96 4.0 OHV LOUD knock!! Ignition? Rod?

[kyleham]

OK so my son picked up an explorer sport for his 1st car. Too funny there are only a couple panels that dont have dents in them!
So it was running poorly... took the injectors out and cleaned 4 of them but 2 of them wouldn't open at all. So, replaced 2 and slapped it back together.
Car runs and idles fine.....but there was a NASTY knock in the engine. Comes from the rear of the engine, almost seems like it comes from where the engine and bell housing bolt together. The sound is everywhere. Used a stethescope but its so hard to place!!
I just read another post where the guy did the same thing. He put a video on youtube and it sounds exactly the same.He says a new coil pack fixed it.
I took off a valve cover to see if the lifters were all tight....Yep. I drained both the tranny oil and engine oil looking for metal...nothing.
Is this possible ? I am at a loss....

 

[acschilling]

I had a wicked knock in my OHV for nearly two years. Knocked rhythmically for 10-15 mins while warming up. I changed my valve cover gaskets and the knock is 98% gone; maybe 5-10 seconds if it's near freezing on its first start of the day. I had 0 play in either side of the rocker arms too. Use Fel-pro gaskets and the gray gasket maker.

 

[96EXXLTinCO]

I'm haveing the same issue on my '96, it's feelin like a rod bearing to me. I used STP oil treatment on the last oil change and it quieted it down a little bit.

 

[kyleham]

This is not my vehicle but it sounds exactly like it....

https://www.youtube.com/watch?v=fuHH90KIaSY

 

[kyleham]

Yeah, I think that guy may have lied about the coil pack to save face on a misdiagnosis
Pretty sure I have a bad rod bearing.......bummer

 

[JusTheUsual]

Im surprised no one has said anything about the back main seal

 

[96EXXLTinCO]

Im surprised no one has said anything about the back main seal

What about the rear main? What might a bad seal contribute to the problem?

 

[kyleham]

gonna pull the motor tonight....I will give a full report

 

[kyleham]

looked at all the rod and main surfaces .....they all look ok! Have not pulled the crank yet or pulled out the calipers yet either, but they look ok so far! ?????????????Cam bearings and lifters are next, on the list of things to look at!

 

[koda2000]

How's your oil pressure (check using a real oil pressure gauge). If you oil pressure is good then you knock probably isn't bearing related. check your torque converter and flexplate bolts.

Don't think you can have this problem on a Ford valve cover, but I once bought a '62 Corvette cheap, because the PO believed the engine had piston-slap. Turned out he'd installed a valve cover upside-down and a tappet/rocker-arm was hitting the underside of the valve cover. I noticed oil leaking from the top side of the valve cover and couldn't understand how that could happen. I pulled the valve cover off and saw that the tappet had worn through from hitting it. Sealed the hole and turned the valve cover over and no more noise. PO was pissed when I told him.

 

[kyleham]

OK, so the problem has been found! When I was trying to take the studs out that hold the aluminum plate for the fuel injectors, I broke a piece of the torx end of the stud off! The reason I know this is the piece is because there are 2 torx impressions in the piston and head. I was able to pull the steel chunk out. The piston isn't reall bad but the copression from the chunk made it all the way back to the oil ring. making little waves in the 3 sets of rings, pinching them all....
Boy there's nothin like causin your own problems!!!
So I think we are going to throw in some main and rod bearings and call it a day...
I would like to buy a used piston and rod assembly from someone....I dont want to buy all new pistons and press all the wrist pins in.