Diagnosis: Failed and blocked cat

[silversync]

A couple of months ago the Vanagon (Syncro) was driving very poorly. There was no power, almost like dragging a brake or some heavy trailer. The engine made lots of noise and revs, funky sounds, but can't go fast.

I took it to a shop and they diagnosed a failed and blocked catalytic converter. He said they measured 2 lbs back pressure; don't have much experience with that test but evidently that was conclusive. I assume that is measured through the O-Sensor hole?

The current state is the O2 sensor is removed, and it now makes power like before, but of course is noisy and smelly. The advice was to wait until next summer when the CA smog test is due, then get a new cat, O2 sensor, and set it up properly. It seems like it is running super rich, and gas mileage is probably way down. Not big problem, no trips planned, just around town utility uses.

I seem to remember installing the Cat around maybe 16-17 years ago. Does anyone know Cat failure rates? New CA Cat is showing $1,445.80 at Van Cafe (OMG). It will take some meditating to face that expense.
_________________
Roland: '89 Syncro, '02 911 C4S, '10 Audi A4 Avant

[crazyvwvanman]

If they didn't open up the exhaust then they are likely making an
educated guess.
Pieces of the cat can break off and go into the muffler, partially blocking it.
In that case it isn't just that the cat is blocked, and replacing the cat might not do the full job without also getting the pieces out of the muffler.
It is also possible to have damage/blockage on the upstream area of the cat without any broken pieces passing through to the muffler.

In your situation I would remove the cat and look in both ends to see what is going on.
If justified bust the remains out of the cat, install it with a NEW O2 sensor and see how it runs.
If all now ok replace the cat now or when the right time comes.
If not running ok, don't ruin a new cat before the cause is remedied.

Mark

[dobryan]

Here is what mine did. Drop your muffler and look.

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Dave O
'87 Westy w/ 2010 Subaru EJ25 (Vanaru) and Peloquin TBD

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[DanHoug]

[E1]

Sending you down the road with essentially a big exhaust leak is not confidence-inspiring. They at least should have reinstalled the O2, even if unwired.

Was the cat getting blazing hot while running poorly?

Did they take temperatures?

I don’t know what back pressure should be, but presume it’d be really low if running poorly — with a good cat or not. Meaning, I can’t help but to wonder if their diagnosis is exactly backwards.

When we had a cat go bad, if anything it was very quiet, not loud or having funky sounds, and as the best description it ran like it was constipated… or, Ahem, ran like it had 20 horsepower.
_________________
If ever twice as rich, we’re gettin’ a double-wide
’84 “Westfailure”/2.1 Digijet/5.43 Ring & Pinion/Peloquin/D-rated BFG KO2s

AI has spoken to further illiteracy, to steal, to cheat, and to replace humans
The caveman’s first question to the headhunter: “Hey, you got any coffee?”

[DanHoug]

i missed the part where they left the bung open... that's just wrong as it can be a fire hazard for your van. and of course all the funky noises are gone because you can't hear them anymore over the hole roar.

thread a new O2 sensor in the hole and connect it. you may find that it runs and drives well after that. you need one regardless if you replace the cat or not so no money lost. shop probably didn't send the old one with you.
_________________
-dan
60% of what you find on the internet is wrong, including this post.

'87 Westy & '89 Westy both 2.1 4spd

Past projects can be found at--
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[crazyvwvanman]

My dead cat photo from an old thread.

[zerotofifty]

Besure to install a NEW O2 sensor with your NEW catalyst. A weak or what is known as a lazy O2 sensor (one that reacts slowly) will not give the most optimal mixture, and having a less than optimal mixture may harm your NEW and very expensive catalyst. Going forth, replace your O2 sensor on a regular basis in order to achieve longest catalyst life. A bad O2 sender can kill a good catalyst.

What others said about chunks of catalysts blocking the muffler is correct, so check the muffler too. If the catalyst has indeed failed and is falling apart, then replace it or hollow it out and inspect the muffler for blockage too.

