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94 Ford Ranger 4.0 V6 automatic. 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 6 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. I pulled the number 2 plug and it 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 6 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!
This video is the truck during a cold startup. The clacking fades away after a minute or two of idle.
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This is the truck idling after a minute or two after startup. Notice the offending sound has faded completely. Forgive the poor quality videos.
youtube.com/watch?v=cf-guwt92Kk
This is the truck’s exhaust after a few minutes of idling. Notice how it’s sputtering.
youtube.com/watch?v=v5j-VwxWhSc
Unfortunately, I don’t see any easy way out with this one.
The noise frequency seems fast enough to be valve-train related, but also could be an exhaust leak. The wet #6 plug suggests to me that you have some worn valve guides on that cylinder.
If she were mine, the first thing I would do would be to remove the valve covers and make sure nothing is loose in the valve-train. Also check for broken valve springs. You may want to turn the engine over by hand while you perform your inspection just so you don’t miss anything.
Remove and inspect your plugs, and perform a compression test.
I would also inspect the exhaust manifold for cracks and blown gaskets/donuts.
Once you have performed the above, then you should have enough information to proceed to a repair solution. Good luck and keep us informed.
I would check to see if you even have a spark at #6 cylinder. Oil leak aside, a plug with a good spark has a certain amount of self-cleaning ability. If the plug was heavily fouled, it could indicate no ignition in that cylinder.
The old fouled plug had a piece of porcelain broken off. The broken piece was jammed near the electrode. I’ll post pics soon. I’ve got a compression tester and a spark tester on the way. Will post updates as soon as I can. I’ll also pull the new #6 plug and all the other plugs to check their condition.
Broken porcelain can point to several different things.
It might as simple as the plug having been mishandled, dropped and damaged during installation. It could be the result of the plug being gapped in a ham-fisted manner. (The old-school plug gapping pliers could easily damage center electrodes and ceramic insulators when used carelessly.)
As for engine-related causes, make sure it’s the correct plug for the engine. I’ve seen a few cases where people mistakenly installed plugs that were too long, or were missing the crush washer on the plug seat, and piston contact damaged the plugs.
Detonation in that cylinder could be a likely cuprit too. It sounds like that cylinder has an oil control problem, which could lead to pre-ignition, and pre-ignition often leads to detonation.
Given the plug was oil fouled with debris, I would start by looking at mechanical as many have suggested. If you have a mechanical issue with the engine you need to address that first. More info here.
http://www.ericthecarguy.com/faq/solving-automotive-performance-issues
Good luck and keep us posted.
The noise is more than likely related to worn hydraulic lifters, but this engine is also known for poor oil delivery to the upper pushrod ends and the rocker arms. It might be possible that your pushrods and/or rockers are getting to the point where they need replacing.
Might be a stretch, but I wonder if the broken porcelain changed the heat range enough for the plug to foul.
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 (cyl 3 is the one with the fouled plug, not cyl 6 as I previously stated. My bad)
Cyl 4: 180 psi
Cyl 5: 181 psi
Cyl 6: 172 psiThe 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?
Yes, based on your diagnostic tests so far, I would have to say it’s the fuel injector on #3. To confirm this even more, you can swap the #3 injector into a good cylinder and see if the problem travels with the injector.
However, the clacking sound may turn out to be a separate issue.
To access the injectors, I think I have to take off the upper intake manifold. If that’s the case I may just throw the $40 at a new injector and see what happens.
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? Could this 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.
I’m not familiar with the 4.0 V6, but the injectors should be located on the intake runners where they mate with the heads. You might have to move some stuff to get at them, but they should be out in the open.
There are no real consequences with an engine that’s been missing for a while (except for the fouled plug), as your compression test shows. As for the noise, I would check the exhaust system from the heads back. As an aside, some older Chevys had a heat-riser valve installed just after one of the exhaust manifolds. I have seen these contraptions fail and make a loud, intermittent noise similar to what you have in the video. I don’t know if the later Fords had a similar setup, but I would check to be sure. It also sounds like it could be a bad lifter. You might try hot lashing the valves (if rockers are adjustable) and see if this affects the noise at all (better, same, or worse).
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