I have a 97 Ford F350 crew 5 speed manual that has 165000 miles on it about 5 months ago it started to get a vibration that seems to be all motor. It get worse with the RPM's above 2000 and higher. It is not consistent I have had it into a shop twice. Before I took it into the shop the first time it did it I was low on fuel in the back tank and switched it to the front tank while stopped and idling and it was smooth then for a few days. It then did it again with both tanks and plenty of fuel in both tanks so I change the fuel filter and air filter thinking it is starving for fuel or air. I think it is fix nope. It starts vibrating again so I take it in to a shop to get it scanned. The CPS comes up and turbo overspool. We replace the CPS and think we got it. Nope still vibrates or should I say shakes very bad. The shop is on the way so I stop drop me kids off at school and in the little idle time while dropping the kids off it clears up. Run to the shop and scan no codes nothing. Keep thinking maybe the map sensor replace that still does it the only way to make it quit after it starts is to stop shut the truck off for about 10 mins. then its good for a while maybe a few days maybe week. Any suggestions.

 

Wiggle the wires on the ICP sensor, i have had them work loose make a poor connection and run like crap.

Also could be the Under Valve cover harness, they're known for going bad and causing an injector or two to missfire, they can also short out completely and cause 4 entire cylinders to shut off.

Diesel Rod

 

Thanks Ill check all the wire connections and see if anything is loose.

 

Big three-1 Dropped valve-2 flywheel-3 Harmonic balancer.

 

CK valve cover harness ! As stated above . Most parts stores sell a kit to fix it. I have seen many problems with them . The Glow plug ckt melts the vc harness .