Fixing blocked exhaust

[rowan194]

My fuel consumption has been higher for months and the exhaust "warbles" at certain revs, almost sounds like a V8. I've finally got some time and $ to fix my exhaust, so...

Should I replace the cat first ($130ish on ebay) ... (I undid my exhaust manifold at least 3 or 4 times, wedging a box under the cat to hold up the exhaust connection, so I wouldn't be surprised if I damaged it)
OR
Replace everything past the cat first? ($230+ on ebay)
OR
Try the middle muffler first, then go from there?

Budget is still limited (my wife has written off two cars in the past 9 months!!!!) so I'd rather not have to do everything past the manifold.

[rowan194]

Hmm, maybe I didn't give enough info. Regulars may remember mention of it from several months ago. Basically, the exhaust makes more noise (deeper grumbling, not a misfire), and it seems to be running hotter (can smell "hot metal" from the engine bay vicinity after a reasonable trip)

So it could be a blocked cat, or the cat bits have all gone further down and blocked the mufflers. I can't find my non contact thermo to compare in and out temps of the cat and mufflers.

I guess replacing the cat would be a good start, since if it's shattered there could be potential for more crap to come out of the existing one? Or would a blocked muffler be likely to damage the new cat?

[XP6]

It would be unlikely the muffler or a pipe is blocked unless they've been hit... pretty unusual to block a cat too, normally they just decrease in emission performance or the matrix physically collapses, if so it will rattle heaps.
Have you checked the whole system for physical damage?

[rowan194]

Here's a thread from 7 months ago (lol, has it really been that long)

http://www.fordforums.com.au/showthread.php?t=11352056

[mik]

if it where myself i would replace the cat, they have been known to block up on occasions, my mate had on go bad, it caused him untold grief trying to fix weird engine behavior, he probably replaced a lot of his fuel system twice over and ignition system (lpg included), you could always do the mufflers at down the track.

[Mechan1k]

cats can melt internally and partially or completely block.

Get it checked out first before doing anything else ... it's common on these things for them to either block or blow out.

If it has blown out pieces ... these chunks can then block up downstream mufflers if the chunks are large enough ... had something similar happen in my Territory ... luckily the bits could be shaken out of that muffler and it was able to be reused.