anony91xj said:
O2 sensors are not a regular maintenance item. They should only be changed when they go bad, not just because they're old. My Grand Prix has 213,000 miles and the original O2 sensors, they still work fine.
Dude, he's got a 1997 with OBDII. Forget your "I hate self-diagnosing systems" attitude in modern times, especially with any vehicle made after 1996 (points and condensers are dead, move on...seriously). He can monitor everything with a shop scan tool, and if the O2 sensor(s) are out of spec, that will tell him. You are incorrect, a factory O2 sensor can tell how rich or how lean, it just doesn't have as wide a spectrum as a wideband O2 sensor...a factory O2 is confined to a much smaller voltage range. Unless you've got a turbocharged car or other performance application that requires VERY specific A/F readings, a wideband is pretty much unnecessary, that's why OEM's have not switched to them. Wideband sensors are expensive and not necessary in 99.9% of factory applications.
If the scanner shows all the O2 sensors reading within spec, there is NO REASON whatsoever to replace them and he'd be just wasting his money. Besides, if any of his O2 sensors were far enough out of spec to cause a problem, his Check Engine light would be on.
Seriously, I work in the modern auto repair industry. With OBDII, the best diagnostic tool a mechanic can have is a good scanner. Sure, DVOM's are still necessary, but in many instances, a Snap-On or OTC scanner makes diagnosis MUCH easier, a DVOM can often help confirm the diagnosis, or determine the difference between a sensor problem and wiring problem. Try working with a proper shop scanner and OBD vehicles, and your attitude towards them will change, I guarauntee it.
I didn't say they HAD to be replaced at 80K - and I gave a couple examples of why not - I just said they SHOULD be replaced at 80K. It's what's recommended, not required.
Also, if you've read what I've written for any length of time, you'd understand that, in my mind, progress just for its own sake isn't usually. Sorry, but I've been doing this long enough to know that newer just ain't always better, and I've long believed that "technology should not replace skill." Besides, I know I've run across a few cases where OBD was wrong, and I was right - but try convincing anyone else of that. Besides, any system that makes it more difficult to actually IMPROVE things should be scrapped - there's nothing designed by the mind of man that can't be improved by the mind of man. That's my story and I'm stickin' to it. I prefer systems that are adaptable and NOT hidebound - which is why I prefer RENIX over OBD. That's not to say that I can't WORK on OBD when I have to - but I'd prefer not to own it.
I'm not going to come out and say that points/condenser and a carburettor is going to be better - it's not. But, let's stop overhauling things just for its own sake - and it should also be borne in mind that legislation cannot effectively drive innovation and useful improvements, no matter WHAT Congress things (and the EPA, and ...
ad mauseum. Legislators and rulemakers, like lawyers and accountants, simply have NOTHING useful to contribute to engineering, and they just don't realise it.)
And, WHEGO sensors are starting to be used in some applications - most of the literature I've found of a technical nature is put out by Toyota training - which, likely, means it's OEM. This is a case of something "new" that is also "useful" - it's like anything else with a number, it's useless if it can't be quantified properly.
And, as far as the "I hate self-diagnosing systems," it's probably because I came up using systems where I actually had to do the troubleshooting and "grey matter" work on my own, and I don't see any reason to stop doing so. Pardon me for saying so, but it almost takes a combination between an idiot and a EET major to work on vehicles these days, and I am neither. And, of course, with the strictures laid down by OBD-II these days, it's damn near impossible to modify things to make them run BETTER, and some systems on OBD are needlessly complex - and can probably be replaced with "technology" devised 50 years ago, and be more reliable and more effective to boot!
And, I
have worked with a "proper shop scanner" (Snap-On MT2500 with "all the fruit," in fact,) and OBD vehicles. The problem there is that the tools needed to work on OBD are gradually getting out of reach of the hobbyist, which is also a great mistake. I don't care for ANYTHING that isn't field serviceable, diagnosible with a minimum amount of equipment (sometimes knowledge is enough,) and that you can't improvise a repair on until you get back to civilisation to fix it properly. I know that OBD has a "Limp Home" mode programmed into it, but it just KILLS performance and efficiency, which tells me that it's not programmed well. An improvised repair isn't going to be as good as a proper repair, but it should be pretty damn close, if you know what you're about.
As far as NHEGO vice WHEGO, the NHEGO may be able to tell you "how" rich or lean, but from what I've seen of the voltage output curve, it's a VERY narrow range, and that gives the signal little utility. It falls off the scale rapidly outside the range of, as I recall, 12.5:1 to 16:1AFR (ish,) and it spends a lot of time "bouncing" trying to get back into that range. WHEGO sensors will give you an accurate and useful reading from, say, 4:1 to about 25:1AFR, which becomes a lot more useful to someone who properly designs a feedback system. In fact, using WHEGO sensors could probably obviate a number of other systems, if they'd think to apply them properly (lowering TCO and aggregate system production costs.)
Sorry, but I'm not buying it. I'll grant that OBD would be more useful if unqualified individuals and organisations would stay out of the design process (I've very rarely met a lawmaker or a regulation writer that actually KNEW ANYTHING about the subject matter at hand at the moment!) but until that happens, I don't see anything to like about OBD-I, OBD-II, or the proposed OBD-III.
That's my story and I'm stickin' to it!
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