94 Ranger Running Rough

warmachine5500 · Sep 7, 2015

94 Ford Ranger 4.0 V6. 120K miles. It's my uncles truck (he's retired) and it hasn't been running well. I replaced the coil, plugs and wires about a year ago. He only drives a few thousand miles a year, and it's mostly around town. The problem sounds kind of like a misfire. I just replaced the number 3 spark plug (passenger side, furthest back) because it was completely fouled with oil and it also looked like there was a piece of ceramic stuck near the electrode. Replacing the plug didn't seem to solve the problem. All the other plugs looked perfectly fine. There's also a clacking sound when the truck is cold, which fades away after about a minute or two of idling. I'll attach videos. I'm wondering if there's a valve or valve seal problem allowing oil to foul the number 3 plug? Or perhaps a clogged catalytic converter fouling out that one plug? And I would think the clacking sound would be constant if there was more severe internal engine damage, rather than fading away. I appreciate any help!

https://www.youtube.com/watch?v=U6quCr44e4o

This is the truck idling after a minute or two after startup. Notice the offending sound has faded completely. Forgive the poor quality videos.

https://www.youtube.com/watch?v=cf-guwt92Kk

This is the truck's exhaust after a few minutes of idling. Notice how it's sputtering.

https://www.youtube.com/watch?v=v5j-VwxWhSc

warmachine5500 · Sep 25, 2015

enjr44 · Sep 25, 2015

My second suggestion is to do a compression test and see what you have. My first is to swap the plug wire from one side of the coil pack to the other and see if the miss follows (waste system).

http://ww2.justanswer.com/uploads/drivefast1971/2010-04-10_180406_3.gif

TpMxRd169 · Oct 6, 2015

I had an after market coil fail on me. 2 month after I put on, a faulty coil could cause rich cylinder, which would explain ur dirty plug, has for the crackling, not idea

warmachine5500 · Oct 8, 2015

enjr44 said:
My second suggestion is to do a compression test and see what you have. My first is to swap the plug wire from one side of the coil pack to the other and see if the miss follows (waste system).

http://ww2.justanswer.com/uploads/drivefast1971/2010-04-10_180406_3.gif

I finally got around to compression testing the engine. The results seem good. They are as follows:

Cyl 1: 183 psi
Cyl 2: 168 psi
Cyl 3: 183 psi (the problem cylinder)
Cyl 4: 180 psi
Cyl 5: 181 psi
Cyl 6: 172 psi

The misfire is constant. I have pulled the plug wires off of the coil pack on each cylinder while the engine is running. They all result in poorer idle, with the exception of the problem cylinder (number 3). Cylinder 3 is getting spark. I hooked up an inline spark tester to confirm that. The only other thing I can come up with is a bad fuel injector on cylinder 3. If that injector is clogged, or it's not getting power for some reason, wouldn't that be the only other thing that could stop cyl 3 from firing? After running the engine a bit and pulling out the number 3 plug, the plug does start to gunk up a little bit, but it does NOT smell like gas.

I'm now concerned that this cylinder has been misfiring due to lack of fuel for quite some time. A while ago, my uncle noticed the truck would develop a shake while in highest gear cruising at about 55-60 mph. That's the only time it would happen. I thought it was a transmission issue, but now I'm thinking this was the problem all along. What are the long term consequences of this? I wonder if this could have caused the clacking I'm hearing on startup? I guess it would be normal for the plug to be all fouled with gunk because there has been no explosion in that cylinder to burn it away.

enjr44 I have not yet tried moving the wires from one side of the coil pack to the other. I don't know if it will make a difference since the inline spark tester showed spark on cylinder 3, but I'll give it a shot the next time I get to play with it. Thanks!

enjr44 · Oct 8, 2015

Well, pull the wire off the coil/plug and run it for a couple/few minutes (you will have two cylinders missing). If the injector is not firing or plugged up the plug will be dry. If wet, spark.

I believe a 94 used batch fire injection so you have a wire of one color going to one side of all injectors and two wires of different colors going to the other side (so three injectors fire together). You know the pcm is grounding the circuit because the other two injectors fire.

Build a jumper wire tester using a #97 bulb (or one of equal wattage). Put it across the #3 injector to see if it is getting power (if it is it will blink or glow very dim). If you have power and a dry plug know what is not working.

94 Ranger Running Rough

warmachine5500

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warmachine5500

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enjr44

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TpMxRd169

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warmachine5500

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