diymarc

I've been over just about every emissions control device in my '88 hatchback (4 cyl, carb), except for the catalytic converter, and they all seem within spec. Even the O2 sensor seems okay, but all I've got is a cheapy VOM to do that check. Both are original equipment, with 150K miles. Maybe their performance has degraded. I'm failing the NOx part of a emissions test. EGR seems okay.

- How long do O2 sensors & catalytic converters last?

- Are there some relatively simple tests I can perform to confirm their operation?

After finding some vacuum leaks and doing a few other tune up items - wow! I'm not a power/speed freak but I can sure feel somethink kick in when I floor it on the freeway.

Thanks,
Marc

RotaryBzzz

Cat convertors don't work to reduce NOx emmisons. Catalytic convertors work to change Hydrocarbons (HC) and Carbon Monoxide (CO) emissions into water (h20) and CO2 (using O2 in the process - the reason why you have that thing called a 'smog pump' - its just an O2 pumper). NOx emission are dealt with pre-convertor.

Have you noticed your oil is super black? That is usually a sign of higher-combustion temperatures and blocked egr passageways....not the egr valve itself but the passageways...

You might check http://www.deja.com and use the advanced search for "civic smog problems" in alt.autos or something like that. Do a mass search then get more specific.

Oh, and if you've maintained your car and are not burning any oil (consequently coating the convertor bed and o2 lambda crystal), i would doubt its your o2 sensor or cat going bad. If you smog check had low HC and low CO, your convertor/O2 sensor is good for sure...

An easy test to check the cat convertor is to put your hand in back of the exhaust and "feel" if any moisture is coming out. Do this after you've driven somewhere/ warmed up properly. Moisture is good...means h20 is being created. Then smell your hand. If your hand STINKS BAD...well...your convertor might just be getting worn out. STINKs little/medium...your still good. That's just for HC. CO and NOx are odorless however....


[Modified by RotaryBzzz, 12:38 PM 8/27/2002]

diymarc

Thanks for the site, I'll check it out.

I've applied vacuum to the EGR value at idle and the car died as it should. This indicates open passages. So I'm pretty sure I'm okay there.

About catalytic converters you are mistaken. Called 3-way converters they handle all 3 pollutants. Quoting from my '88 Accord service manual from Honda - "The 3 way catalytic converter is used to convert HC, CO, and NOx in the exhaust gas to CO2, N2, and H2O vapor." Clearly, even 14 years ago cat converters could reduce NOx. I think you need to do some reading on the topic.

O2 sensors can fail over time by indicating a false rich, or sometimes false lean. If false rich then the emission control system responds by leaning the A/F mix, making it too lean, which in turn drives HC & CO way down (plenty of O2 to oxidize them) and sets the stage for NOx production, at the same time preventing the cat converter from reducing NOx (it needs a slighly rich exhaust to do the reduction). So, in fact, low HC & CO can be an indication of a shot O2 sensor, which is contrary to your statement.

Regards,
Marc

GimpyAccord

its been my experience that O2's generally lose senstivity rather than flatout go bad... barring the car isnt REALLY old that is (and putting oil and heavy carbon on it). cleaning them out with a propane torch works wonders for them. I just put the tip inside the propane flame for a few seconds at a time until all contaminants get evaporated by the heat


far as your cat goes it could have deteriorated .. i actually replaced the EGR on a 1992 Saturn SL1 once thinking that was the problem when it was really a decayed cat... but that was causing serious drivability problems not emissions failures


[Modified by GimpyAccord, 6:20 AM 8/28/2002]