Clogged cat?

[Zero Signal]

I've had this wierd rattling/knocking sorta sound coming from under the car recently. It's been getting really bad and just in the past couple of days I've lost all my power. The exhuast sounds really wierd, kind of like a 4 banger on steroids with a slight hissing sound mixed in.

After a good drive, my driver side tail pipe is warm but I can grab it and hold it where the passenger side tilepipe is too hot to even touch.

Also, I did some datalogging and found that the driver side O2 is pegged.

Scott (mo_dingo) and I took a look at it and the only thing we could think of was that maybe a piece in the cat busted off and is clanking around blocking air flow out of the cat.

Has anyone see that happen? Either way, I'm ordering an off road H. I'm thinking ofjust getting that 2 piece summit one.

 

[91LX_5L]

its prob clogged, clogged cats sound so weird and you do lose quite a bit of power. why not run a offroad pipe?

 

[HISSIN50]

The precious metals lose their tack and rattle. I have had several cars do it.

What are you gonna do for emissions?

Oh yeah, if you have a vac gauge, hook it up and hold the throttle real steady at 2000 RPM or so (just keep it super steady). If after like 10-45 seconds (anytime in there) the vac reading starts to drop (it should be rock steady), that suggests an exhaust restriction. And the likely factor is a constipated cat.

Good luck John.

 

[mo_dingo]

The precious metals lose their tack and rattle. I have had several cars do it.

What are you gonna do for emissions?

Oh yeah, if you have a vac gauge, hook it up and hold the throttle real steady at 2000 RPM or so (just keep it super steady). If after like 10-45 seconds (anytime in there) the vac reading starts to drop (it should be rock steady), that suggests an exhaust restriction. And the likely factor is a constipated cat.

Good luck John.

That is the only thing I could think of. I was hoping it wasn't something loose in the oil pan, or maybe the oil pump.

But the sound seems to be coming from the d-side pre-cat. Which correlates with the O2 data that john has pulled from the tweecer. And when he gets on the gas while driving, it almost sounds like his car is a turbo car, as sweet mellow sound out of the exhaust.

We will find out soon enough I hope. Worst case scenario, he can borrow my stock midpipe for emissions use; As I do the same thing every year.

I was thinking of shaking the h-pipe once we remove it and seeing if the piece was rattling inside the cat. Would that work, or do they need to be hot for some reason?

I figured since the cats have a mesh screen on both sides that any debris inside would stay stuck inside and rattle around.
Scott

 

[Joes95GT]

I had a cat clog about 4 years ago. I lost all power, however, there was no ratting sound and I never thought to feel the differences in the temperatures of the exhaust (or tailpipes).

My Dad looked all over for the problem (at the time he worked in a Ford garage), and he finally figured out that it was a converter. Luckily, it was covered by the 8/80 warrantee or else it was going to cost about $800 because they replaced the entire pipe.

Good luck.

Joe

 

[HISSIN50]

Sounds good Scott. Like you said, you should be able to shake the pipe on a bench and hear something. It should be a honeycomb in there with some tiny tack welds (two stage cats are really high tech. ). But it should be fairly hard to 'blow' that cat material out, unless it had completely disintegrated already.

Have you put on mech's gloves and carefully punched the cat/heat shield? I have almost always been able to make a bad one rattle doing this.

One can also drill a small hole in the exhaust in front of the [pre] cat. If air is flying out of there at like 100 PSI, that suggests a restriction.

It sure sounds like a bad one though - his comments on the contrast in each pipe's heat saturation, yours on the sound (my car sounds like it has a turbo if I put a banana in the tail pipes), etc.

Good luck with getting it fixed.

 

[Zero Signal]

Update: I ordered the Summit 2 piece h-pipe. I'm glad I finally got one cuase I could use a new exhuast note.

Onto the stock cat. . . Well I went to my parents house, put the car on the ramps and made my dad help me yank the stock h-pipe. We got it down in 15-20 minutes or so. I took his snake light and checked out the front cats. It turns out the front driver side screen had fallen into the cat and was clanking around as suspected! So I grabbed the crow bar and went nuts on both fron cats and had them gutted in no time. Slapped it all back together (with some header stud complication. . .) and the car's like new, woohoo! Anyway, just thought I would share.

One thing is for sure, bashing the hell out of the pre-cats with the crowbar was damn fun.

 

[HISSIN50]

Sounds good man. If you remember, post back with how the tone changes from the, ahem, modified stock pipe vs the new H-pipe.

I would recommend using a band clamp on the H-connection (Pep might sell band clamps locally. Not sure about Napa or Merles - the latter is my fav local parts store).
I am not a fan of welding that union together (it is welded on the '94 ).

That part might just be my personal preference.

Good luck John.

 

[mo_dingo]

Sounds good man. If you remember, post back with how the tone changes from the, ahem, modified stock pipe vs the new H-pipe.

I would recommend using a band clamp on the H-connection (Pep might sell band clamps locally. Not sure about Napa or Merles - the latter is my fav local parts store).
I am not a fan of welding that union together (it is welded on the '94 ).

That part might just be my personal preference.

Good luck John.

Just out of curiousity, why not weld it? Because you can't take it apart w/o grinding the welds or something????

If the clamp way doesn't leak, then go for it.

Hey John, glad to see it wasn't something banging around in your oil pan....Don't forget to get a 6" piece of silicone tubing for your smog tube and 2 radiator clamps. That will make swapping the pipes so easy each year.
Scott

 

[HISSIN50]

Just out of curiousity, why not weld it? Because you can't take it apart w/o grinding the welds or something????

If the clamp way doesn't leak, then go for it.


Scott

Scott, you are correct. Competant welding is the best. People's combos change so I usually recommend the Band clamps instead, since they are tweakable (I wish I could tweak them on the '94). So I think band clamps are more practical. And of course much better than the usual parts store clamps which crimp the pipe and can leak (causing rust sometimes too, even here).

But if one has a line on having a decent weld done, double check fitment twice and go for it.