Nissan Repair: At wits end!!!, vacuum leaks, vacuum gauge

Question
I have a 1996 Nissan Pathfinder SE 4WD. The vehicle idles rough and runs rough regardless of running temperature. It has little power and what power it does have cuts out intermittently. It will stall if left at idle for too long. I am not throwing a CEL although the light does work(verified at ACC position). It is throwing knock sensor and coolant temp sensor codes though(before and even after replacement. Timing belt replaced 8000 miles ago. Complete tune up performed 1000 miles ago(Fuel filter,plugs,wires,oil change,cap, rotor,etc). Fuel pump even replaced. Sea foam ran through fuel system and injected directly into intake manifold. After all is said and done there is no change and 100's of dollars wasted. Also, every time the engine loses power it causes a substantial jerk in what sounds to be the rear universal joint or surrounding area. Please help.

Answer
Hi there, have you check for plugged or restricted exhaust system? With a vacuum gauge connected to an intake manifold vacuum source, rev up the engine and observe the needle. If the needle points steady near or at 0, then the exhaust is restricted or blocked. A muffler shop can check the CAT for collapse or restrictions. Also, check for vacuum leaks, late valve timing, (Vacuum gauge reads between 1 and 10 inch/mercury), opening on wiring  between the ECM and the coolant sensor, (I doubt it could be a problem with the knock sensor). Often, when there is a code indicating that a sensor or actuator had failed, it's a no communication with the ECM for a number of other reasons and not the sensor/actuator fault. The jerking can be checked out later after the the checking and corrections of the symptoms above is done.