Cylinder-1 Misfire: advice needed

[Salonika]

My question: can I disconnect one fuel injector to help reduce vibration from a cylinder-1 misfire? I can’t think of any negative consequences from doing this.

I’m on a road trip and dealing with a rough running engine, codes thrown only for cylinder-1 misfire. I’m making it work by running higher RPM’s whenever possible, seems to be ok that way. Been the same for over 500 miles now, everything else is normal. Any advice or opinions welcomed.

 

[Justice R]

I doubt that disconnecting the injector will reduce vibration. It will probably make it worse, as you’ll probably be making an intermittent misfire into a permanent one. I can’t remember which side the #1 is, but if you can access it pull the plug and clean it. Common cause for misfire is oil leakage around the spark plug tube seals on the valve covers allowing oil to pool around the plug causing spark to ground out on the head rather than jumping the gap on the plug. Also check the easy stuff make sure plug wires are pushed all the way into the coil packs on top of the plenum.

 

[nwoods]

By disconnect, just undo the wiring harness. Do not remove the injector itself, unless you are swapping injectors to a different cylinder bank to determine if the misfire is due to an injector, coil pack, or spark plug

 

[Salonika]

I doubt that disconnecting the injector will reduce vibration. It will probably make it worse, as you’ll probably be making an intermittent misfire into a permanent one. I can’t remember which side the #1 is, but if you can access it pull the plug and clean it. Common cause for misfire is oil leakage around the spark plug tube seals on the valve covers allowing oil to pool around the plug causing spark to ground out on the head rather than jumping the gap on the plug. Also check the easy stuff make sure plug wires are pushed all the way into the coil packs on top of the plenum.

If the injector electrical is disconnected, no fuel would enter the cylinder so there could not be a misfire, the cylinder would simply be dead……I’m not sure how much the vibration difference would be in terms of the overall engine balance but can it really be worse than my current situation with an explosion happening at the wrong time??

 

[MontySquareo]

a misfire is when the cylinder fails to ignite the fuel in it, or when there's no fuel to burn. cylinder number 1 is the front cylinder on the passenger side, and on the 3rd gen Montero it's the only cylinder that you can remove the spark plug without taking the intake off. i would unplug the injector, and if you can easily remove the spark plug i would check for spark at the plug. if the injector is firing but the fuel isn't getting burned your cat may be glowing hot from the extra fuel. also you can listen to the cylinder 1 injector with a screwdriver and if it's not ticking the injector is probably stuck or not connected electrically.

 

[Salonika]

a misfire is when the cylinder fails to ignite the fuel in it, or when there's no fuel to burn. cylinder number 1 is the front cylinder on the passenger side, and on the 3rd gen Montero it's the only cylinder that you can remove the spark plug without taking the intake off. i would unplug the injector, and if you can easily remove the spark plug i would check for spark at the plug. if the injector is firing but the fuel isn't getting burned your cat may be glowing hot from the extra fuel. also you can listen to the cylinder 1 injector with a screwdriver and if it's not ticking the injector is probably stuck or not connected electrically.

I wouldn’t call it a misfire if there is no fire…….a misfire creates an unbalanced firing sequence and can be felt and heard usually. I’m wondering how bad of a vibration would be induced by stopping ignition completely. Is that going to be worse than continuing with a misfire?

 

[MontySquareo]

you may not call it a misfire, but when a cylinder doesn't fire it will set misfire codes and most people would define that as a misfire. unplugging an injector for a misfiring cylinder shouldn't change how the engine runs.

 

[Inyo_man]

Did you try swapping the coil pack or wire yet?

Cheers

 

[Salonika]

Did you try swapping the coil pack or wire yet?

Cheers

I’m on the road and I’m still moving where and when I want to, just running rough. I’ll do this when I get home, hopefully, in 600 miles.

 

[Justice R]

It doesn’t matter what you choose to call it, the definition of misfire is when a cyl fails to fire.

If the injector electrical is disconnected, no fuel would enter the cylinder so there could not be a misfire, the cylinder would simply be dead……I’m not sure how much the vibration difference would be in terms of the overall engine balance but can it really be worse than my current situation with an explosion happening at the wrong time??

The vibrations are from by the imbalance that’s caused by the cylinder in question not firing (yes that’s called a misfire) weather it’s from lack of spark, fuel or compression It doesn’t matter. Good luck.

 

[Salonika]

Misfire can also result from a delayed firing, from a weak spark, incomplete / late combustion.

I made it home……lots of oil leakage from lower end, possibly from crank seal. Diagnosis not started yet…….oil level was fine but I never had anywhere near that much leakage before this incident. The power loss was rapid, whatever was happening got way worse within 500 miles of continuous driving. I ended up limping home by manually downshifting into 2 to keep 50mph. Possibly toasted one bank cat and the downstream one as well…….

 

[MontySquareo]

Did you find the cause of the misfire?

 

[Salonika]

Diagnosis / tear down starts this weekend.

 

[Salonika]

All the spark plugs looked the same (all were WAY overdue for replacement, but they were all the same). Spark plug wires all tested fine. The number-1 cylinder intake however definitely looked LEAN (see photo). I’m heavily leaning towards injector malfunction. My injectors are original so 25yrs old and 235k on them. Perhaps time to replace.

 

[MontySquareo]

While you're in there I would compression test the engine, just for fun.