Continuous intermittent misfire

MISTY LYNN

MEMBER
1999 FORD F-250
5.4L
V8
4WD
AUTOMATIC
221,489 MILES

As you know my truck has a lot of miles on it is last of the heritage series before the super duty line.

The truck has always been taken care of and regularly maintained. However I’ve been having a continuous coil pack/spark plug issue causing it to intermittently misfire while driving.
All of the coil packs and spark plugs have been replaced over the years and it’s only one of them that continuously has a problem. Has anybody found a solution to this is Ford that I can’t seem to find? Any help would be appreciated. This was my father‘s truck and he passed away he went to me and I would like to keep it as long as I can. Fully restored no expense spared.

1 Reply

JACOBANDNICKOLAS

MECHANIC
109,755 POSTS

Hi,

If it is always one specific cylinder, it could be a fuel injector issue, low compression in that cylinder, and how long ago were the plugs replaced and the coil on the affected cylinder?

Here is what I would try: Switch the coil pack from the cylinder that has the misfire with a different cylinder and see if the misfire changes cylinders. If it does, then the coil is the issue. If it doesn't then we need to check engine compression.

Here are the directions for coil replacement. Switch the coil from the cylinder that has the miss to a different one and see if it changes location when scanned. The attached pics correlate with the directions.

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1999 Ford Truck F 250 4WD Pickup V8-5.4L SOHC VIN 3
Ignition Coil-On-Plug (COP)
Vehicle Powertrain Management Ignition System Ignition Coil Service and Repair Procedures Ignition Coil-On-Plug (COP)
IGNITION COIL-ON-PLUG (COP)

Removal

5.4L

1. Remove the primary battery fuse cover on RH side.
2. Disconnect the bulkhead-to-upper intake manifold ground wire.
3. Disconnect the injection control sensor, and the fuel temperature sensor, and position the wiring harness out of the way.

All Vehicles

pic 1

4. Disconnect the coil on plug (COP) electrical connectors.
5. Disconnect the eight fuel injector electrical connectors.

Pic 2

6. Remove the bolts.

Pic 3

7. Remove the coil on plug.

Installation

pic 4

1. Follow the removal procedure in reverse order.

NOTE: Apply Silicone Brake Caliper Grease and Dielectric Compound D7AZ-19A331-A meeting Ford specification ESE-M1C171A or equivalent to the inside of the coil boots.

_____________________________________

Try this and let me know what happens. Also, if you have already done this, let me know.

Take care and God Bless,

Joe

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