1999 4.0L OHV Check Engine Light

[RaptorRanger]

Alright, my truck is having a fit. 1999 4x4 4.0L Ranger, check engine light is on and its throwing P0141, P0306, P0303, P0174, P0171 codes. 02 sensor short circuit, cylinder 3, and 6 misfire, lean bank 1, 2... I am thinking its an upper intake manifold leak.

I have replaced:

3 new O2 Sensors (2 upstream, 1 lower after the collector)
new spark plugs and wires
new fuel filter

The mechanic thought the O2 sensors would do the trick. Nope. Going to put in a new upper intake manifold tomorrow and see if that does the trick.

I also heard about a vacuum line near the fire wall on the backside of the motor that apparently is elbow or "T" shaped that is problematic.

Thoughts?

Thanks guys. (and gals)

 

[97RangerXLT]

the O2 sensor short circuit could be a bad wire to one of the O2 sensors and not the sensor themselves. check the connector to make sure it is not grounding out on the body of the sensor or any other area.

AJ

 

[97RangerXLT]

I would get the O2 sensor codes taken care of before digging into the intake. then clear ALL the codes and see what pops up again. after the O2 sensors I would look at the misfire codes. then look at the lean codes and what might be causing them.

Just my thoughts.

AJ

 

[RaptorRanger]

Well, I just took it to the Ford dealer and they did a compression test, Cyl 3 and 6 aren't holding pressure. They are going to check and see if its a head gasket, or a valve seat issue..

 

[riverjig]

Having the same issue. Curious as to what the end result was...