Hi Richard, On Wed, Feb 9, 2011 at 9:38 AM, Richard C. Wagner <[email protected]> wrote:
> Charlie: > > > I just failed the bi-annual California emissions test on my '89 L-Jet >> Spider for marginally high CO at 25mph. Here are the results: >> >> 2801 @15mph, Max CO Allowed 0.78%, Measured CO 0.78% PASS >> 2870 @25mph, Max CO Allowed 0.66%, Measured CO 0.78% FAIL >> >> The other tests (HC, NOx) passed and actually get better with speed, so >> the >> catalytic convertor is working. >> > > Have you done anything on the car since the last time it was tested? Does > it seem to otherwise be running just fine? > > Yes. The O2 sensor died between the 2009 test and the 2011 test. So it's brand new and putting out a variable signal. The engine runs fine at all speeds. It does smell a little rich after warm-up, but I'm not sure I trust my nose as a calibrated instrument. ;-( > They way the L-Jet system is designed, it should be correcting the mixture > if the O2 sensor is working correctly--even if some other factors are off. > Here are some things to consider: > In theory, yes. I suspect if the injectors are leaking, then the ECU might not be quick enough to keep up with the variations. That's why I was interested if anyone else had this problem - HC and NOx are OK, but CO is marginally high. > > - With a working O2 sensor and everything else in working order, if the > converter isn't working properly you'll still get measurable CO and HC > emissions. > Both NOx and HC are below the max. So it appears the cat is working. Maybe not like new, but it's doing something. > > - With the O2 sensor NOT working and everything else--including the > converter--in working order, you should see almost no CO or HC emissions. > With a solidly working converter, the mixture *can* be ever-so-slightly rich > and the car will still produce little CO or HC. > > I'd suggest putting in a new air filter, checking the O2 sensor and having > the converter checked. > Yes. I've put in a new air filter and spark plugs after failing the first time. I checked the new O2 sensor before I took it into the smog station the first time. I think I will tighten the AFM spring to lean things out a bit just for good measure. Ideally, I'd like to do things one at a time and see what the results are. But you only get one retry for the $60 fee. If you fail a second time, you start with another $60. So I'm looking for all the easy stuff to do before taking it in for the second test. > With the car warmed up and idling, disconnect the O2 sensor, place the > positive lead of a VOM on it, and the negative lead on a good ground. You > should see a varying signal around 0.5 volts. If the signal doesn't vary, > the sensor is shot. If the voltage is high (meaning the mixture is rich), > then there is either something wrong with the engine or the sensor is shot. > If it shows a low voltage but the engine isn't stumbling, the sensor is > shot. If the signal high and varies, I'd trust that the engine IS rich and > pursue that problem. > I am going to have to buy a better VOM. The one I have (digital output) bounces around too much to really tell what the voltage is - I think its sampling rate is too slow to keep up with things. So I know the O2 sensor is working, but I don't have the resolution to tell if the O2 sensor thinks things are running on the rich or lean side. > > If you take the car to a shop with an emissions tester, they can put the > car on a lift, running, and check the emissions level in front of the > converter through the O2 sensor's mounting boss. Then, they can burn a > small hole through the pipe just after the converter and check the emissions > there. (They'll close the hole when they're done.) That will tell whether > the converter is working. And that is the only valid test that I know of. > > > Yes. But I don't want to spend more money on testing until I've exhausted the simple causes. Since HC and NOx levels are good and O2 is at 0%, things point to a rich mixture rather than a bad cat. Since water temp sensor is working and O2 sensor appears to be working, I'm leaning towards leaky injectors. But before I pull them and send them off for cleaning and rebuild, I'm going to try tightening the AFM spring and take it in for a second test. I'm so close to passing that I want to minimize my work. Thanks, Charlie > Rich Wagner > Montrose, CO, USA > '82 GTV6 -- to be removed from alfa, see http://www.digest.net/bin/digest-subs.cgi or email "unsubscribe alfa" to [email protected]
