Knocking noise only during cold start?

[erykv1]

How many miles? Did this start all of a sudden or gradually get worse over time? Tightening your converter wouldn't help the cause of your issue if it is in the converter. You would need to replace or eliminate the converter to get rid of the chunks of material beating around in there. I have had this very thing happen to me on a Mustang and didn't figure it out until after I replaced the bearings. What you describe sounds like good old 4.0 piston slap to me.

Started randomly one day. I been having fuel pump issues so its always been a rough start during mornings, but maybe this contributed to the problem I have now.

I had someone who had piston slap before listen to it, and we came to the conclusion that it isnt.

There is 150k on the chassis, but the motor was rebuilt about 10k miles ago (before I bought it).

I ordered a bosch fuel pump today, as well as a set of main bearings. Looks like I'll be tearing into it this weekend.

 

[erykv1]

Ok heres an update from this weekend (for anyone that may search for this issue in the future).

This is what fixed my problem, can't say the same for anyone elses situation:

1. Opened up the inspection plate and found that the flywheel bolts were a TAD loose, not finger loose like what I've been reading. Tightened those up.

2. Drained the oil and did an oil change with rotella t5 10w30 and a mobil1 filter. Added in a quart of marvel mystery oil for good measure (I'm an oil additive skeptic).

3. Changed my fuel pump, old one looked nasty and wasn't keeping fuel in the rail as the check valve was bad. Unrelated to the knocking noise, but the priming every time got old.

The combination of these 3 has gotten my jeep running better, and the knock noise is gone. Its completely silent. My oil pressure is about 10 psi higher on cold starts as well. I had my doubts w/ MMO but it seems to have quieted down the valve train substantially.

Guess I will be returning the main bearings / oil pump / oil pickup tube & oil pan gasket as I wont be needing to replace those

Thank you all for your input, I will update if anything different occurs :clap:

 

[ehall]

Open the oil fill cap on top of the valve cover and shine a light inside, can you see the rocker metal or do you see sludge