Vacuum diagram ford taurus 2002

check for vacuum leaks including dash vent control hoses, check fuel pressure, check HO2S sensors

It is on the top of the engine in the fuel supply pipe to the fuel injectors, it has a vacuum hose attached to the top of it.

The age of your vehicle also guarantee's a vacuum leak. It may sound silly but the truth is rubber grommets, and hose's shrink and dry out over time and the harsh environment under the hood makes it worse. Check all vacuum lines and fittings attached to the intake manifold, valve covers (pcv valve), and be sure to check for a vacuum fitting on top of the intake just behind the throttle body. Does it fit tight in the hole? You can seal loose fittings with a high-temp RTV (Red) silicone sealant/adhesive. Several small leaks add up and your engine, heat/AC, and transmission will be all to glad to tell you about it.

Lean on Bank 2 means one side of the engine is getting less fuel or too much air. I also own a 4.0L and I work on these models for this code consistantly. Usually if you have a vacuum leak at the pcv valve hose behind the throttle body you will get a lean Bank 1 and 2.
My recommendation in these cases would be to change the PCV valve (helps with your gas milage) and the fuel filter; other than that you will have to be sure the fuel pressure is correct and there is no vacuum leaks on the driver side of the engine. I am 90 percent sure the fuel filter, pcv valve and clearing the codes will correct this issue.

Here I find one TSB...
MALFUNCTION INDICATOR LAMP (MIL) ILLUMINATED - SYSTEM LEAN DIAGNOSTIC TROUBLE CODES (DTC'S) - SERVICE TIPS

FORD:
2000 Contour
2000-2002 Escort
2000-2003 Escort ZX2
2000-2004 Crown Victoria, Focus, Mustang, Taurus
2002-2004 Thunderbird
2000-2003 Windstar
2000-2004 Econoline, Excursion, Expedition, Explorer, F-Super Duty, Ranger
2001-2004 Escape
2004 Freestar
2000-2004 F-Series

LINCOLN:
2000-2002 Continental
2000-2004 LS, Town Car, Navigator
2002-2003 Blackwood
2003-2004 Aviator

MERCURY:
2000 Mystique
2000-2002 Cougar
2000-2004 Grand Marquis, Sable, Mountaineer
2004 Monterey

ISSUE: This article is intended to aid in diagnosing DTC's P0171, P0174, P1130, P1131, P1150, P1151, P2195, or P2197 (system lean or lack of HEGO switches) when a vacuum leak is present. HEGO sensors, MAF sensors, and PCM replacements are not an effective repair when a vacuum leak is causing the above DTC's.

ACTION: Perform the following inspections/repairs when the above codes are found in memory. Procedure provides instructions on how to make comparisons of the total fuel corrections (using scan tool or equivalent) at idle and high RPM's to help determine if a vacuum leak is the root cause of the DTC's.

SERVICE PROCEDURE:
NOTE FREEZE FRAME AND ADAPTIVE FUEL VALUES (ASSOCIATED WITH "LONGFT" PID) WILL NOT BE AVAILABLE IF A KAM OR OBDII RESET WAS RECENTLY PERFORMED.

NOTE FREEZE FRAME DATA WILL INDICATE THE ENGINE AND AMBIENT CONDITIONS WHEN THE DTC WAS SET. THESE ARE IMPORTANT BECAUSE THE VACUUM LEAKS MAY OCCUR ONLY WITHIN SPECIFIC TEMPERATURE RANGES AND MUST BE DUPLICATED TO DETECT THE LEAK.

NOTE FUEL TRIMS AT IDLE ARE PARTICULARLY SENSITIVE TO VACUUM LEAKS SINCE THE UN-METERED AIR LEAKAGE FLOW IS A HIGHER PERCENTAGE OF TOTAL AIRFLOW AT IDLE THAN AT PART THROTTLE. THE BAROMETRIC PRESSURE (BP) PID IS NOT RECOMMENDED TO VIEW WHEN DIAGNOSING A VACUUM LEAK. BP IS AN INFERRED PID CALCULATED DURING HIGHER ENGINE LOADS.

Tom,
Generally, this is caused by either a vacuum leak somewhere on the top of the engine or dirty fuel injectors. Listen carefully for a vacuum leak [sucking air sound] at or near the top of the engine. Another way to locate a vacuum leak is to spray carburetor cleaner [aerosol can] at small areas, where there are vacuum hoses or intake gaskets. When you find the area of the leak, the carb cleaner will get sucked into the leak. This will generally cause the engine to run better.
Try adding fuel injection cleaner to the gasoline tank. I recommend the Chevron Techron brand of fuel injection cleaner. Advance Auto and Costco carry this brand.

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if you can not find a fuel leak under hood, then check for a bad fuel pressure regulator. if it goes bad it will emit gas fumes under hood. is the check engine light on!! if so it may be the regulator or another leak. also check the evap system, could be a bad or broken hose ( underhood ). check all fuel lines from front to back.

do you have a small propane torch? or a can or throttle body cleaner or anything similar? Spray the propane(Just the gas, do nit light it) or throttle body clean, slowly around the engine and if there is a vacuum leak the rpm will rise when the propane fumes or throttle body spray gets sucked in and you know it will be in that area. Anywhere from the front of the motor to the sides to all the way behind, it might not be a vacuum hose, could be an intake manifold leak. Smelling fuel when shutting off can be a different problem all together.

Unless the car has been operating for a long time without anti freeze there shouldn't be that much rust. The only time a heater core needs to be replaced is, if it is leaking. Look around under the hood for a couple of hoses about an inch in diameter that go from the engine thru the firewall. They may not be side by side. After the engine has warmed up, feel the hoses. They should both be hot. If not look for a valve in one of the hoses. It is operated by vacuum so look for a small hose that may have become dislodged. Also the valve itself may be bad. If both hoses are hot then the blend door isn't working. It also is controlled by vacuum, so look for a broken or dislodged vacuum hose.

You most likely have a big vacuum leak. PCV hose split or a bad Idle Air Control motor (IAC)