Hey guys.
A few days ago my "check engine" light came on. I didn't get a chance to take my truck in right away and everything sounded and felt the same so I wasn't too concerned. Yesterday I stopped by a shop and the guy plugged up a computer to the port under my steering wheel and a couple of codes popped up. The text on both said "too lean" and the guy told me it appeared to be an airflow problem. He mentioned it could be the Master Airflow something-or-other. He looked under the hood and said he didn't see anything on visual inspection but could turn the check engine light off and if the problem happens again, the light would come back on again. Cool! Works for me! - and he didn't charge me anything, so even better.
So, I left the shop, drove the hour home, no problems.
This morning, left home, drove about an hour and 15 minutes when the light came back on.

My Ranger is a 2001 XLT, V6, 4.0L with 105,000 miles on it.

Any ideas what could be going on here? Is this common?
Now that my extended warranty is kaput, I really can't afford any expensive repairs so I'm hoping this is something I can take care of myself.

Ideas very much appreciated.

 

Do you recall the actual code numbers?

Running lean usually means that unmetered air and/or not enough fuel is getting into the cylinders (or a combination of both). Any air that gets into the system AFTER the Mass Air Flow Sensor (MAF) is considered "unmetered" air. Start by checking all vacuum hoses and connections, this is where a lot of these air leaks can be found.

Also, try cleaning your Mass Air Flow Sensor (MAF). A dirty MAF can cause lean codes, as well.:

https://www.ford-trucks.com/forums/s...hreadid=126093

Keep us posted.

 

Unfortunately, I didn't write down the codes and don't remember them.
Thanks for the info - I'll take a look at all the airhoses and try cleaning the MAF. Will removing the battery cable for 15-20 minutes also clear out my check engine light?

 

That will clear the codes and light until the fault is detected again.

 

Okay, just cleaned it up today.
It didn't *look* dirty but I guess looks aren't everything.
I'll drive it a couple hours tomorrow and see what happens.

 

So far, so good. Made it to work today in under an hour (which is very unusual - you folks in Metro Atlanta know what I'm talking about).
The Check Engine light stayed off for the duration of the trip but it didn't come on last time 'til about 1 hour 15 minutes so I still have some driving to do to really test it out.
Thanks for the info.

 

Well, the light came on again on the way home last night.
I'll see if I can stop by the auto shop again this evening on the way home and get the guy to hook up the gadget so I can write down the codes.
Otherwise, should the IAC be next in my cleaning adventures?
The air filter looks clean enough but maybe I should go ahead and replace that, too.

 

Don't replace anything until you get the codes.

 

Okay - got the codes.
P0171
P0174
The guy at the shop told me it could be Mass Air Flow or possibly a vacuum leak.

 

Well, I see it has 105K miles on it, so maybe we should begin with some basic questions.

When you cleaned the MAF sensor, did you take a look at the air filter, if so how did it look???? How many miles since it was last changed????

 

I agree with the shop, try cleaning the MAF and checking for vacuum & exhaust leaks.

 

I had a similar problem with my 4.6. It was hard to diagnose because the check engine light wouldnt always come back on at expected times. It seems the reason was, I would drive normally and then I would hit the gas hard,entering highway etc. A short while later CEL would come on.It seems that the fuel filter was plugged and when I asked for alot of fuel, it wasnt there, therefore the running lean problem. When was the last time you changed your fuel filter? Worth a thought

 

I changed the air filter @ 98,000 miles so about 6-7,000 miles ago. I did take it out and examine it. It looks clean. Most of it is as white as the day I installed it.

Canuckeh - I've never replaced the fuel filter. I'm probably due regardless.

So, anyone with a shop manual - what exactly do those codes mean, anyway?

 

Ok pawpaw missed your previous statement that you had already checked your air filter when you cleaned the MAF sensor & it hasn't been that long since you installed the present one, so it need not be changed again.

If the fuel filter hasn't been changed in all these miles, it will need it.

It can get plugged enough to cause restricted fuel flow, such that the system can't compensate for it & the air/fuel mixture can go lean, as the two codes you have 171 & 174 are lean mixture codes, System adaptive fuel too lean bank 1 & bank 2.

It means both cylinder banks are running lean on fuel.

Canuckeh says he has had a similar problem, under similar driving conditions, that was fixed with a filter change.

It may or may not be the filter, but at 100K+ miles it's long past needing to be changed, so I think you have the right idea to do so.

They are not difficult nor expensive to replace & your fuel pump will love you for it.

If your not having idle problems, I don't think I'd mess with the IAC.

I'd check the vacuum lines as Ken00 suggesed & maybe the intake manafold bolts for proper torque. The 4.0L has a history of intake manafold gasket leaks.

So do the fuel filter change & look under hood for the obvious & keep us posted on how it goes.

 

Thanks for the detail - that helps a lot.
As for the IAC - I don't know that I have an idling problem per se, but when I crank it up first thing in the morning, it revs up and then revs down just to the point where I think the engine may cut off but then it revs back up and starts to idle.
The idle is a little rough but I've been attributing that the engine idle dampers, which I've never replaced.
Allrighty then. I'll replace the fuel filter and go from there.