1991 Ford E-150 Problems

The engine may have a misfire, hesitation, and/or run roughly – notably after a service and/or ignition wire replacement. If after recent ignition wire replacement, the cause can be misrouted ignition wires. The wires from the distributor to the valve cover must be routed correctly to avoid interference and induction crossfire. Verify all clips are used to secure and separate ignition wires.

Common sources of rear axle leaks are the rear differential cover seal, and / or the pinion seal. Reseal the rear differential cover with the appropriate sealant and / or replace pinion seal for leakage.

Transmission fluid leaking from the front of the transmission bell housing may also be accompanied with shifting and transmission engagement issues. This is often caused by transmission overheating and is the sign of a significant internal transmission problem. The superficial cause is the failure of the front pump seal of the transmission. The immediate repair is to remove the transmission, replace the front pump and seal, replace all fluid with the transmission filter, and verify proper flow through the transmission fluid lines and cooler. It is also recommended to make sure the vehicle is not pulling a load that is heavier than the gross vehicle weight limits because this can cause the transmission to overheat. Depending on the transmission's mileage, this can also be a good time to consider a complete overhaul or replacement with a remanufactured unit, as often just the pump and seal replacement is a short lived remedy. This concern relates specifically to the E4OD and 4R100 automatic transmissions.

This concern relates to vehicles equipped with the E4OD and 4R100 automatic transmissions. Fluid leaks from the rear of the transmission and excessive vibration felt in the vehicle while driving can be caused by a lack of lubrication to the rear of the transmission and rear seal failure. The extension housing (rear portion of transmission) can lose lubrication if the fluid supply hole becomes clogged. This leads to rear seal failure from lack of lubrication, and can cause bearing failure in the extension housing. The extension housing and gasket should be replaced and verify the fluid supply hole is clear of debris.

The front end may make a rattle noise over bumps. There may be handling issues, and play in the front wheels on inspection. If there is up and down movement on the front wheels while the lower control arms are being supported, inspect the upper and lower ball joints for excessive play. These are prone to failure from moisture entry and lack of lubrication. The ball joints should be replaced as needed.

Electrolysis can cause repeated failures of the heater core and radiator. The diagnosing technician should check for voltage present in the coolant, with the battery disconnected, because electrical current in the coolant causes electrolysis. Corroded or deteriorated parts should be replaced, and the coolant should be flushed. Ground straps can be added to help prevent future corrosion of components.

This concern is relating to the AOD automatic transmission typically seen mated with the 4.9L 6 cylinder and 5.0L V8 engines. If the Throttle Valve Cable (TV cable) becomes detached from the throttle valve, transmission shifts can be hard or delayed. The grommet that secures the TV cable to the throttle should be replaced. Our technicians note that delaying repair of this concern can lead to internal transmission damage due to the abnormally high internal pressures present when the cable is detached.

In some cases with higher mileages, the Check Engine Light may come on due to insufficient Exhaust Gas Recirculation system (EGR) flow. For EGR flow concerns, the EGR valve is usually recommended for replacement and the intake manifold is removed to clean the EGR passages in the engine, which have clogged with carbon over time.

On vehicles equipped with the E4OD (4-speed automatic) transmission, harsh engagement of the automatic transmission when shifting into reverse or drive, and irregular shifting while driving can be caused by failure of the Manual Lever Position (MLP) sensor. Water intrusion can lead to failure of the sensor, which should be replaced with a revised sensor and wiring kit to prevent future failure.

A defective thick film ignition (TFI) module can cause the engine to stall while driving, or the engine may not start. A failed TFI module will require replacement.

Sludge build up on the throttle plate and/or idle air control valve can cause a poor engine idle, stalling, and/or hesitation – especially when the engine is still cold. The correction is to install a new idle air control valve spacer kit to prevent the sludge build up.