I have suspected for some time now that I may have a catalytic converter going bad on the drivers side. At start up it sounds like its got pebbles in it and when my engine is under load when towing there is a rattle. Today pulling out of a parking lot just giving it gas it sounded like a couple of tin cans bouncing around so it seems to be getting worse. The sound is directly under ther drivers side front.

I have 66,000 on the truck so I think it is still under warranty(80,000?). My only exhaust modification was a muffler swap and tip. It has not thrown any codes so far. I was trying to decide if I should let Ford replace it or take this opportunity to upgrade to some high flows. I have a couple of questions.

1st, Does this sound like the cat is the problem or could something else be going on?

2nd, Am I hurting anything by driving it with a bad cat? If I decide to get high flows it will probably take a few weeks to get the parts and get it on.

3rd, Anyone done the switch to high flows know what part numbers I need? Also what difference did it make in your system and would I benifit from them basically having a stock set up?

Thanks!

 

Does your truck have 2 pre cats and 2 rears? All your really doing is just wasting gas and losing a little power. Go under there and bang it with a mallet. Compare it to the one on the other side. You can take the truck to Ford and they will diagnose for free since it is covered under the warranty (8 years or 80k), that way you know for sure its a bad cat and nothing else. Could also be the heat shield being loose and rattling. If your truck has the 4 cats and you can get away with chopping all 4 off and running 2 high flows, then that is your best bet. Otherwise keep the pre cats and run 2 high flows in place of the rear. Magnaflow has a bunch of different converters, 94106 being the most free flowing (loudest).

 

Like migdaddy said, might crawl under it and bang on them with a mallet to see if you can narrow it down. There are a few heat shields under there that can sometimes rattle, but it could very well be the guts of your cat causing it.

I know on some older ones, if left unchecked they can break up the internals of the cats, then get clogged in the pipe, cutting your exhaust flow down a great deal, which can sometimes lead to other issues up the line (I bent an exhaust valve in an old dodge once with this scenario)..

So, give it a whack, and make plans to either replace with the High-Flows or go the warranty route, will make for an easier and quieter summer for ya

 

I only have the two cats, I will try to bang around on it tonight!

 

You will want them to sound solid, not hollow. Hollow will indicate that the catalyst is blown out.

 

I'm going to say its a loose heat shield. Nothing else under there can really rattle. And if one of your catalytic converters was to be blown out, you would smell it. And see a CEL.

 

Not necessarily will a CEL come on. I never had one come on from my blown out pre cat. Also never had a CEL when misfiring on 2 cylinders.

 

Remember the pre-cats in your generation resonate more than they filter, I'm not quite sure what the catalyst is for, but it isn't for killing the heavy smog. But when a cat is blown, a light will come on. The performance slug will show too.

 

I appreciate all the advice. It originally only did it occasionally while towing. In fact I first wondered if somehow my suspension being lowered by trailer weight was causing something to rub but I could find nothing and it is too far forward for that I think. It is starting to get annoying enough now that I am really going to have to track it down. I will check the heat shields too.

 

I got under the truck last night and banged on both cats. I could not tell a noticable difference in the sound of them. The drivers side might have sounded a tad more hollow but it could be that I was expecting to hear it that way? The heat shields were not loose at all and I could not find any rocks stuck in the shields either. I will most likely take it to the Ford dealer and let them check it out. I would hate to put high flows on and still have a problem although I don't know what else it could be?

 

Yeah...have Ford run a diagnostic test to let you know what your problem is. They should NOT charge you.