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50 years of Mercury Cougar 1967/2017
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Like the title says, 2004 V6 4.0 Mountaineer, 170,000 miles.

Its stalled and had to be towed.

The next day it started up and ran rough for 2-3 minutes and stalled.

It does the same every day.

About the 80,000 mile mark almost the same issue happened.

Ford fixed it under emissions warranty, broken medium in the drivers side cat, accompanied with a loud rattle sound.

Are the odds this is the same problem or is there a worse problem (timing chains)?

Thanks Rick
 

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That sounds more like a timing chain issue. A clogged cat usually comes on slowly, and I've never seen one clogged so bad that would prevent it from idling. Considering how notorious the SOHC 4.0 is for timing chain issues, that's what I would bet on it being. And also considering how notorious they are for transmission issues, I wouldn't sink any money into fixing it either, just go buy one with the V8.
 

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Our 2004 Crown Vic Police Interceptor eats catalytic converters.

We bought it with low miles and a bat cat. Had the dual cats replaced with single aftermarket California ones. The left side went bad in under a year, had it replaced under warranty. It went bad again. Finally stopped rattling (assume all the pieces fell out), but now it's rattling again. I think it's the passenger side this time.

That's 4 cats in 50k miles. None of them has thrown a code (knocks on wood). It appears some cars just go thru them. Good luck with it!

Al
 

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Our 2004 Crown Vic Police Interceptor eats catalytic converters.

We bought it with low miles and a bat cat. Had the dual cats replaced with single aftermarket California ones. The left side went bad in under a year, had it replaced under warranty. It went bad again. Finally stopped rattling (assume all the pieces fell out), but now it's rattling again. I think it's the passenger side this time.

That's 4 cats in 50k miles. None of them has thrown a code (knocks on wood). It appears some cars just go thru them. Good luck with it!

Al
Either you replaced the cats with cheap-o ones, or something else is wrong. My whole family has those cars, and run them to very high mileages. My mother's 06 Town Car I had to replace one cat around 240K miles, and that was only because the intake started leaking, and caused a misfire, which she drove on for a couple days, which caused the cat to throw an efficiency code, and I also had to replace one on my grandmother's 04 Grand Marquis because she ran something over in the road and tore a hole in it. Other than that, my aunt's 05 Town car has 195K on the original cats, my uncle's 05 Grand Marquis has 375K on the original cats, my mom's Town car has 275K on the original left side cats, and my grandmother's 04 Grand Marquis has 115K on the original right side cats.

When I have to replace cats, either on my own car or on a customer's car, I run the magnaflow direct fit cats, and I have never had one of them fail with less than 100K miles on it.
 

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I replaced them with good "California" ones, guaranteed to not throw a code. I think they were Walker, they are very long and heavy, the rear o2 screws right into them

The car runs like a top, doesn't burn a drop of oil. We got it with 10k miles, now it has 50k. Like I said, we bought it with a rattling factory cat. We assumed it was from excessive idling. Maybe it runs a touch rich and it burns up the cats?

The CVPI's are not known for great gas mileage. The wheels are HEAVY! It has always gotten 17 city and 23 hwy (going 75+ MPH).

Al
 

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Sorry, but walker cats are junk. The "california" aspect has to do with how much platinum and palladium they have in them, but has no bearing on the quality of their construction, and walker's products are meant to get the car by for a little longer. Buy the magnaflow direct fit cat, and you won't have any more issues.
 

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I'm not buying anything, unless it throws a code. I want to pull the rattling side off and get the pieces out of there to stop the rattling, but laziness has prevailed thus far. It did just start rattling.

I thought all aftermarket converters were junk? They only cost a fraction of what factory ones cost, they can't have too much of the precious metals inside.

On the original exhaust, the 2nd cat on the left side was the one that was rattling. I can't verify if the other three were actually blown or not, they're long gone.

Al
 

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I just went through bad cats on my 03 Expedition and it would never stall. It bogged down after 2500 rpm and was hard to get over 45 mph. It was blowing the DPFE hose off the pipe that runs from the EGR to the manifold off too. They went bad after misfires due to the intake leaking coolant into the spark plug wells. I replaced the whole assembly (4 cats) with the Magnaflow unit and a straight through Magnaflow muffler and the truck pulls harder than it ever has in my possession. It has been about 2 months without a hiccup.
 

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Yeah, if I go to the trouble of pulling the pipes off, might as well throw some new Magnaflow's on there. I do already have a decent amount of money into replacing exhaust parts on this car, also put a new factory left muffler/tailpipe on there to replace a cheap muffler that a shop put on that rusted out in less than 2 yrs.

I like the sound of direct-fit bolt on parts. Saves going to the muffler shop and ending up an "aluminized pipe" victim.

OP, climb underneath the car and bang on the cats with a crowbar. They will make a vibrating noise if they are coming apart.

Al
 

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Okay, I need to do something about the cats as it's driving the wife crazy.

I need to figure out why the cats keep going bad on the '04 CVPI. Never had a code for it, just rattling. One was bad at 10k miles when we bought it, and the replacements have lasted less than 2 yrs each. The best idea I have is to replace all four o2 sensors, and either try punching out the offending unit, or throw two new Magnaflow catted downpipes pipes on there.

I hate to spend too much money on new cats cause of the likelihood they will go bad again. The Ford dealer I bought the car from had two other CVPI's just sitting in the lot. Not sure if some parts got mixed and matched between them. The mileage checked out, the car just never got driven much apparently. The car runs excellent otherwise.

Al
 

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They both failed within 2 years because that is about twice as long as the walker cats are engineered to last for. Unless you have a misfire, or you smell raw fuel coming out the exhaust, there is nothing wrong with the car, and buying the Magnaflow cats won't fix once and for all.
 

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buying the Magnaflow cats won't fix once and for all.
Hopefully you meant to say will fix once and for all!

It has been the left side all three times. For the time being, I am going to pull the left pipe off and hopefully shake the loose piece out as it's as loud as it's ever been. Then if (when) it rattles again I will put some new Magnaflows on both sides.

Al
 

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I actually meant to type "nothing wrong that buying the magnaflow cats won't fix", but my iphone must have changed "that" to "and".

If it is rattling, but not throwing a code, then you aren't going to be able to shake the loose piece out. The catalyst brick is surrounded by a fiberglass type insulation that locates it in the pipe and keeps it from bouncing around. If a chunk of the catalyst fell off and was bouncing around, you would definitely be throwing a code, and you would also be down on power since it would obstruct the flow. What actually happened in your case is the catalyst brick is still intact, but the insulation between it and the metal pipe broke down or burned up, and so there is room between the metal pipe and the catalyst brick, which rattles. If you want a temporary solution to minimize the rattling, get a large C-clamp and crush in a few spots around the center of the cat to take up the room of the missing insulation so that it won't have anywere to go, and won't rattle. The good news is you can do this on the car without even taking it down.
 

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Some loose pieces came out of the factory one, and ended up in the muffler. It was just as loud bouncing around in the muffler as it was in the cat-con. That was solved by replacing the muffler.

Al
 

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Actually, now that I think about it, since they are 2 separate cats on each side, one could break up and if the other one was still good, it wouldn't throw a code.
 

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When the original rear cat on the left side went bad, it didn't throw a code because it was behind the 02 sensor.

Currently, there is just one on each side, the Walker Ultras, with the rear 02 sensors screwed directly in them.

I am close to pulling the trigger on a pair of the Magnaflow catted downpipes. I need a permanent fix, not a 1, 2, or even a 5 year fix.

Al
 
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