As reported in This thread, I appear to have a plugged cat and/or muffler on my '86 GT. The engine runs fine at idle and it accelerates smoothly, but there is NO power at all from mid-range upwards. [EDIT] Upon closer observation, it's gutless from 2000 RPM up.

If it's the cat that's plugged, that's a simple fix with a replacement straight pipe , but if it's the muffler, that's probably a bit more difficult to rectify.

Does anyone have experience getting pieces of broken up cat out of a muffler? Can it be done successfully? What's the trick?

[This message has been edited by Patrick (edited 11-03-2008).]

Really now, do you really want to fix a 20+ yr old muffler?

------------------
87GT - 3800SC Series III engine, 3.4" Pulley, N* TB, LS1 MAF, Flotech Exhaust Autolite 104's Custom CAI 4T65eHD w. custom axles, HP Tuners VCM Suite.
87GT - 3.4L Turbocharged engine, modified TH125H
" I'M ON THE LOOSE WITHOUT THE JUICE "

You can take the muffler off and just shake it to remove parts pieces and evil hexes,,if clogged it is probably the cat
If your system is still original it is welded together
Drop it on the ground to work on it
hack saw as close to the cat as possible so you have maximum pipe to work with file or grind pipe so you have smooth surface to install new cat or pipe ..A 20 year old cat has lost its effectiveness..it is also possible parts of the cat are stuck in the pipe running from the cat to muffler
spring removal is a pain in the anal track a simple tool is just a threaded rod ,,drill a hole thru some piece of hard wood insert rod with washer and bolts then sceme what ever you desire as to the part that will hook the spring,, this tool helps prevent finger damage from vise grip channel lock pulls
I like to replace the cat and muffler with a thrush or cherry bomb,, unless you have inspections..they are quiet enough untill you get it on
remove the 02 sensor to check for clogged exhaust components

[This message has been edited by uhlanstan (edited 11-02-2008).]

quote Originally posted by Dennis LaGrua: Really now, do you really want to fix a 20+ yr old muffler?

Dennis, I suppose I could ask YOU the same thing about wanting to fix a 20+ yr old car.

1) You have no idea what the age of the muffler on this Fiero is.

2) Even if it was the original muffler, is there a reason why a 20+ year old stainless steel muffler coudn't possibly still be in good shape?

3) I would hardly consider blowing, sucking, or banging a foreign substance from a muffler to be a revolutionary and ill-advised concept. It's not like I'm wanting to cut open the muffler to replace rusted-out baffles or something.

If YOU consider it to be a waste of time, fine, I was asking advice from people here who might've had some experience doing what I had requested. Thanks.

quote Originally posted by Patrick: As reported in This thread, I appear to have a plugged cat and/or muffler on my '86 GT. The engine runs fine at idle and it accelerates smoothly, but there is NO power at all from mid-range upwards. If it's the cat that's plugged, that's a simple fix with a replacement straight pipe , but if it's the muffler, that's probably a bit more difficult to rectify. Does anyone have experience getting pieces of broken up cat out of a muffler? Can it be done successfully? What's the trick?

The only successful trick is...replace the muffler.

Like Dennis said, I wouldn't want to fix a 20year old unit. Or even if its not, your better to start with a new cat back or put a strait pipe instead of a cat. That would more cost effective, unless you need a cat when you pass emissions in your area.

------------------
fierogt28

88 GT, loaded, 5-speed

quote Originally posted by uhlanstan: A 20 year old cat has lost its effectiveness..it is also possible parts of the cat are stuck in the pipe running from the cat to muffler

Stan, my first post has a link to another thread of mine where I stated, "The cat is an aftermarket one that looks like it hasn’t got a whole lot of miles on it".

Whether it's coming apart inside or not has yet to be determined.

Stan, it sounds like you've had some experience around cats which have disintegrated. What form are these pieces in? Are they large chunks, or fine little pieces, or both?

By the way, thanks for the tip on making it a bit easier to deal with the many springs holding the exhaust system in place!

quote Originally posted by Patrick: Dennis, I suppose I could ask YOU the same thing about wanting to fix a 20+ yr old car. 1) You have no idea what the age of the muffler on this Fiero is. 2) Even if it was the original muffler, is there a reason why a 20+ year old stainless steel muffler coudn't possibly still be in good shape? 3) I would hardly consider blowing, sucking, or banging a foreign substance from a muffler to be a revolutionary and ill-advised concept. It's not like I'm wanting to cut open the muffler to replace rusted-out baffles or something. If YOU consider it to be a waste of time, fine, I was asking advice from people here who might've had some experience doing what I had requested. Thanks.

