My 01' 5.4 4X4 has a nice rattle at idle coming from my cats. Always worse when cold gets quieter when warm no notibeable noise under any throttle.

I've checked and it's not an exhaust leak at the manifold or anywhere else. Nor is it spark plug issues.

I've read posts untill I'm blue in the face about highflow cats and deleteing the front cats but the posts never really have any long term updates about CEL's or even pictures of how it was done.

Also from my online search short of Ford it looks like no one offers a replacement set of direct fit cats for a 4x4.

Does anyone have any info or help?

 

There are a number of companies that offer direct fit cat assemblies for left and right sides.
One is Walker.
Whatever cat pipe you get make sure the rear Ox sensor has about the same angle as the original so there is no interference with the Cab floor.
The cats have a coated fine ceramic honeycomb substrate that can break up into smaller chunks.
These move with exhaust pulses hitting them.
Check to be sure the covers around them are not coming loose.
Good luck.

 

Cut all 4 cats off replace them with magnaflow 94306 ( its the quieter one) you shouldn't have any issues with a cell. I used 2 mandrel bent 45 degree angle pipes in place of the front cats. the sound is great in the powers to.

 

Check the cover. Thats what mine is. Driver's side rear i think.

 

My 1997 truck does the same thing, rattle at idle only. There is a metal ID plate on the cat itself that fell off and is stuck between the cat and heat shield.
When the truck is cold, start it and crawl under there to determine where the noise is coming from. If you can silence or mute the noise by putting your hand on the heat shield, this could be your problem.
If the heat shiend is just loose, you should be able to fit a stainless hose clamp around it to hold it steady.

 

Yeah I messed around with the heat sheild wasn't the issue there either.

Anyone have any after pics of their setups?

 

Usaualy cats arn't to bad. Some dogs though can get noisy. I guess a meeowing cat whom meeows more than usual can get noisy. Is yours like that. What kind of cat is it?

 

Yea mine you couldn't really tell. Have to mess with it when it makes the noise. But use something to cover your hand. It does get hot.

 

Great posts in this thread, well, 99% of them.. So, I'll add a few experiences and info.

Ford TSB about rattle/chirp = heat shields. Wrap w/7' band clamps. Have the TSB if needed.

Works for awhile, but after 2 spot welds break, clamps no longer help. At this point, I grabbed the damn things and removed all shields. No more noises, but I was shield-less, no heat sink. Personally, IMO that was okay since Ford uses a hefty heat barrier just above the system and under the cab and firewall.

It may have been mentioned, the rear converters tend to crack with age, across the bottom. You can't see this unless the shield is removed. Just something to look for.

Our old converters are made very well, much better than replacements you can find anywhere today.

They're also worth a lot to salvage yards which pay approx $200 for a set from these model years. Right, you can make a little money offing the old and replacing with one new 0X compliant converter. That's doing your own work.

 

Yea, the heat shields can fool yuh and usually do.

Yea, what do you want to see? lol.

 

I may just knock the heat sheilds off with the die grinder for what it's worth.

It really sounds like the cats to me and is always loudest cold and when under the truck, It doesn't seem to get any louder with RPm which is why I don't think it's piston slap as some friends have hypothized. It's also only got 150,000kms and runs great otherwise.

 

And piston slap goes away after it get warm

 

A bad spot weld on the shield will cause allot of metal tinging upon cool down. You'll hear this almost immediately after shut down and it will carry on for about 5 minutes or so.

From cold start, you may hear it as well. It's just harder to hear with the engine running.

Another clue that it's a noisy heat shield. While @ operating temp in D, foot on the brake. They can get noisy in that circumstance. You can remove your foot from the brake , roll forward, then re-apply brake. With a bad spot weld, they tend create a chirping like sound during this test.