/clogged fuel filter/dirty injectors;
"lazy" oxygen sensors (the front ones).

 

Vacuum leak most likely.

Although.. once upon a time I did get a 171 code from a piece of debris that got stuck to my MAF wire. A little contact cleaner sprayed on there and it was fine. (after clearing the code)

Rich

 

Thanks guys for the repsonse.

So, I should first look at the MAF and try cleaning that? Where might this vacuum leak be that you speak of?

 

It is most likely the lower to upper intake manifold gaskets.They are rubber and they dry out and crack over time.Mine did the same thing.I replaced the gaskets and it fixed it.This is a very comon problem to the 4.0 OHV.

 

Wow, Marc, you're still around!

Good to see you posting.

 

Awesome, where will the lower and upper intake gaskets be located on the 4.0 OHV. Sorry, but im still a noob at all this engine stuff....but im definately learning!

 

https://www.ranger-forums.com/forum2...ad.php?t=27084


Read here. I just did it yesterday. Took only around 2 hours. Glad I did it, solved my problems.

 

Another source for your reading pleasure:

Replacing Upper Engine Gaskets on the Ford 4.0L OHV