Question about 1999 Toyota Corolla

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Catalytic converter error code

Hi,

I have a 99 toyota corolla with 147,000 miles on it. The Check engine light of my car keeps coming on intermittently. I got the code checked and it says catalytic converter below threshold. Usually the light goes away by itself in a day or two, however that didn't happen the last time it came on,which was 6 weeks back. I took my car to the dealership hoping they would tell me exactly what's wrong i.e. whether it's the sensor (front or back) or it's the converter. Well, that didn't happen and the dealership advised that I get the exhaust pipe, catalytic converter and both the sensors replaced for a price tag of $2,500. At the time they erased the code and the light was gone, however it's back now and I am looking for a good solution. My car is in a good running condition...gave me about 38 mpg in summer, unfortunately it's down to 33 mpg right now and I am not sure if it's the cold whether that's responsible for lower mileage.

Please advise on how to find out if the sensor is bad or if it's the converter. Also, is it normal for corolla to give lower MPG in winter?

Thanks for your advise.

MP

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the dealership advised that I get the exhaust pipe, catalytic converter and both the sensors replaced for a price tag of $2,500.
Very pricey - you don't know if the sensors are bad until the cat is replaced and the two sensors are not part of the cat; one is located near the exhaust manifold, the other after the cat.  I would check with independents for their prices on replacement of the converter alone, then replace the sensors if they still are producing an error; they are exposed to very high temps for a very long time so they may truly be bad. The cost for a generic catalytic converter is under <$100 US but those do have to be installed by pro's since they need to cut and weld to use a generic. There may be an aftermarket unit that won't require that; do a little research on it. Actually, the 147K is impressive; the feds only require that emissions systems (oe any part of it) last 50K so you have been getting a free ride.
Also, your reduced gas mileage can very well be caused by the decay of the cat. If the guts start to disintegrate, they can migrate into the muffler, partially clogging it and creating higher back-pressure than the engine likes. On a past car of mine, my mileage increased by about 20% over a few thousand miles, then started falling again and the car very noticeably lost power until it wouldn't pull a grade on my daily circuit any more. After investigating and listening to the tailpipe, I determined that the muffler was blocked; the exhaust 'note' was no longer a muffled firing noise but a steady hiss (you should listen to yours at an idle), indicating that the exhaust was struggling to exit. That particular car had a heavy gauge stainless exhaust system so I took my .44 magnum and shot twice into the nearly straight system, punctured nothing to the outside world but permanently cleared the muffler of obstructions. I don't advise doing that with the average exhaust system. BTW, the exhaust note was only slightly louder than it had been when new.    

Posted on Oct 30, 2008

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