I have a 99 ford ranger with a 3.0L flex-fuel engine. I hear a humming sound above the number 4 fuel injector when I put a screwdriver on the fuel rail and next to my ear. I do not hear it on any of the other 5 injectors when listening to them. I have new spark plugs, and wires. They are all working fine. I have checked for vacuum leaks visually and with a vacuum tester, no leaks. I have a new fuel filter also. The fuel pump sounds normal and is working fine. All of the fuel injectors are clicking equally while the engine is running. Have used a fuel system cleaner also. Checked engine compression with a gauge, everything is normal. Trying to figure out if it might be something in fuel rail stuck after system cleaning or is it a valve in that cylinder making that sound.
You may be hearing the pressure regulator that is relieving the pressure on the rail and returning it to the tank.
SOURCE: engine misfires
You didnt mention having changed the spark plug wires, so that is another item that could be culprit as well. As well, it could be a coil pack that is not working properly.
I cannot recall at the moment if that model year uses coil on plugs or if it uses coil packs. Either way, if it uses a coil on plug set up, take the one for the #3 cylinder and move it to say #4 or anyone of your choice and see if the misfire follows
If it uses coil packs, there is likely one coil pack that controls two cylinders. In that case just swap the coil pack with an adjacent one and see if the problem follows. Pay attention to where the spark plug wires go because it will be an issue if you get them mixed up. You just swap the coil packs around.
I would, however, start with the spark plug wires if you have not changed them already.
SOURCE: rough running, erratic spark
Run a compression test on the cylinders.If reading is low on any drop a little engine oil into the pot. If compression rises you have compession ring problems. Remove all plugs before you try this and place leads away from engine.
SOURCE: 96 ford explorer code p0301 mis fire 1
Sounds like either a bad plug wire, or coil pack. This is about all that would cause the misfire.
SOURCE: 2001 Ford Windstar runs rough.
remove the coil pack and look at bottom of it if it shows any cracks coil is bad very common on these vans if you have a noid light check for injector pulse on #4 if you have pulse and good blue spark most likely the injector is bad you have to remove upper plenum to get injectors out let me know how you make out
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