Catalytic converter failures

[Silverback]

My beater car is an 05 Grand Marquis with 105K on the trip meter, bone stock.

At 76K both Catalytic Converters gave up the ghost, rattling, sounding like a big exhaust leak (none) and threw a P0420 code. The CAT's were replaced, at great expense, by aftermarket parts. I didn't know about the 80K warranty and the shop didn't mention it, mea culpa.

So six weeks later the new CAT's fail in similar manner, rattling, sounds like an exhaust leak and P0420 CEL code. I took the car back to the shop for warranty and while they honored the warranty they told me my car was the problem and not their CATS and what I needed was a tune-up.

So.......I changed the plugs, COP's, air filter, fuel filter, scanned the computer for thrown codes but found none.

Almost like clock work the 2nd set of new cats failed. Rattling, sounds like an exhaust leak, although there isn't any, and threw a P0420 code CEL.

Well I continued to drive the car about 20,000 miles with the rattle, crummy sounds and Check Engine Light on.

However, I'm letting my new Daughter-in -Law use the car for her transportation piece while the wife and I look at new SUV's. But I don't want her driving around in a ghetto sounding machine so I'm going to replace the CAT's a third time. I somehow feel they are going to fail too.

Any recommendations on what I should be looking for or at?

Thanks,

Pat

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[Angus]

I would have gone catless after the first time.

You can then either tune out the cel or find some sort of device to fool the ecu.

 

[Silverback]

I received an informative response from "Logizyme" over on CV.net and it seems my car is putting too much fuel into the CATs. Until I trace that problem down and note an increase in gas mileage, putting in new CATs will just insure their destruction.

This car will not get a lot of money put into repair, it's not a reliability issue, starts right up gets 25/26 MPG on the highway, it just sounds bad.

I'll try injector cleaning and MAF cleaning next.

 

[Pewter-Camaro]

I've never had a set of Aftermarket Cats last more than 9 months.

 

[Turbocharged400sbc]

x2 aftermarket cats are really only made to last a year or so, OEM parts must last 80k by federal mandate so they have much larger amounts of paladium platinum and rhodium to process unburned fuel and NOx

being that you were at 75k ish i woulda probably tossed in new upstream O2's as after 50k they are virtually assured to have skewed off of stoic at the 450mv point.

if you a fan of the higher zinc diesel truck oils to help protect your motor that will also hasten the demise of the cats but help the engine live alot longer (manuf could give a shit, just so long as the motor lasts to 100k nowadays)

take a look at the plugs and see if one of em might be getting excessive fuel/oil on em, you can also look into an air/oil seperator on the pcv line to the intake if excessive blowby is introducing oil that will accelerate killing the cats.

either blow the big bucks for oem cats or keep this up every year with the cheapo's

in cali it was far cheaper to grab a 100$ cheapo toss it on for the emissions test, yank it off and toss the old one back on, set the new cat on the shelf... and repeat every year....fuck those tree huggin nazi's out there

primarily youll be looking at the primary O2's, plugs and dep on the plugs a leakdown test or possible injector/s

 

[Silverback]

Thanks for the good info, straight line thinking some times doesn't work for the OBD2 cars.

So...... check the plugs for fuel/oil contamination (My Marauders heads was just repaired for that very problem).

Add an oil separator, for the Marauder too.

replace primary 02 sensors

Question - wouldn't the EGR system also aid in providing contaminated exhaust into the cylinders via the recirculation path?

 

[Turbocharged400sbc]

if there's and effect, there's a cause

egr isnt gonna have any measureable effect except for carbon accumulation. it isnt a large volume being recirculated, though when its active is typically during cruise conditions where intake vacume might encourage oil to leak past valve seals on the intake side.

look at the plugs firt and go from there, dont buy new cats or o2's just yet