need a serious tech on this one

[snooper0069]

my 1993 4.0 explorer runs rough at idle . all 6 spark plugs run white . compression is 160 on all 6 cylinders. no vacuum leaks on engine . fuel pressure is 45 pounds .
every sensor is new on this truck . the only things not changed are the fuel injectors and the p.c.m.
iv thought about the sensors and decided that if one or two where partially clogged ,all 6 would not be running white (lean). i guess the only thing left would be to change the darn p.c.m.
by the way iv checked for vaccum leaks - none

any other suggestions short of dowsing this truck with gasoline would be appreciated, this is getting very expensive to diagnose . iv tried the ford dealer and those idiots are saying the rough idle is norm .
well iv listened to other 1992 and 93 models that purr like a kitten .

 

[SWLathrop]

White/chalky deposits are normally due to overheating. To cure this you must first verify that the plug is the correct heat range, the ignition timing settings are correct, the air/fuel mixture is not too lean, there are no vacuum leaks and that the EGR valve (if equipped) is functioning properly. The best way to check for a vacuum leak is to remove the hose from the throttle body. Then while the engine is running, cup your hands over the intake and slowly cover up the air intake. If you have a leak, the engine will start to smooth out as the leak will compensate for the air being blocked off.

 

[snooper0069]

thats all been done by myself and other mechanics . no vacuum leak exist . the timing has been checked and is 10 degrees top dead center . , the advance works also.

 

[410Fortune]

Are you SURE your lower intake gasket and bolts are not loose?