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Location: Cambridge, MA
Posts: 44,281
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Clogged Catalytic Converter
if the nuts were old and rusty on the O2 sensor studs just ahead of the cat, would a plugged/clogged cat "blow them off?"
Happened just after I got my 94 4Runner up and running. Put new nuts on, it's fine. Getting horrible gas mileage on the highway, 10MPG, also can smell something like propane turning off the truck and getting out. Are these symptoms the cat needs replacement?
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Tru6 Restoration & Design |
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12-14-2010, 10:08 AM
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Get off my lawn!
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When the cat plugged up on my El Camino it just felt like I was pulling a big trailer.
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Glen 49 Year member of the Porsche Club of America 1985 911 Carrera; 2017 Macan 1986 El Camino with Fuel Injected 350 Crate Engine My Motto: I will never be too old to have a happy childhood! |
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12-14-2010, 11:30 AM
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For what it's worth......my 03 Tacoma did the same thing.
I could hear an exhaust leak and after some investigation discovered my rear O2 sensor just laying on the studs....no nuts. How they came off i have no idea. I rethreaded the studs (ASE) and put new nuts on it. My cat. is fine by the way. P.S. my 95 4 runner exhaust always smelled like rotten eggs.
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Pete 79 911SC RoW "Tornadoes come out of frikkin nowhere. One minute everything is all sunshine and puppies the next thing you know you've got flying cows".- Stomachmonkey |
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12-14-2010, 11:57 AM
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You do not have permissi
Join Date: Aug 2001
Location: midwest
Posts: 39,832
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You can quasi-check the cat efficiency by checking with an infrared thermometer before and after the cat. After warmup, it should be 50-100deg hotter after the cat which show the molecules are getting burned up inside.
Try taking out the O2 sensor and see if it drives better. The O2 is only used after the engine is warm and in closed-loop. I once started getting terrrible performance from a daily driver until the rusted 2 y.o. Midas muffler fell off. Ran good after that. |
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12-14-2010, 04:13 PM
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Banned
Join Date: Mar 2007
Location: Ft.Lauderdale, FLORIDA
Posts: 2,813
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My 928 ran rich for years and DESTROYED one side of the 928S4 cat that I installed on my car....at a cost of $500! It is plugged, the ceramic matrix melted and caused a blockage.
I want to put a pair of Random-tech cats on my car, since they cause almost no back pressure...and my rich-running condition is finally solved, but they are $500 each... N! |
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12-14-2010, 04:20 PM
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Location: Cambridge, MA
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all good to know, thanks. A friend also said the cat glows hot when plugged up.
So I don't think I have a bad cat. THis engine is the worst Toyota ever made, so it comes sluggish fresh off the showroom floor. I think it's operating nearly as well as my old 95 did. So what else could cause 10MPG on the highway? Truck is rated for 16, my old truck (gutted of 200 lbs) got 17-18.
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12-15-2010, 07:22 AM
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Have you checked the cap, rotor,plugs and air filter lately?
A new fuel filter might help too. Is this a 4 banger or a V6?
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Pete 79 911SC RoW "Tornadoes come out of frikkin nowhere. One minute everything is all sunshine and puppies the next thing you know you've got flying cows".- Stomachmonkey |
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12-15-2010, 08:37 AM
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Location: Tornado alley
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If a cat is plugged, then it is unlikely that it will glow. the glowing is caused by it working, i.e. oxidizing (burning) the CO and unburned Hydrocarbons. Many will heat up enough to glow a little even in normal operation, but if your engine is dumping fuel, then it might overheat enough to really glow...
If it is plugged, it will increase the back pressure and cause the engine to run sluggish.
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Jack '70 914/6 |
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12-15-2010, 08:41 AM
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Air filter looks pretty good, checked that on Saturday. I do need to check all those items. It's a V6, new motor and was installed for $5K back in 2007.
something of interest: when removing the gas cap to fill-up, it's pressurized. My 95 didn't do that, but then it had a gas tank leak at the top. Also, I found what looked like silver antiseize or grey grease, a thin film, all inside the throttle body. I had removed the large rubber boot that goes from the air filter to the TB to reroute an accelerator cable. Noticed it then, just did a quick clean out with a rag, it's been very cold outside.
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12-15-2010, 08:44 AM
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Information Junky
Join Date: Mar 2001
Location: an island, upper left coast, USA
Posts: 73,189
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Shaun, what can happen is, the ceramic center starts new with the aspect ratio of a soup can. It slowly breaks-down until it has the aspect ratio of a tuna can. ..at which point it can flip sideways, and almost completely block the cat exit to the tailpipe.
I had this happen once. So, I took the cat off, set it in a garbage can, and rammed a crowbar down the center, to brreak-up what was left of the ceramic. (re-installed - ran great)
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Everyone you meet knows something you don't. - - - and a whole bunch of crap that is wrong. Disclaimer: the above was 2¢ worth. More information is available as my professional opinion, which is provided for an exorbitant fee. 
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12-15-2010, 08:47 AM
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Good idea, thanks Glen.
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12-15-2010, 08:49 AM
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Senior Member
Join Date: Feb 2000
Location: Lacey, WA. USA
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Quote:
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Man of Carbon Fiber (stronger than steel) Mocha 1978 911SC. "Coco" |
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12-15-2010, 09:50 AM
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Carrera
1979 Porsche 911SC
