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Discussion Starter · #1 ·
So another trip to the local Saab mechanic yielded a laundry list of big ticket items. I have been getting terrible gas mileage for quite a while. He tried cleaning the throttle body a while back, and it has a rough idle which was diagnosed as a faulty sensor in the (now clean) throttle body.. Haven't tackled that one yet..

But the most recent diagnosis is the poor gas mileage is caused by high back pressure from my exhaust system. My mechanical said the car feels slugglish off the line, so he looked into it and thinks that the catalytic converter overheated at some point and melted the internals, causing the current problem.

Any thoughts on this? Have you heard of something like this?

Another thing I'm wondering is how to go about fixing it. I'm in CA so apparently there's some new law that cats have to have a special code stamped on them, which makes aftermarket parts unusable (at least at his shop). Is there something I can replace it with myself that CA doesn't need to find out about? He also told me the whole exhaust system is a little rusty and his quote included 2 new mufflers as well. I'd like to avoid this if need be, but I also want my baby running fresh and clean.

Thanks!
 

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Cat's can take really high temps and repeated abuse-I doubt you "melted" it. It's possible it collapsed or got clogged. Get under the car and whack it-if it rattles then it collapsed/broke apart.
Have the mechanic drill a small hole before the cat and mount a pressure gauge-should not read more than 2-3lbs psi. Feeling "slow" off the line may be an inherent aspect of a turbo saab.
-Cm
 

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Exhaust external rust means little to nothing.
I'd contact your CA motor vehicle department and inquire about the catalytic converters, there could be misunderstandings here.
Find a honest shop, I'd be suspicious of this one.
 

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Discussion Starter · #5 ·
So I called the guy after cm's response and he said he did measure the pressure where both O2 sensors are, and it is indeed blockage in the cat. I've worked with him a little while and think I do trust him. I'm just looking for some reassurance..

My next question is how do I fix it? It's my understanding, to do it OEM, I need to replace the whole header pipe/cat combo piece (part# 5325501 on thesaabsite) for $1070+s/h. I can do this myself because it's all bolt-on. I can't do any welding, so to cut the cat off and replace with an aftermarket from Magnaflow isn't something I'll be able to do myself. Am I understanding that correctly?
 

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Discussion Starter · #7 ·
thanks saabkid. that's some good advice, as i'm DEFINITELY trying to save some money on this one. if i buy an aftermarket, CA approved cat, I could bring it somewhere and what do they do? Cut the existing cat off and weld a new one to the header pipe.. but what about where it connects to the flex pipe? i think that's a bolted connection now, and how do i make it continue to be? i'd go look at the car myself but it's still at the mechanic..
 

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What's the deal with CA-approved vs non-CA-approved cats? Should one avoid the non-CA-approved cats if they want to reliably pass emissions if they will never be in CA?
I would say about 200 bucks is the difference. I needed a cat on my old spg and went down to a muffler shop which tried to sell me one for 300 plus. Went home, bought a magnaflow, installed it and passed smog.
 

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Rather than a melted cat conv caused bad gas mileage, I think it is the other way around. Too much unburned hydrocarbons in the exhaust are burnt in the cat conv., causing the cat coated beads in the cc to overheat and fuse together. So whatever caused the bad gas mileage also ruined the cat converter. Unless you correct the cause of the bad gas mileage you could melt the new cat converter as well.
You should have gotten a check engine light from the O2 sensor readings. Also, some Saabs have temp sensor mounted near the cc to warn if the cc is overheating. Your fuel system has been feeding an excess of fuel to the engine.
As a hunch, I would replace the 'faulty sensor in the now clean throttle body'.
 

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Discussion Starter · #12 ·
California just likes to be different and make regulations more stringent. (Honestly, as a state with such a huge budget deficit, you'd think they could save a ton of money by just using federal regulations instead of creating departments that just come up with more stringent codes - but that's for another forum that i don't want to be a part of).

Anyway, from CA Air Resources Board web page

The Air Resources Board's (ARB) California Evaluation Procedures for New Aftermarket Non-Original Equipment Catalytic Converters (California Procedures) were adopted by the Board on August 19, 1988. An interim procedure, Optional Evaluation Procedures for New Aftermarket Non-Original Equipment Catalytic Converters, was set up to address requirements specific to catalytic converters for vehicles equipped with on-board diagnostics II (OBD II) systems and went into effect on December 2001. These regulations require new aftermarket catalytic converters to comply with requirements of Title 13, California Code of Regulations (CCR) section 2222(h) in order to be exempted from California's anti-tampering law (Vehicle Code section 27156), thereby allowing them to be offered for sale, sold, installed or used in California.

