This 2003 Ford Windstar came in with the service engine soon light on. Checking code revealed codes P0171 and P0174, banks 1 and 2 lean. I checked for vacuum leaks and none were found so I moved on to the Mass Air Flow sensor. It is common for them to get dirty and cause these fault codes. The MAF sensor is located inside the air filter housing so it had to be removed. I loosened both hose clamps and pulled the rubber boot from the throttle body and then from the air filter housing. Then I unlocked the spring clamp that holds the two halves together.
The crankcase ventilation tube also had to be removed from the rubber hose and more importantly it has to be put back in place during assembly. You can see it just to the left of the master cylinder.
After unhooking the wiring harness connector I took the housing to the bench for dis assembly. There are several locks that have to be released. I used a common screwdriver blade to pry them inward while pushing the sensor out from the other end.
There is also another wiring subharness that has to be removed. It is kind of a pain but I take my time so as to not cause any damage. Once the two halves were separated I removed the sensor from the housing using and tamper resistant torx bit socket.
This is were the actual sensor elements are located and in most cases you will find a build up or film on the element. I use a pick as shown or a small screw driver and very lightly rub the film off. Sometimes if it is heavy it will lift off in one try but most of the time it takes a little while of very light rubbing to remove the film. Some people use cleaners but I prefer to manually rub it off so as not to cause and damage to the sensitive parts. Many cleaners will damage the plastics.
Just several different pictures of the same sensor. There are two elements inside and the most problematic one is the one further inside that you cannot see.
This is just one of the possible causes. There are many and one of my readers left a link to a repair site that has more answers on this problem.
Ford has a TSB out on this for 1999 to 2003 Windstar. if you want to do it yourself, you need to go to your local parts store or dealership and ask for a “Valve cover repair kit”. This site link gives step by step instructions for the fix.
Understand that I am not looking at the data that your mechanic is seeing that you are in turn relating to me. However it would be unlikely that the O2 sensors or the EGR valve would be causing just those two codes and no others. I always opt on the side of testing to be sure of the problem. Your mechanic has to know what and how to test. You have to be willing to pay for the testing to get the best value in your needed repair.
Hi sparky
I own a 1999 ford windstar that has the same lean codes as above seems like there is so many problems that cause this.
My van keeps getting worse wants to stall during idle so I throw it in park at lights and give it gas also while it does that my battery light flickers on and off but my battery has been tested. My mechanic said three main things o2 sensors,egr valve or gaskets and I am on tight budget what should I do? thanks
A truly lean condition specific to one cylinder can cause a misfire. A true misfire will result in unburnt fuel entering the exhaust and therefore a bank rich condition. So a true misfire will not cause lean codes.
Sparky, I have a 2002 Windstar. I’m getting P0301,P0171, & P0174 codes. Can a fuel problem cause a misfire, or can a misfire cause the lean codes? (chicken or egg problem?) I’m leaning on the spark problem because the misfiring seems to be worse when there’s wet weather. I’ve already changed the plugs and wires; getting ready to change the coil pack, but I realize it could be the 700 codes causing it to misfire(?). Thanks, Jim
Sparky, I did send the car to a dealer (at wife’s insistance after the dirty fuel filter change ruined her favorite sweat shirt). Cost:$99 for diagnostic;$110 for new vacuum hose (main large one that goes under the throttle body);$110 for fuel system flush; this last item I think was a waste of money, right? But the car is running and I am chastened. Forgot $10 for the sweatshirt. I figure about $110/hour and compared to plumbers, dentists and bankers, maybe it wasn’t such a bad deal.