Ok guys, any help would be greatly appreciated. I have a 2001 Effy 4.2L. I bought it about 6 or 7 months ago. About 3 months ago I started getting a check engine light for codes 171 and 174, lean banks 1 and 2. I have checked several times for vacuum leaks, replaced the PCV valve, changed the fuel filter(it was nasty), replaced the pcv grommet in the valve cover(it was loose) cleaned the MAF, with aerosol MAF cleaner, checked all my air duct work. I am still gettin these 2 codes every couple of days. My gas mileage has went from gettin 18MPG, even pullin my boat, to 13 or 14 MPG without the boat. Everything I read points toward a vacuum leak but I cannot find one unless it's an internal leak. HELP!!!!!!!

 

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The most common culprit seems to be the throttle body elbow. This little elbow is located on the back of the throttle body and is connected to the PCV on the passenger side valve cover. The elbow in question is notorious for melting at the bend by the heat.

Air induction..do you have a factory set up or a modded setup? Any sort of excessive airflow detected after the MAF will throw the two codes.

Fuel filter, probably not the culprit but worth a check, you can check the PSI a the fuel rail, it should be 30+ psi and 30 is considered low from what I have heard. Its my understanding that the lean code is the result of the fuel system being unable to regulate the air fuel mixture.

There are some smart cats here who will contribute or correct me.

 

I just have the factory air induction system. When I changed the fuel filter, nothing came out. I cut it open and it looked like mud. It sounds like Ford needs to come out with a TSB on this as common as it sounds. When I take my lunch I'll pull it in the shop and check for that elbow, is it on the 4.2? Thanks and I'll let ya know what I find..........

 

I have a plastic line with a rubber sleeve attaching it to the throttle body at one end same deal to the PCV valve on the other end. You can turn the rubber on the line fairly easy but I went ahead and put hose clamps on it to snug it up. I went around everything again with carb cleaner, and someone suggested I try propane, tried that too. I hooked up my scanner and cleared the codes so I guess we'll see what happens...Thanks again

 

I would suggest finding out what you air fuel ratios are and where the fuel trims are at. This may point you in the direction you need to go with regards to the codes. You did insure that the factory induction is closed and tight? The slightest leak in the induction will throw those codes ASAP. Let us know!

 

What's your idle RPM's once warm?

BTW - If you take a brush soaked in mineral spirits and coat the rubber connector before sliding it on - it will shrink the rubber around the fitting for an air tight seal. Beats those bulky clamps that chew into the rubber..

Unless it's a factory clamp..You do the same thing , then you can re-use the factory clamp.

Did you change the elbow back by the firewall (PCV).? You can't see it , but it's where the PCV line ends . That's the elbow that wears out.

 

My PCV only has 3 lines comin off of it. One goes up to the passengers side of the throttle body, one goes to the front of the intake under the throttle body and the other goes to the side of the throttle body or intake I can't remember right now, I haven't looked at one but I guess the 4.6 and 5.4's are different mine is a 4.2 V6... I really appreciate everyones input......

 

It sounds like a plenum/upper intake gasket leak. Try to spray carb cleaner or propane around the gasket when the engine is COLD and see what happens, the gaskets expand when warm and seal up the leak, but will set lean codes. Check the fuel trims while doing this (if they are high in the first place) you'll see them drop fast if there is a leak. This is very common on the 4.2L.

 

Well, I made it 2 days, the evil Check Engine light has returned this morning, I'll have to come up with a scanner to check my fuel trims I have a Cornwell, that is a glorified code reader.

 

4.2L - I'm working on one right now lol - Anyway, clean your MAF sensor if no leaks are obviouse . Reboot - don't erase - reset the KAM instead. You have to do that when you mess with an air metering sensor..

Good Luck..