I've always heard/read that when a pre-cat fails it tends to plug up, driving boost down and temperatures way up. Can the internal ceramic material be 'blown out', too?

I'm seeing a boost spike that wasn't there before. 74K miles on completely stock setup and I've checked the pre-spool/wastegate related hoses, connections, and valves. The spike problem has appeared over the last 500-1K miles.

Because of the miles on my car I'm wondering if the pre-cat might have started to crumble, but instead of clogging like normal maybe its being blown out and in the process has actually reduced the backpressure a little. Other posts always mention super-high under hood temps, etc., but I’m not seeing anything like that (at least not yet).

If the pre-cat is failing, but not clogging, I guess its filling the main cat with ceramic trash, too? Can this be cleaned and/or dumped out?

When the pre-cat begins to fail how long does it last before going toast? Am I on borrowed time?

 

borrowed time. As pre-cat fails, it typically will have the "core" of the ceramic material break free of the sides of the casting and shift back an inch or so. This doesn't create too much back pressure, but then the heat starts burning off the ends of the material, and it starts to break up. The super hot chunks blow down the pipe to... yep, the $1321 (stock, I think) main cat.

The other failure for cats is stopping the flow of air from the air pump (clogging due to HC build-up), but this is not the case with the pre-cat. You might have luck pulling the O2 sensor and looking down the hole with a mirror and little pen light. You should be able to see the pre-cat core.

Why not replace it with a DP?

 

FDJunkie, (dave)
Ive also heard of clogged PreCats glowing red at night after a good romping.

 

LOL! Yeah, right!

 

Eric, I thought that nifty red glow under my car was just the way our HOT FD's came from the factory.

By the way, were you out hot rodding on I35 last weekend? I could of sworn I heard your car make several hard passes.

 

hehehe, man since the boost gauge, Ive been testing out my boost controllers, Ive been 0-100 atleast 30 times in the last few days. and still tryin to get it exact!
BTW, my buddy blew up his MB and already has it back with a REMAN engine. There have also been more guys locally go Single T.
Hows yours?

 

I've been driving back and forth alot with the new job in Springfield, so I'm putting on more miles than I like. Will be relocating soon so I can get back to serious FD'ing. My list of planned mods is growing...

Other than the boost spike I'm seeing now, the car's still running well, and gets about 21 MPG at the "excessive highway speeds" that I've been driving.