Our 03 4.0 V6 Mountaineer with 21K miles has a rough idle. You can feel the engine at idle in park vibrate the vehichle. Also, when you pop the hood the engine visably shakes , and rmp varies.


This vehichle recently stalled several times waiting for traffic lights to change. Also, MPG reading has dropped from 20.6 HWY , to 16.9.


We really like the vehichle but these issues along with hard shifting have us second guessing our choice.

On the older 4.0 v-6 i know they had intake manifold gasket concerns also sounds like there could be a vacuum leak somewhere. As long as it is under warranty get it to a dealer im sure they will be happy to help..

We did take our mountaineer to the dealer today for the hard shifting , and the rough idle. After the vehicle was test driven DIA checked SOLINOID CHECKED , PIDS OK , OASIS found PCM needed updated. They re programmed PCM , Vehichle shifts OK.


Rough Idle again checked PIDs / Data/ IAC valve all OK. Re programed PCM for both issues Idle , and shifting. What does the PCM stand for ? Are there 2 of them ? How do you know when they need re programmed ?


At this point th evehichle runs great , shifting well , and does have a smoother idle.

The PCM is the power train control module basically the brains of the car. There is onlyone PCM so the programming fixed both concerns.Occasionally over time the current programing will not work with the vehicle as it is driven and need to be updated due to as things wear and sensors begin to get dirty the program tries to run everything as it is new.its basically a new program for the vehicle to run on.. There is really no way to tell if it needs to be updated and it is not updated with a new program often it just happens sometimes. Glad to hear all is well now though