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I have done this. The misfire is isolated to cylinder 3. It doesn’t seem to be ignition related. I suppose the next step is to pull the intake and get a look at the injectors.
The misfire was happening with the old wires and plugs, and since replacing them it hasn’t changed. I think it may be injector related.
Yeah I know what you meant. I’m gonna look into the fuel injector and the plug. I’ll post any results. Thanks a lot guys.
Yes I just thought of that before seeing your post. Perhaps we can try swapping injectors around and seeing what happens.
That sounds like an interesting solution to me.
He tells me there is no spark knock, it runs like a charm before the plug melts. No misfires, no shaking like it’s out of time.. nothing. If it was out of time or running lean there would be other symptoms, correct?
He said he was going to change the fuel filter, but I don’t see how that could effect just one plug. I’ll recommend trying cooler plugs and see what happens. Only other thing I could think would be if the number 2 fuel injector wasn’t putting out the amount of fuel that it should, thus causing a lean condition in that cylinder. Maybe we can try swapping injectors with another cylinder too. Thanks.
If it was running lean, wouldn’t it be happening to more than just the one plug? As far as deposits on the end of the plug – they would have to be building up REALLY quickly. The plug melts within a few hundred miles. I think he checked compression and it was good. None of the plugs, including the one that melts, appear to have deposits.
I’m pretty sure he’s using 87 octane. I’ll tell him to play closer attention for spark knock and see if we can check the timing. Thanks.
I completed the repair a few weeks ago. I thought I’d post the results to keep the forum search function valuable.
The intake manifold gasket was very brittle when I removed it. It was leaking coolant into the oil, and into the cylinder 3 intake runner. I replaced it, the cylinder 3 fuel injector (not sure it needed the injector, but I had one on hand already so I put it in), the thermostat (because why not), and I did an engine flush (motor medic) and changed the oil twice after the repair.
There was coolant in the oil, though I couldn’t see it initially. I left the oil drain plug out while I had the lifter valley open and dumped a few quarts of oil down there to “rinse” out the engine. That’s when I saw the coolant in the drain pain. The coolant in the oil must have been the cause of the clacking sound I had. After the repair, engine flush, and oil change, the clacking sound has disappeared completely, there is no more misfire, and the vehicle is running like a dream. I checked the cyl 3 spark plug after the repair and it was initially very white (probably from burning off all the coolant that was in that cylinder). I changed it and checked it again after a few hundred miles and it looks normal. I have a feeling the catalytic converter might be clogged because it was burning coolant for so long, so I’ll have to get my hands on a gauge and check that sometime soon.
The only odd thing remaining after the repair is the temperature gauge on the dash. The truck never used to run hot, the temp needle would often sit between 1/4 and 1/2 the way up the temp gauge when the truck was warm. Now the needle doesn’t even reach 1/4 of the way up the gauge. It’s just barely in the [normal] range on the gauge. The upper radiator hose is getting plenty hot when the truck is warmed up, so I’m thinking the coolant temperature sensor may be faulty. I did remove it when I took the intake manifold off and cleaned it. I’ll buy a sensor on my next purchase from rockauto and see what replacing it does.
Thanks to everyone for their help and guidance!
I tested the injectors today. I put some carb cleaner in the top and put 12 volts to the leads. I got the good clicking sound and I could see the carb cleaner being sucked into the injectors (no spray from the tip, probably needs higher pressure to do that)
I’m thinking that maybe that intake runner was sucking in so much coolant into the cylinder on every stroke it simply drowned out the fuel/air mixture, so the spark wouldn’t be able to ignite it.
I pulled the fuel rail and the lower intake manifold. You can see coolant in the lower intake manifold in the cylinder 3 port. Most of the gasket came off the lower manifold and onto the top of the motor. The gasket around ALL of the coolant ports looks kinda crappy to me, but the gasket around all of the intake ports themselves looks to be ok.
I also took picture of the bottom of the lower intake manifold. You can see how the bottom of the manifold looks different around the cyl 3 port. It looks as if some of the coolant is stuck to the bottom of the manifold as well. But that’s only around the cyl 3 port. The bottom of the manifold looks normal around all the other ports. So perhaps the lower intake manifold gasket was simply leaking around cyl 3, and the coolant made its way in there?
I’m hoping the lower intake manifold gasket was simply leaking around those coolant ports. I realize I could also have a cracked head or head gasket. It puzzles me as to how this coolant would have gone UP the intake manifold instead of just down into the oil. I’m going to drain the oil to see if there’s any coolant in it. But checking it on the dipstick it appears to be fine. I’m going clean the manifold up really good and check for cracks. It appears to be just a simple manifold gasket failure, but I guess I won’t really know until I put it all back together and see if I’m still using coolant.
I’m also wondering why cyl 3 would have the dead miss. The coolant itself wouldn’t do it right? Maybe that fuel injector was clogged, allowing the coolant to build up in that cylinder. I can’t think of any other explanation.
So I finally got some free time to mess with this Ranger. I pulled the upper intake manifold off and there is coolant in the intake port. I guess that’s what would be causing the misfire and fouling the plug. The upper intake manifold gasket appears to be in good shape. I’m wondering if this means I have a bad head gasket? Or the lower intake manifold gasket is shot? Maybe even a cracked head?
There is no coolant in the oil on the dipstick. There does seem to be excessive water coming out of the exhaust at idle.
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 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?
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.
