2001 Forester Catylitic Converter or Blown Engine?

[kfabel]

My 2001 forester has 90k miles on it. . easy, highway miles. The car runs great. The check engine light has come on and off now for the past 2 years. In as much as the car was running great . . i paid little attention to it. In the past 3 months the car appears to be using more oil than normal. I took it to my mechanic (not a subaru dealer) to check it out. The check engine light indicates that there is a problem with the catylitic converter. There is a small amount of black on the tailpipe. My mechanic . . admiting that it is difficult to diagnose, told me this could be signs of bad valve seats or piston rings. . . or . . if the oil consupmtion is less than a quart per 1500 miles . . a bad converter.

 

i did some research on line and there appears to be a known problem with the catylitic converter and the O2 sensors for this car . . .

 

is this engine really going bad? or is it just a converter problem? any thoughts???

[The Dude]

PROPERLY maintained, the 2.5L SOHC powerplant should have a long life expectancy. So, if you haven't ignored oil changes, like you have the CEL light, you should be OK. First question, what code are you pulling? The CEL is on, so there should be a code. A little black on the exhaust pipe is normal. The upstream O2 sensor frequently fails right around your mileage. That is where I would look first. Unless, for some reason, you just want a new engine.

[kfabel]

Mobil One every 6k-7k miles so oil maintainence is not the problem.. . not sure of the exacte code . . my mechanic said 'bad catylitic converter' thanks for the advice

[The Dude]

Mobil One every 6k-7k miles so oil maintainence is not the problem.. . not sure of the exacte code . . my mechanic said 'bad catylitic converter' thanks for the advice

 

 

Your mechanic is probably an OK guy, but this is giving me a queasy feeling. INSIST on knowing the exact code he pulled off your car, and then you look up the description for the code. The "condition" of the cat is monitored by both an upstream and a downstream oxygen sensor. There is no cat sensor, per se. Unless something abnormal has happened, your cat should be fine. Probably a failing oxygen sensor is leading the mechanic to believe your cat is bad. FYI, an oxygen sensor is actually a primary battery, one that runs on oxygen. The more oxygen, the higher the voltage from the battery. But just like any primary battery in flashlight, it eventually wears out. Yours is about due. Usually only the upstream sensor needs to be replaced.

[slo5oh]

If your O2 sensor has been failing for sometime you could have burned out the cat. Too rich or too lean for an extended period of time will cause your cat to fail. You'll know real quick if you try to smog it. Too lean will burn it out and your HC (hydrocarbons) will be way high. Too rich and you will "plug" the cat and you'll lose power. My father has a Dodge truck with a 360 that he bought with a bad cat. Those trucks run rich so it plugged it. Luckily it was under the 7 or 8 years manufacturers are forced to give on cats so the dealer put a new one on. I was there when my father drove home with a huge grin on his face and ripped the tires loose in the driveway... like a kid in a candy store. He said it was making gobs more HP after the new cat.

[kfabel]

If your O2 sensor has been failing for sometime you could have burned out the cat. Too rich or too lean for an extended period of time will cause your cat to fail. You'll know real quick if you try to smog it. Too lean will burn it out and your HC (hydrocarbons) will be way high. Too rich and you will "plug" the cat and you'll lose power. My father has a Dodge truck with a 360 that he bought with a bad cat. Those trucks run rich so it plugged it. Luckily it was under the 7 or 8 years manufacturers are forced to give on cats so the dealer put a new one on. I was there when my father drove home with a huge grin on his face and ripped the tires loose in the driveway... like a kid in a candy store. He said it was making gobs more HP after the new cat.

 

 

forgive my ignorance . . what do you mean by "smog it" how is that done?

[The Dude]

Actually, the 2.5L engine will run along very nicely without the oxygen sensor. Under normal conditions, even with a failed oxygen sensor, it should be very unlikely that the cat has been damaged. I'll guess that "smog it" means to have the car tested for tailpipe emissions. Personally, I would repace the upstream oxygen sensor before I did anything else. If it has not actually failed, it is very near to the end of it's life. You really have very little to lose. I think a new oxygen sensor is about $90. A new cat is a whole lot more.