Coming home with a Buickload

[Captainclock]

Originally Posted by MadMan

Ok, Captainclock. There are all sorts of things wrong with what you are saying here. *sigh*



A downstream oxygen sensor will not (on most vehicles) mess with fuel economy, or how the engine runs. The downstream sensor exists only to monitor the performance of the catalytic converter. The upstream oxygen sensor, however, exists to monitor the fuel/air ratio at which the engine is running, giving the input to the computer so it can adjust how much fuel it injects, and also to provide a baseline for the calculation of converter efficiency, which then also uses input from the downstream sensor.

Also, it is not 'part of' the converter assembly. It's probably just rusted stuck in the bung, and that mechanic you talked to recommended just changing the whole shebang to make things easier for everyone. I would recommend the same thing.



Because it's a regulation for cars sold in the USA. Any car must be capable of going 200 miles on a tank of gas. But you do realize that maybe different cars get different gas mileage? And have different sizes of fuel tanks? That's why it's a guideline, not an immuteable law.



Exactly. There's your problem. You haven't talked to a real mechanic about the subject. You are now. That one guy you talked to, well, I would recommend the same thing he did, but I would additionally advise you as I am now, about this predicament, to get you completely informed about the matter at hand before you start throwing money at it. Because, if all you say is correct, you're gonna replace that converter and sensor, and the car won't run any better, or improve the fuel economy, and you're gonna think that mechanic did something wrong, when in reality, you're just not fully informed of the situation. Read what I said again:



You have a converter efficiency problem (or so I gather). But you also have, with it, a fuel economy problem. Likely, what is actually happening here (as I've been trying to explain) is that because the engine is running poorly, too rich most likely (using too much gas), the catalytic converter will not be able to keep up, thus giving you a code for converter efficiency. Which, btw, I'm only guessing that's the code you had, because you never actually said, only implied. In many scenarios, the engine computer will not really 'know' that the engine is running too rich or not firing right or what have you, it simply thinks it is making the appropriate corrections, and for some reason the catalytic converter isn't doing its job. When in reality, this might not be the case at all.




Facehoof.

O_o That's just... I don't even. Your car is not a lawnmower. It's also not British, a tractor, or made before 1960. It's not supposed to leak oil -or- burn it. If it's overfilled, it will usually just burn the oil out, like a lawnmower, (which will damage the converter, btw). But you say it's leaking out of the valve cover onto the exhaust manifold. Which, though not terribly common on American cars, if it's bad enough, can leak vacuum as well, and make the engine run poorly.

There are all sorts of possible causes why your mpg's might be down. Converter efficiency and/or downstream O2 sensor? Not generally among those causes. 'sall I'm saying.

OK, well then I guess that I will need to replace the valve cover gasket then because that's what the mechanic said the engine was doing (and in fact that same thing happened to my Chrysler Cirrus I had before except instead of the oil leaking onto the exhaust manifold like my Buick is it leaked into the spark plug chambers. And I'm guessing that according to what you were just saying that the engine being filled too full of oil is probably why I'm having issues with my Catalytic converter, although if that's the case I wonder why the mechanic didn't notice that... because I knew the engine was too full of oil but I didn't say anything to the mechanic about it because I thought they would of noticed that themselves, but apparently they didn't.