2001 Sport Trac 4.0 Rough Idle, Code PO174

2L8IWIN

2L8IWIN

Club Member
My buddies 2001 Sport Trac 4.0 V6 is throwing a CEL and the code reads PO174. It has a rough idle and what, to me, sounds like a vacuum leak. I cant locate it though if it does exist. All the hoses look connected and the engine didnt rev after spraying the intake down with starting fluid. People with the same experiences online have pointed to the MAF sensor or PCV hose (checked, and its fine).

any ideas?
 
A code P0174 may mean that one or more of the following has happened:

* The MAF (Mass Air Flow) Sensor is dirty or faulty. Note: The use of "oiled" air filters can cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.
* There could be a vacuum leak downstream of the MAF sensor.
* In the vast majority of cases, simply cleaning the MAF sensor does the trick. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling
* Inspect all vacuum and PCV hoses, replace if necessary
* Check for a dirty fuel filter and proper fuel pressure
 
Is this a OHC motor ? if so it likely has a bad intake manifold gasket, easily repaired and fiarly common.If you have acess to a scanner that can see data streams, spray something hydrocarbon heavy around the base of the manifold and see if the O2 sensors jump way up in voltage for a good bit of time, this will show the vaccum leak plain as day if its there.
 
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