Note a failing catalyst that causes a minor clog may continue to break up, and cause further clogs, thus in the interest of not becoming stranded do to a total blockage, it is good to remove the catalyst and either gut it out, or install a new good one. If new catalyst installed, get a new O2 sensor too unluss you know your current one is fresh and not "lazy" The O2 sensor is only a bout 1/10th the price of the catalyst, dont be penny wise and pound foolish with the O2 sensor and catalyst.

PS when you do get a new catalyst, hold on to the old broken one, bust out its guts so it flows clear, then keep it as an emergency part incase your new catalyst gets stolen, at least you will have a temporary fix until the stolen unit is replaced.

Good Luck!!!!
_________________
Sorry About That Chief.

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Words to live by.

[zerotofifty]

[kamzcab86]

I put a vacuum gauge on the intake earlier this year, which indicated a potential restriction in my 2.1. Removed the O2 sensor, which was fouled. Removed the cat converter... restricted without visible physical damage:

Instead of going to the hassle of destroying ^that, I simply installed a straight pipe and new O2 sensor until emissions time (which, fortunately, doesn't require the expensive CA cat).


Considering the OP's O2 sensor was left removed, I would guess that the back pressure test was performed at the O2 sensor bung. From what I've read, back pressure should not exceed 1.25 PSI at 2500 RPM.
_________________
1986 Cabriolet: www.Cabby-Info.com
1990 Vanagon Westfalia: Old Blue's Blog
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"Real knowledge is to know the extent of one's ignorance." - 孔子

[do.dah]

I would just love if somebody with a blocked cat, would try one of the 'spray into o2 bung' cat cleaners, to see if the stuff actually does work? Ya know, in the name of science?

[Abscate]

[do.dah]

So, you've tried it? Or, are you just being a squak box and repeating what someone told someone that knew someone' bother-in-law' father?
Or, you'd rather spend hundreds of $ on a new part, rather than a few $'s trying a 'fix' that may or may not work?

Conventional 'wisdom' says they don't work. Without having actually tried it.
Scientific wisdom, tries it several times and tries to qualify a statement.


Pulling and replacing a cat on a vanagon, ain't that hard.
If the cat is intact, why not try a commercial 'spray in' cat cleaner? Worst that can happen is ya spent a few $'s and a little bit 'O' time removing it and replacing it......

[Abscate]

[E1]

Cats indeed plug up if running rich for too long. Fuel burns off but not entirely, and gas is a product of oil after all.

I’ve read very good things about Cataclean and would try it in a minute if:
— The cat was overheating
(meaning outlet temps are at least 200F above inlet)
— Visual inspection showed it to be intact

I well recall a banned poster here claiming NO additives worked, which included fuel injector cleaners, oil stop leaks, fuel driers, Blah Blah Blah.

Entire industries are rarely if ever built upon nothing, and blowing others’ money on possibly-unnecessary parts replacement isn’t helpful here.
_________________
If ever twice as rich, we’re gettin’ a double-wide
’84 “Westfailure”/2.1 Digijet/5.43 Ring & Pinion/Peloquin/D-rated BFG KO2s

AI has spoken to further illiteracy, to steal, to cheat, and to replace humans
The caveman’s first question to the headhunter: “Hey, you got any coffee?”

[kamzcab86]

[silversync]

Thanks all for the comments, useful for figuring out where to go from here.

[E1]

Any good businessman should never take offense to questions like that.

Rather, they know their work is good, they know they’re honest and not everyone is, and they understand reputations are built on it.

In my hand-painted pinstriping and lettering days, I routinely got asked “Will this come off in a car wash?” I knew others stripers over-thinned their paint to pull longer lines, and it often came off or faded within a few years.

I learned by 19 that the best way to avoid fielding questions was to address these things without being asked. Sadly, the days of vendors acting like this have faded dramatically, but the good news is the best ones present themselves as such pretty quickly — if customers know what to look for.
_________________
If ever twice as rich, we’re gettin’ a double-wide
’84 “Westfailure”/2.1 Digijet/5.43 Ring & Pinion/Peloquin/D-rated BFG KO2s

AI has spoken to further illiteracy, to steal, to cheat, and to replace humans
The caveman’s first question to the headhunter: “Hey, you got any coffee?”