1994 Explorer Knocking/Clacking affected by Coil #6

[Anya]

I have a neglected '94 Explorer with a 4.0 OHV engine, my brother and I are rebuilding.

My issue appeared after fixing warped heads. A loud, almost a tin can clacking sound started somewhere on the drivers side of the engine. We've also changed spark plugs, wires and the ignition coil, but the sound remains the same.

The most notable issues;
Under load, there's a loss of power, engine runs rough and the sound gets much louder(but revving in neutral the sound remains relatively the same.)
The clacking seems to speed up the higher the rpm.

All these issues go away completely when coil #6 is unplugged.

Any suggestions and should it run so smooth with the coil unplugged?

 

[Turdle]

Triple check the firing order ( spark wire placement on coil) on the driver side of engine. Believe me , it is very easy to get them mixed up. I've mixed em up, and just about everyone here with a 4.0 has.

also, check for exhaust leak on the rear driver side ( number 6) port. Exhaust leaks make a banging sound that get worse with load.

Can you get a video of sound and post it to youtube?

 

[Anya]

Thanks for the response. I don't have a recording of the sound (though I wish I did) and I'm hoping when we put the Explorer together it's not duplicated.

I think we might have found the problem...

We decided to make a quick double checked of the timing, look for exhaust leaks and started to take it apart to check the injectors and he happened to decided, to double check the torque on the bolts for the rocker arm.

This is what we found...

I'm not sure what damage this could have caused, but I'm hoping fixing this solves the issues...

 

[shucker1]

That sir, a broken rocker arm tip would be the source of you noise..

 

[Turdle]

Still trying to get my head around why pulling the #6 wire would make it quiet though.

 

[Anya]

Well...upon further inspection, the valve lifter for the exhaust on #6 is stuck in the upward position, and it is realllly stuck... maybe that's why? Could have been hearing the combustion?