2004 F-150 5.4L 3-valve, 73,000 miles:

Ok, now I've never had a problem with the catalytic converters, certainly not two at the same time. The dealer I went to is going to replace them free of charge, so no complaints there, and at $2,000 per CAT, I'm not complaining! The codes coming out were P0420 and P0430, cats below efficiency threshold.

I asked if there was a problem upstream, like oil consumption or leaky fuel injectors, and the response was that they weren't going to just replace the CATS for free if there was a problem upstream.

Ok, I suppose not, BUT HOW DO TWO CATS JUST DIE LIKE THAT FOR NO REASON???

My thoughts are that the CATS are probably suffering from chemical breakdown, due to excess oil or fuel in the exhaust stream. The oil I'm not sure if there is anything I can do about it for now, but wondering if I should replace the fuel injectors.

Thanks!
Matt

 

Actually they will because they have to do so. Emissions equipment is warrantied by law up to 100K miles for some items and the manufacturer has to replace them.

I would press them on the issue to make sure there is nothing else wrong.

 

Can be several reasons for early failure of the cats. The continued use of an oil based cleaner that folks use to clean the "carbon" from the intake and such. The oil coats the media and it's done. A steady supply of short drive cycles not allowing the cats to reach full operating temp which causes them to carbon the media. The use of a leaded fuel. You have to be careful where you buy gas these days. It's a common practice of stations that have flooding to get the gas pumped out of their tanks and be "recycled" which means that could include the use of tetraethylene (lead). This is usually wholesaled out to the no-name gas stations. MTBE, where included in the formulation, can also crystallize in the exhaust system and these crystals will form on the media in the cat as temps don't get high enough to burn it off. If there is a mechanical malfunction especially in the injectors can cause the cats to die. Some of the performance chips run the system too rich and the cats don't get hot enough and are overwhelmed. The list can be huge as to why. If you fit in any of the above, now ya know.

 

I've been running my truck bone stock with no modifications for almost five years now, original everything. Don't think I've been buying bad gas all these years, not sure if rabbit starts should cause it either. Just don't want the new cats to die like the old ones because I will be out of warranty when they do.

Wondering if I should replace the injectors, tried pulling the rail out last weekend but the injectors won't come out now, charge up the rail to look for leaks, but could not pull them out of the manifold. Oh man!

Thanks!
Matt