Question about Ford Cars & Trucks
Code P0171 and P0172. truck run rough and stalls. also dies when you come to a stop. it is getting about 4 mpg, whats goin on with this thing?
When I see all these codes i instantly think of two things. Vacuum leak especially intake manifold gaskets and Mass air flow sensors. Spray the engine with carb cleaner when its running and see if you get it to rev up,run rough or run different. Next unplug the MAF and drive the car, see if it runs normal.
Posted on Jun 02, 2009
Have you cleaned the MAFS ( Mass Air Flow Sensor ) which is in the intake by the air filter ( little tower with hole in it ).
Usually the lean conditions are reported due to un-metered air in the system which could be the MAFS not keeping track correctly due to it being dirty.
The other problem could be cracked vacuum lines, usually the one to the back of the throttle body ( under the plastic cover ). This is another way for unmetered air getting into the system.
Start with cleaning the MAFS ( with MAFS safe throttle body cleaner, the can will specifically state MAFS safe, don't assume ), after putting it back together ( making sure the tubing is together from the MAFS to the throttle body ) disconnect the battery for 10 min, reconnect and take for a drive, varying the throttle from 30 MPH up to 48 MPH for 2 cycles, to make sure all the system tests have completed.
If you get the CEL light again, start with checking the vacuum lines ( old enough truck, might need to be replaced ).
Could be other things, but these are the most common ones.
Posted on Jan 11, 2010
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