The ARB adopted revised regulations and evaluation procedures in October 2007 for the approval of new aftermarket catalytic converters sold in California. The requirements apply to all new aftermarket converters produced for sale or sold in California after January 1, 2009. The requirements also sunset provisions allowing the sale of certified used catalytic converters beginning July 10, 2008. This means that no used converter can be legally advertised for sale, sold, or installed in California after this date.
 

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Do you have a CEL? If the cat is gone then the downstream O2 sensor will follow the upstream sensor and you will get a CEL. You could use OBDII reader to watch the waveforms from the two O2 sensors to see if this is the case.
 

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Discussion Starter · #14 · (Edited)
john - valid point. i've forwarded the question on, so we'll see what my mechanic thinks. he told me a while ago there's a sensor in the throttle body that goes a little crazy at certain times, which causes a rough spot in the idle occassionally. with the computer hooked up, he watched the sensor reading jump at the same time the idle choked (it drops a little and the car shakes). same thing happens 90% of the time starting cold. do you think that could be the bad gas mileage culprit?

gnode - not sure what a CEL is. Could you elaborate? -edit: No check engine light..

thanks for all the input!
 

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http://www.aa1car.com/library/converter.htm
This is helpful for all. 2000 degrees F to begin to degrade the catalyst-to begin. If you actually "melted" the thing, it would be so hot it would burn the insulation/rust proofing under the car and you'd smell it. You probably plugged it with carbon, which would explain your crappy mpg. I work closely with one of the scientists who developed the cat and have grilled her about them-they should never fail.
-Cm
 

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you believe everything you read? or speak from experience?

cats fail end of story. you say 2000 degrees begins to melt the cat, well a saab 2.3L will run in the 1000-1200 degrees celsius aka 1800-2200 farenheit. sounds like enough to melt a cat doesnt it?

and those temps are on a well running motor, expect higher if a maf is dying or something else to cause to it lean out.
 

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http://www.aa1car.com/library/converter.htm
This is helpful for all. 2000 degrees F to begin to degrade the catalyst-to begin. If you actually "melted" the thing, it would be so hot it would burn the insulation/rust proofing under the car and you'd smell it. You probably plugged it with carbon, which would explain your crappy mpg. I work closely with one of the scientists who developed the cat and have grilled her about them-they should never fail.
-Cm
The report linked in the above post is an excellent explanation and I recommend it. Read it yourself and draw your own conclusions.
 

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Discussion Starter · #18 ·
Update

Alright, so here's the update on my unfortunate situation...

After the suggestions from this thread, I called a few local muffler shops that had good reviews online. Both told me that there were no aftermarket cats approved for the 2002 9-3 in California (stupid state). Apparently each aftermarket mfgr needs to have their cat approved for each specific model. They have them for 2000, 2001, but not 2002. You can find websites that claim they are legit, but they are not.

I said screw it, I'll get the Magnaflow cat intalled that's approved for the 2001. Went to a shop that quoted me $300 installed (matched the other quote I got). When I got there the guy said "which cat?" I didn't know there were two! There's one right where the downpipe comes off the turbo, and one after the elbow back under the car. He said he couldn't do the top one but could do the bottom. I called my saab mechanic that diagnosed the problem and his measurement was from the O2 sensors around the top cat.

What do I do now? The saabsite has an OEM replacement for $1100. i assume this is approved in CA since it is OEM. There are also aftermarket cats on autopartswarehouse for $3xx but I don't know about the quality and not sure if the illegitimate aftermarket cat will get picked up in 2 years at my next smog test.

Any suggestions on aftermarket cats that are direct bolt on replacements? They should include downpipe & both cats.

Anybody have experience with CA smog tests and aftermarket cats? How would though know it was aftermarket if I install it myself?
 

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As a general statement: Anytime you need to replace a cat converter,before you replace it find and fix the condition that caused the cat to fail. Do this before you install the new cat. Otherwise, you are likely to ruin the new cat converter. Your best option would be remove whichever converter you think is bad, or both. Install a straight thru pipe or pipes. Now with the straight thru pipe(s) in place of the converter(s) Do you still have poor gas mileage or any other sign of trouble in the engine or the engine management system? Does a known good O2 sensor in the exhaust pipe near the manifold show that thefuel/air mixture being fed to the cylinders is correct?? If the mixture is correct the O2 sensor, after is hot should output a voltage that constantly varies between about .1v and .9v, and fluctuates up and down above and below .45v.
If you can't do the straight pipes test at least check the voltage output of a known good O2 sensor in the exhaust pipe.
 
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