Catalytic converter keep going out

Have a 99 3.4L. Every 2 years my cat does not pass emissions. This is the third one I have put in. Now they have been the universal kind because they are so expensive.

The first time it went out I had the O2 sensor replaced because of a cel light. Truck has 250,000 miles and the engine runs fine. The valve cover gaskets were leaking and I just had them replaced. Any ideas?

 

First off, cats don't die over time. They are killed by something. Even if there isn't a CEL there is probably something going on in your engine burning up the cats. Long story short take it to a competent technician familiar with smog related engine issues and have them diagnose your problem.

 

The tech at the muffler shop said it looked like it might be running rich. He said that he has not seen this situation before. If no ideas come up I will take it in.

 

It could be running rich, or burning oil. How often do you have to top off the oil? It would be a good idea to take a look at your spark plugs as well. Do you know the last time they were replaced?

 

Good point on the plugs. I think they have quit a few miles on them. Burns about a quart in 5000 miles.

 

The spec for plugs on the 3.4 is 30k miles, if it's been longer than that I'd change them for sure. And the condition of the plugs can be a good indicator of how the engine is running.

 

there you go, burning oil and running rich because plugs are fouled. you will also need o2 sensors that the burning oil has clogged up im sure.

and when was the last time you cleaned the MAF sensor and throttle body? check the air filter too, that's about the best you can do short of engine rebuild and/or replacement

 

loosing any coolant at all ? coolant will take out a cat and an O2 sensor in short order

 

Well now I am embarrassed. I bet those plugs have around 100,000 miles. Air filter gets changed often. Looks like I have a little maintenance to do. Thanks for all the quick replies everyone!

 

Not loosing coolant.

 

make sure you use the correct plugs as well.....

$18 Denso K16TR11 Spark Plugs, Pack of 4

Denso K16TR11 or

$8 NGK BKR5EKB11 NGK Spark Plug Stock # 3967

NGK BKR5EKB11

 

Yea ^this. Don't go after market, just buy the ones from the dealer.

 

You guys are awesome! Love all the comments.

 

Rock auto would be good, cheaper than dealer or parts store, and look at the picture so you know what you're supposed to be getting, I've had them send the wrong ones in the past ( pulled by item stock number not part number ordered Denso, got NGK, totally different plug )

 

If you are not running at 14.7 afr at cruising you will kill your cat converter sooner then later.

Additionally, a rich situation will not kill a cat converter anywhere near as soon as a lean situation would. Fuel being dumped through the cats actually provides a cooling situation to them so I would not necessarily rule out an overly rich situation but I wouldn't be looking that way first. Oil burning would hurt the cats so hopefully you aren't burning oil.

Fact of the matter is that universal cats are not a proper solution for a cat converter replacement when it comes down to it. On certain vehicles they sometimes don't even provide emission compliance. I know this is not what you want to hear, but if you want to do this correctly and not have to worry about it again for a while, fix the AFR issue you are having, have the shop working on your vehicle or testing it test emissions before the cats to ensure that it is within acceptable ranges (hell, it could just be a tune up you need) and replace the cat converter(s) with OE.

 

Save your money and don't buy from Rock Auto. The use cheap generic parts and they have zero customer service. I used to support these guys and after a couple of bad experiences I would recommend anyone other than these guys.

 

there is this too....http://www.rockauto.com/info/EasternCat/Converter Break In flyer.pdf

converter "break in"

 

Youre running rich, i dont know how, could be a chronic misfire, but id put it at 90% likely. Thats the only thing that will kill a catalytic that rapidly.

 

I can't say that, ordered radiator, was crushed in transit, new radiator next business day, no return nessesary, same with the plugs, made the call, took all of 4 minutes once I realized what had happened ( item stock number confusion )

and they don't sell any cheaper of parts than any other parts store, and you have the choice of what you want in many cases. sometimes offering OEM manufacture parts as well ( Denso and Aisin in Toyota's case )

 

Make sure you replace your PVC valve and grommet if you're consuming oil, they will plug up. Plus, do a Sea Foam treatment on the truck before you work on it. It will help you out with cleaning injectors, upper cylinder heads and freeing up possible sticky piston rings, because burning a quart every 5K would bother me. Just my .02cents.