I've got a 02 fx4 supercrew that has almost 260k on the clock. I have put right at 30k miles and owned it for 2 years. The truck has had a knock that has me stumped and frankly still runs good so I haven't really been worried. It definitely has the cold start rattle indicative of piston slap. After running for say a minute or so it will remain quiet for a few minutes. Shortly after develops a pretty noisy knock that goes away only when completely hot. I have put a stethoscope on the oil pan and timing cover and it is quiet. Only noise is from exhaust manifold and in the cat. I have already done the stud repair thing on one side. Noise is on both sides. Is this a wrist pin noise or am I overlooking something? Quite embarrassing when it sounds like a diesel but I knocked down nearly 17mpg on a 800 mile trip 2 weeks ago.

 

Double post

 

Cold start rattle is likely worn timing chain guides. These are plastic.
Improper oil or filter will kill these. In fact the ford filter for your truck was specifically designed to eliminate a problem with these not receiving correct oil pressure to remove Slack on Startup.

Rotate each piston to TDC, then past slightly to where it is starting down., and push down on it with a screwdriver through the spark plug hole. You will feel/ hear a click if there's any play .in a bearing or wristpin.

 

I will try the screwdriver thing to check for play. Been putting that off but I am about due for some plugs anyway. I always run motorcraft filters. This sound is not a timing chain rattle. It's not consistent with cam speed and is not quite as deep of a sound as bottom end knock.

 

I would check and see if your trans is making the noise. My trans makes a little rattle at startup that goes away when it is warm, and it has 244,000 miles on it..... expecting it to kick the bucket anytime now.

Otherwise, MBB is spot on with checking for piston play.

 

I will check the flexplate out. It's so hard to narrow this noise down except it's loudest in the cats and in the manifolds. Getting ready do do a trans and engine build soon. Cant seem to find a truck in my budget that I would want and I ain't going down the 3v road for a truck. Probably money ahead to totally rebuild this one and drive it.

 

Yes, I agree. The 3V is the biggest turd Ford ever made.

 

Answered wrong post......