Engine Misses

NOTE: Engine will miss when cold if one or more glow plugs are not heating.

Fig 1: 7.3L Glow Plug Circuit Wiring Diagram

Courtesy of FORD MOTOR CO.

If engine misses only when cold, go to SYSTEM/COMPONENT TESTS - DIESEL. If engine misses at normal operating temperature, go to next step.
Run engine at RPM which makes miss most pronounced. Momentarily loosen injector line nut on one injector one-half to one turn. Then tighten connection. Check each cylinder in the same manner. If the miss condition is not isolated to a specific cylinder, proceed to ENGINE PERFORMANCE DIAGNOSTICS . If miss is isolated to a specific cylinder(s), go to next step.
Check injection nozzle line(s) for kinks or restrictions. Replace any line that is kinked or restricted. Remove suspect nozzle(s) from engine and test. See INJECTION NOZZLE TESTING . Replace any nozzle that does not pass test. If lines and nozzles are okay, go to next step.
Perform the cylinder compression test. See procedures for MECHANICAL CHECKS in the SPECIFICATIONS - DIESEL article in this section. If cylinder compression is within specifications, refer to ENGINE PERFORMANCE DIAGNOSTICS . If cylinder compression is not within specifications, perform procedures in CRANKCASE PRESSURE TEST in this article. If crankcase pressure is okay, repair or replace valve train as necessary. If crankcase pressure is excessive, overpower cylinder as necessary.