Did you know that stainless steel WILL rust and deteriorate, just slower than mild steel. You can do what you want with your Fiero but at 20+ years, stainless steel or not, IMO you'd be best served by a new muffler that will prove to be the only lasting repair. If opinions and suggestions are of no value to you and you find them offensive then I suggest not reading my posts.

------------------
87GT - 3800SC Series III engine, 3.4" Pulley, N* TB, LS1 MAF, Flotech Exhaust Autolite 104's Custom CAI 4T65eHD w. custom axles, HP Tuners VCM Suite.
87GT - 3.4L Turbocharged engine, modified TH125H
" I'M ON THE LOOSE WITHOUT THE JUICE "

Most cats use an extruded honeycomb that is easy to break apart with a crowbar for *cough* offroad use *cough*

Running rich can cause the honeycomb to melt and fuse together, partially blocking the cat. Discoloration would be the key thing to look for there.

If the muffler doesn't have any filler in it, I don't see how it could become blocked.

One thing you could do is replace the o2 sensor with a nipple and a pressure gauge and see if you get any high PSI readings. I think they sell exhaust backpressure testers for this purpose.

quote Originally posted by ryan.hess: If the muffler doesn't have any filler in it, I don't see how it could become blocked.

Ryan, I'm not even sure there is a blockage anywhere at this point. I'm just going by symptoms and observations and suggestions from other threads where this has been discussed. As I understand it, other people posting here have had their Fiero's muffler plug up from cat crap. That's why I was interested in finding out what this stuff looks like, and how difficult it might be to remove from the muffler. Yes, it may turn out to be imposssible, but then, maybe not...

quote Originally posted by Patrick: Ryan, I'm not even sure there is a blockage anywhere at this point. I'm just going by symptoms and observations and suggestions from other threads where this has been discussed. As I understand it, other people posting here have had their Fiero's muffler plug up from cat crap. That's why I was interested in finding out what this stuff looks like, and how difficult it might be to remove from the muffler. Yes, it may turn out to be imposssible, but then, maybe not...

Take off the exhaust and see if it gets better.

quote Originally posted by Patrick: Dennis, I value anyone's opinion who takes the time to post. However, I found your first post to be more condescending than anything else. It appeared to me that you were more interested in mocking my desire to unplug the muffler (if possible) than trying to actually be helpful. As stated earlier, you have no idea on the age of this muffler. It could've been installed a month ago for all you know. [QUOTE]Originally posted by Dennis LaGrua: Really now, do you really want to fix a 20+ yr old muffler?

[/QUOTE]

I was not trying to be rude and certainly never talk down to anyone. Just making a statement to provoke thought, stimulate conversation and offer what I believe is the best solution. That solution is just a suggestion and it may not be right for you but it might end up saving you allot of time and work When mufflers clog it is typically the baffles that collapse and if this happens I see no way to fix it. However. if you do unclog the muffler, please be sure to tell me how wrong I was with my analysis.

------------------
87GT - 3800SC Series III engine, 3.4" Pulley, N* TB, LS1 MAF, Flotech Exhaust Autolite 104's Custom CAI 4T65eHD w. custom axles, HP Tuners VCM Suite.
87GT - 3.4L Turbocharged engine, modified TH125H
" I'M ON THE LOOSE WITHOUT THE JUICE "

quote Originally posted by Dennis LaGrua: When mufflers clog it is typically the baffles that collapse and if this happens I see no way to fix it.

This comment is at least more informative than your first post.

However, I can't remember ever reading here at PFF about Fiero mufflers failing due to collapsed baffles, whereas there have been many reports over the years of mufflers being plugged with the broken up and blown out contents of catalytic convertors.

From This recent thread:

quote Originally posted by surfkorea2001: I finally got my car running correctly, I replaced the muffler because it was plugged with material from the Cat.

Yes, in this case the muffler was replaced. That may turn out to be the best solution for me as well, but that's what this thread was all about - to find out what works and what doesn't.

I'll certainly post what I find and how I fixed it.

FWIW, I had a cat let loose on me back in 1990 ('88 GT with 25K miles). It just melted the honeycomb, so no chunks of crap ever made it to the muffler. The performance was pathetic howevere.....even though it *was* an auto. A new cat under warranty fixed that.

Fast forward a decade or so.....I bought a Fiero (I think it was another '88 GT) and the cat was bad. I pulled off the exhast system and removed that cat. It was a mess. I shook the muffler and could hear stuff rattling around. I managed to get quite a bit out, but it was still plugged up. I finally took a cutoff wheel to the case and opened her up. There was no way I would have ever gotten some of those chunks out......just buried too deep inside the muffler. I wound up installing a Borla system on that GT.


