Mike Poore
04-13-2008, 04:38 AM
The 2002 F-150 4X4, 4.6L, 5sp, 100,000 + miles needing it's first tune-up, was missing and bucking under load, and getting worse. After changing out the plugs the strangeness went away ...let me explain.
The door locks would cycle to open, even when not locked, only when the engine was running, at weird intervals, sometimes 5 or more times in a few seconds. Most times it would happen while driving, and never when the ignition switch was off. We could push the "lock" button, and, snick, back up they'd come, and keep cycling, while driving, and in retrospect, under load. The key fob thingeys worked just fine, and I switched to the spare set, making no difference.
I had the door panels off, looking for a short, and disconnected the switches, without success. After changing the spark plugs, the problem went away, and has not returned.
The solution; and by now, some may have guessed, must have been the engine miss-firing. It could be there's a wire that got disturbed during the plug swap, but it's more likely, due to the high current/voltages caused by one or more of the coils backfiring when there were electrical transients/signals being generated, at the correct frequencies, causing the door locks to cycle.
Strange as it seems, I believe this to be the solution. It may be applicable to weird electrical malfunctions with all sorts of stuff in our vehicles.
So, when your radio starts doing unusual things, or the gages or warning lights, or heater ... anything with electronic sensors goes wacky; you may want to go looking for a bad coil pack, or spark plug.
Or ...it may have been the black helicopters up here at site "R". :hide:
The door locks would cycle to open, even when not locked, only when the engine was running, at weird intervals, sometimes 5 or more times in a few seconds. Most times it would happen while driving, and never when the ignition switch was off. We could push the "lock" button, and, snick, back up they'd come, and keep cycling, while driving, and in retrospect, under load. The key fob thingeys worked just fine, and I switched to the spare set, making no difference.
I had the door panels off, looking for a short, and disconnected the switches, without success. After changing the spark plugs, the problem went away, and has not returned.
The solution; and by now, some may have guessed, must have been the engine miss-firing. It could be there's a wire that got disturbed during the plug swap, but it's more likely, due to the high current/voltages caused by one or more of the coils backfiring when there were electrical transients/signals being generated, at the correct frequencies, causing the door locks to cycle.
Strange as it seems, I believe this to be the solution. It may be applicable to weird electrical malfunctions with all sorts of stuff in our vehicles.
So, when your radio starts doing unusual things, or the gages or warning lights, or heater ... anything with electronic sensors goes wacky; you may want to go looking for a bad coil pack, or spark plug.
Or ...it may have been the black helicopters up here at site "R". :hide: