My 840's cats are failing and causing quite a bit of back pressure. Needless to say the price of new oem cats is insane. Has anyone changed their cats? If so can your recommend a model? Or does anyone have a set they would be willing to sell?

-Douglas

go with MAGNAFLOW

I looked at the magnaflow site and the one they have is straight in straight out. The cats on the 840 have a slight angle out. Do you know if they will fit? It is pretty tight up there. Did you put magnaflows on your 850? If so, which one? Any issues?

Thanks

Douglas

I was going to do the MAGNAFLOWS on the 850, but found a pair of extremely low mileage cats that I welded in (someone cut the pipes off so it wasn't a direct bolt, unbolt job). I know that the MAGNAFLOWS are shorter than the stock, so your muffler guy should be able to match them up with a section of pipe.

I got the cats replaced this morning. I went with CATCO cats. The shop I used reported some problems with Maganflows not holding up. So far so good. Here's a quick rundown of the problem in case someone else has similar issues.

The check engine light on my 840 (1997 with M62 engine) came on a while ago. The errors only happened at full throttle. It was reporting fuel injector and missfire issues on cylinders 1 and 2. Later it moved to 4 and then 7. Same code. Once it threw a code, the engine would idle rough. If I turned the car off and back on it would idle fine. Also, if I drove a long distance at fairly constant speed it would idle rough when I got into city traffic. Again, I shut it off and restarted and it ran smooth.

We chased the problem by moving ignition coils and fuel injectors but the codes did not follow the componets as they moved. The codes seemingly moved around at random. My mechanic recalled a similar issue on a 540 and it turned out to be the cats.

I removed the cats and they were clogged. The ceramic had not broken up, but it was loose. The material surounding the ceramic had broken down and was now clogging the cat. Quit a bit of it poured out of the cat when it was out of the car.

The car is running great now and has a lot more power. Nothing like a clogged exhaust to lower HP. I need to drive it a bit more to see if the computer gives me anymore codes, but so far so good. I will post an update if I have anymore issues. Otherwise, consider the problem solved.

-Douglas

Interesting. We just had a very similar situation with our Benz. It was throwing similar type codes. The cats were rattling all of a sudden. Anyhow, changed the cats and all is back to normal.

Cheers

PS. Glad to hear that your case can now be considered a closed case!