2000 Ranger Knocking at Idle
 

Any help would he appreciated I just can't figure out where the noise is coming from or what's causing it. Only happens at idle about 20 seconds after its started. I started noticing the noise after I got a cheap oil change at Firestone. I drove about 1,000 miles on their cheap oil before I found the time to swap it out for the good stuff. Check engine light is throwing P1309 which is engine misfire detector monitor not enabled. This happened after I had the shop swap out my squeaky camshaft synchronizer. Computer shows no misfires. New spark plugs, alternator, serpentine belt, brake lines, power steering lines, power steering rack, water pump, PCV valve. No metal shavings in oil. Already seafoamed the injectors.

Video with the sound-

Welcome to the forum

Could be exhaust leak, they sound like a knock.

If "cheap" oil filter didn't have a back flow valve then oil can drain out of engine passages when it sits, so start up is "dry" until oil is pumped up through engine passages, that will cause knock noise, and of course not good for the engine.

You can test for that
Turn key on
Push gas pedal down to the floor and hold it down all the way(turns off fuel injectors)
Now crank engine, it won't start but will pump oil into engine, count to 5 and stop
Release gas pedal and start engine
See if it still makes the knocking noise

If it doesn't then you do have a lack of oil knock, assuming it does knock when you don't do this

My 4.0l OHV has 350k on it and I do this routinely now, lol, bearings are getting old, so I want oil pressure built up before starting

Thanks for the reply. I tried what you said, pushing the pedal all the way down and cranking it for 5 seconds and once started it was the same. I'm hoping its just an exhaust leak, the entire exhaust system it rusty from the manifold to the muffler. But wouldn't that cause the computer to throw an oxygen sensor code? One thought stuck in the back of my head is that the guys at Firestone dropped a nut or something in the oil pan. I should have dropped the pan when I was changing the oil.

O2 sensor is not(can not be) used until it is above 600degF, so exhaust manifold leak that seals itself when heated(i.e. goes away after a minute) wouldn't show up on O2.

Even after driving for a while when I come to a stop and let it idle the noise continues.

I would be checking the oil pressure. Sounds to me like a weak oil pump at idle.

The oil pressure stays constant, you can see it at the end of the video I posted. That is if the gauge is working properly. I only saw it a little low when I started it up a few days ago when it was -2 outside but went right back up after warming up. How would I test the pressure without using the gauge?

Also, the coolant temp fluctuates while driving which could either be a bad thermostat or air in the cooling system. Never goes above normal operating temp. (after the trouble I had with a blown head gasket on my last vehicle I've been putting off touching anything that involves coolant) Could this possibly be making any sort of knocking noise?

Yo I know this thread is old but I'm having the EXACT same problem, did you ever get this figured out?

nope. I ran that truck to about 200k miles and then had to junk it due to rust. The knocking sound never went away but it never caused any problems.