1997 F150 4x4 4.6L V8..LAST YEAR ENGINE LIGHT ON AND RUNNING ROUGH. TOOK TO THE LOCAL FORD DEALER AND $1000 LATER..PLUGS,WIRES,FUEL INJECTORS CLEANED ECT...ABOUT 2 MONTHS AGO BETWEEN 30-45MPH FELT A "SHUDDER" WHEN APPLYING GAS ( EITHER ON HILL OR FLAT ROADS ).BACK TO THE DEALER..$275 LATER..BAD PLUG WIRE AND WATER CAUSING ONE PLUG TO ARC..TRANNY FLUID AND FILTER CHANGED ABOUT 30K AGO.DROVE AWAY AND THE PROBLEM RETURNED..THIS TIME THEY CHECKED THE TORQUE CONVERTER ( NO PROBLEM ) PLUG WIRES AGAIN ( NO PROBLEM ) AND FINALY REPLACED THE FUEL FILTER..THIS TIME THE TRUCK RAN FINE UNTIL ABOUT A WEEK AGO AND NOW THE PROBLEM HAS RETURNED.HELP !!!

 

Have you tried replicating the shudder by placing the truck in drive, w/ your foot on the brake and giving it gas? If its a higher RPM miss you might find it this way.

 

They had a problem with the solenoid that disengages the lock up torque converter. You can buy a repair kit for it and it is an easy fix and removes the shutter. I believe it cost under $100. I cant remember where to get it but I know that is the problem because my friends was doing the same thing and it fixed it.