Strange knocking

[FormulaNascar]

Hey guys, first post here. My 1989 Ranger 2.3 5spd has been making a strange knocking sound lately. It seems fast for a rod knock but definitely sounds like one. There is no loss in power nor can I "feel" the knock. I did recently clean the egr which was clogged and the knocking totally disappeared. It came back gradually. Then I changed the plugs and wires with motorcraft parts. Went away and gradually came back. Tried higher octane fuel. Same thing. I'm at a loss and don't want to ruin my engine. Any ideas?

 

[RonD]

To rule out Rod Knock you can do this
Have engine warmed up
Turn engine off
Unplug the Intake side Coil pack, the 3 wire connector
(Just FYI for the 2.3l/2.5l dual coil engines, only exhaust side coil pack is used when starting, intake side comes on line above 400RPMs)
Start engine

Rod knock noise comes from the cylinder firing After TDC when loose Rod bearing has a gap between rod and crank, when cylinder fires that gap is slammed closed and makes the "Knock" sound.
If you can't hear the knock at idle then this test won't work

Using insulated pliers pull off one spark plug wire at a time from the coil pack
Engine will miss of course but if Knock goes away then that cylinder does have a bad rod bearing........BUT..........
An exhaust manifold leak can sound similar to a Knock, and it too would go away if cylinder is missing, so grain of salt, check for exhaust leaks at exhaust manifold

 

[FormulaNascar]

Thanks for your response. I was thinking about exhaust manifold next. Would a leaky manifold cause an intermittent knock? I'll run that tea and see what happens