I have a 2003 explorer with 139k. I have replaced the plugs, wires, coil, fuel filter, and the #6 injector. The truck still idles rough and it sounds like it has a vacuum leak. All the lines on the top of the motor are tight. Are there any below that I am missing?
Vacuum leak on 2003 Ford Explorer
Pinch off all vacuum hoses with a pliers. If any changes occurs, it could be a leak. One particular area that is comon for these vehicle is the intake manifold gaskets. A propane method is a sure way of detection, but monitoring the O2 sensors is desired when doing so. The manifold gaskets usually are more prone to leak during cold starts.