Good luck.....maybe your clog is still confined to the cat (crosses fingers).

twice in the past I've been downed by a clogged catalytic, once on an AMC concord and once on an old CRX . the CRX had to be towed and the cat replaced, we were a long way from home when the concord did it and i got the same symptoms. she would idle just fine but with even a little bit of gas she would bog and die. we nursed it to a gas station garage (you remember those dont you? :-) and the mechanic (knowing we were low on funds) pulled it loose and drove a steel rod through it. not exactly "right" but it got us home.

quote Originally posted by mrfiero: I shook the muffler and could hear stuff rattling around. I managed to get quite a bit out, but it was still plugged up. I finally took a cutoff wheel to the case and opened her up. There was no way I would have ever gotten some of those chunks out......just buried too deep inside the muffler.

Ah, that's the kind of stuff that's helpful to hear. Not exactly what I wanted to hear, but helpful nonetheless. Thanks Mike.

Just remember the test for a clogged exhaust is simple just remove the 02 sensor from the pipe if the system is clogged ,,it will run much better with the "'leak""
A car with out a cat will pass emission test much better if the engine is hot at the test,, this is very effective with the cat also ,,any emission test on a fiero should be done when the fiero is hot,, the cat is more efficient at hi temperature..so if you have to wait make sure car is hot at test
If you have a car you think will not pass.or a car that has failed ,,after doing what ever tune to try to meet emissions you can install an old hose on between TBI or manifold and vacuum control part and make a small hole in the hose with an ice pick or large pin to create a lean condition ,,Naturally you want to I D the problem later to have a good running engine ,and prevent future problems. the hole just has to large enough to circumvent the EMC

the spring puller idea needs file work to easily pull springs the rod is normally to big,but it gives people an idea of how to use what they have to build a simple spring puller,,Im to cheap to buy the spring tool
some of the original mufflers will last 30 years ,but do not count on this ..I replace the muffler on each Fiero I have owned,,and the original muffler seem to be in good operating condition

quote Originally posted by uhlanstan: If you have a car you think will not pass.or a car that has failed ,,after doing what ever tune to try to meet emissions you can install an old hose on between TBI or manifold and vacuum control part and make a small hole in the hose with an ice pick or large pin to create a lean condition ,,Naturally you want to I D the problem later to have a good running engine ,and prevent future problems. the hole just has to large enough to circumvent the EMC

Not wanting to go off on a tangent here, but Stan, I'm curious about what you've stated above.

Wouldn't putting a hole in a hose (vacuum line) simply trigger the ECM to dump more fuel into the mix because of a perceived "lean" condition? If so, how would that help to pass an emission test? Or is that why you've stated that the hole has to be "large enough" (so that there's no way the ECM can fully compensate)? But then, wouldn't the idle speed be racing?

[This message has been edited by Patrick (edited 11-03-2008).]

quote Originally posted by Patrick: I'll certainly post what I find and how I fixed it.

Sorry, I lost track of this thread.

Yes, the cat was clogged and the muffler was fine. Here's a shot of the inside of my cat when I took it off.



I gutted it and put it back on. Runs fine and even passed the smog test.

Thank-you for everyone's help.

quote Originally posted by Patrick: Sorry, I lost track of this thread. Yes, the cat was clogged and the muffler was fine. Here's a shot of the inside of my cat when I took it off. I gutted it and put it back on. Runs fine and even passed the smog test. Thank-you for everyone's help.

Holy crap!

Is that the inside of a cat or the remnants of a concrete block?!

That was the inside of my cat before I banged it around. It's no wonder the engine couldn't breathe!

Learn something every day...I was under the impression that GM used the 'ball bearing granuals' instead of honeycomb. Ive done a lot of mine on Fords and Mopars by just driving a tire iron thru the guts and hitting it on the sides. Ive never replaced a cat.

well, the entire exhaust system is easy enough to drop

and, the muffler is easy enough to check: knock on it. hollow? or no?

more effort has been put into this thread than the whole job would have taken.

drop the cat-back exhaust
you may be able to pour the entire contents out thru the down pipe, with no cutting, or seperating, re-install, and be on your way.

a new downpipe is a fine option

and - as you stated - the stainless exhaust is plenty fine. just shake out the junk - it'll fall thru.

[This message has been edited by Pyrthian (edited 02-02-2009).]

quote Originally posted by rogergarrison: Learn something every day...I was under the impression that GM used the 'ball bearing granuals' instead of honeycomb.

Roger, it wasn't the original cat.