Intermittent knock after Engine is warm

[Haywire6000]

So a few days ago my engine developed an Intermittent knock at idle after it's warm. Only does it after it's been running for a while. Also if I rev it the knock goes away for a while. The odd thing is is that it sounds like it's coming from the bottom end ( I can hear it under the truck). Possible clutch??

 

[Frank The Tank]

My truck was doing this... After an EGR valve and a catalytic converter I checked it at night with the lights off and found a plug wire jumping to the exhaust manifold. Worth a look. It was shaking so bad I though my harmonic balancer had backed off or something.

 

[Haywire6000]

hmmm, worth a look. I have beldans so I my wires are good for life. I also heard that the 2.3l are also common for loose spark plugs.

 

[RonD]

Could be a rod bearing knocking because of low oil pressure after oil warms up.

If you remove the spark from one cylinder at a time, you can often tell, first if it is a rod bearing and, second which rod bearing.
Knock will go away if there is no power stroke, i.e. no spark

 

[the_gunslinger]

It sounds like an oil pressure issue. At idle, the oil pump isn't putting out enough to properly lubricare everything. Raise the RPMs and the flow of oil increases, lubricating properly, and quieting the knock.

There are several different knocks that can come grom the bottom end. With out hearing the knock, it's hard to say for sure.

 

[Haywire6000]

I would agree with the rod bearing BUT it doesn't do it all the time.

 

[RonD]

You have an OHC engine so don't get the "warning ticks" from lifters when oil pressure is too low, so you get it from the rod bearings, and it can come and go based on the pressure from moment to moment.

If you have recently changed the oil the new filter could cause lower pressure by limiting flow, you can swap it out to test that.
There are some additives that can clean out passages and help thicken oil slightly.

Ford doesn't use real time oil pressure gauges, so adding even a temporary oil pressure gauge to test pressure might help diagnose this problem.

 

[PanamaExpat]

Any knock is not a good knock... Get out the stethoscope or a piece of broom handle. Shouldn't take too long to sort where it is coming from.