Sonicfrog Posted June 20, 2009 Share Posted June 20, 2009 Yep. The problem is at idle. Both HC's and CO are too high. Max for HC at idle should be 100 ppm, mine measures at 275 ppm. CO should be 1.00 and is at 2.76. At higher RPM, HC's are at 18, and CO is at 0 ppm. The smog guy, not a registered smog mechanic, made a guess and suggested that it could be either the O2 sensor going bad, or cats going all fail on me. I did replace the O2 sensor last winter (broke the wires on the old one, FUBAR beyond repair) but that doesn't mean it hasn't gone bad. I don't want to throw a bunch of money around trying to get this fixed, because I don't have any (God I'm getting sick of being poor). Any one delt with something similar / have any suggestions??? Link to comment Share on other sites More sharing options...
OB99W Posted June 21, 2009 Share Posted June 21, 2009 (edited) The problem is not likely caused by catalytic converter failure. When both HCs and CO are high, it indicates a very rich mixture (either excessive fuel, or not enough air). Since the emissions drop at higher engine speeds, it means the mixture is not overly rich under that condition. Usually an oxygen sensor thats bad enough will cause elevated HCs and CO even at the higher RPMs, and especially since it was replaced not that long ago, probably isn't the culprit. One possibility is that the fuel pressure is too high, which could be caused by a problem related to the fuel pressure regulator. You could check that the vacuum hose connection to it is good, and also pull the vacuum hose off to make sure that there's no fuel in it (which would indicate a ruptured diaphragm). If you have access to a fuel pressure gauge, an actual measurement would be best. Do you have more than just the HC and CO readings? CO2 and O2 numbers could be helpful in determining what's going on. EDIT: The symptoms could also be caused by a MAF problem, although if only dirty that usually leads to a lean (not rich) running condition. Edited June 21, 2009 by OB99W Link to comment Share on other sites More sharing options...
Sonicfrog Posted June 21, 2009 Author Share Posted June 21, 2009 Do you have more than just the HC and CO readings? CO2 and O2 numbers could be helpful in determining what's going on. Idle (682 rpm) CO2 = 13.2, O2 = 0.0, HC = 275, CO = 2.76 High RPM (2340) CO2 = 14.3, O2 = 0.7, HC = 18, CO = 0.00 I didn't buy the cat failure thing because of the great readings at high revs. But I'm not an expert on such matters. PS. Man, I haven't been on the list for quite a while. I miss you guys. Link to comment Share on other sites More sharing options...
Gloyale Posted June 21, 2009 Share Posted June 21, 2009 Possibly PCV or coolant temp sensor. Link to comment Share on other sites More sharing options...
OB99W Posted June 21, 2009 Share Posted June 21, 2009 Idle (682 rpm) CO2 = 13.2, O2 = 0.0, HC = 275, CO = 2.76 High RPM (2340) CO2 = 14.3, O2 = 0.7, HC = 18, CO = 0.00 The CO2 and O2 numbers at idle are further indication that there's too much fuel for the amount of air available. The CO2 is a bit low, but more importantly, the O2 being 0.0% shows that the engine ran out of available oxygen to burn the fuel (and the catalyst had little or none to work with), resulting in high HCs and CO. Do you have a means of measuring the O2 sensor voltage? By the way, was the replacement sensor an OEM unit? PS. Man, I haven't been on the list for quite a while. I miss you guys. Awww, well come by even if you don't have a problem. Possibly PCV The PCV valve is normally open very little at idle, so if the valve or tubing were obstructed the idle mixture would typically only enrichen slightly. Still, it wouldn't hurt to check the PCV system operation. or coolant temp sensor. There are several possible causes of a rich mixture -- the CTS can be one if it tells the ECU that the engine is cold when it isn't. It would be good to determine if the ECU is remaining in open-loop operation, which is one of the reasons I'm asking if the O2 sensor voltage can be measured. Link to comment Share on other sites More sharing options...
Sonicfrog Posted June 21, 2009 Author Share Posted June 21, 2009 What should the voltage be to the O2 sensor? Link to comment Share on other sites More sharing options...
Legacy777 Posted June 21, 2009 Share Posted June 21, 2009 Voltage will cycle back and forth between 0 volts & 1 volts. Link to comment Share on other sites More sharing options...
Sonicfrog Posted June 27, 2009 Author Share Posted June 27, 2009 OK. Took the car to a Certified Smog Repair shop yesterday. There's good news and not so good news. The Good News: They say the O2 sensor is out, and that the injectors are clogged,. Those are easy to remedy. I'm going to get a new O2 sensor, and put some Seafoam in the tank. The Bad News: They say the front Cat is bad. How would one be able to tell if it's bad, and how would one tell if it's the front or back? I'm picking the car up from the mechanic this morning and will ask about that. Link to comment Share on other sites More sharing options...
OB99W Posted June 27, 2009 Share Posted June 27, 2009 OK. Took the car to a Certified Smog Repair shop yesterday. There's good news and not so good news. The Good News: They say the O2 sensor is out, and that the injectors are clogged,. Those are easy to remedy. I'm going to get a new O2 sensor, and put some Seafoam in the tank. I suggest you get an OEM O2 sensor. It would be useful to know what voltage(s) the shop read from the sensor that lead to the diagnosis. The Bad News: They say the front Cat is bad. How would one be able to tell if it's bad, and how would one tell if it's the front or back? Other than if the catalyst is found to be physically damaged, the only other way you can tell for sure if a cat is bad is to measure the exhaust gas composition before and after the cat. Some shops will do that by pulling the O2 sensor and measuring both there and at the tailpipe, and then comparing the numbers. If they don't see an improvement at the tailpipe, they assume the cat is dead. However, as I've explained before, if the engine is running so rich that there isn't enough oxygen left in the exhaust, the cat can't work (a cat oxidizes, but not if there's no oxygen to work with!). If you have the patience to read another long thread (I think you'll find it worthwhile), see http://www.ultimatesubaru.org/forum/showthread.php?t=76747 -- the poster had been told his high Hcs and CO were due to a bad cat, but I was unconvinced and eventually it was determined that the O2 sensor was misconnected. Resolving that fixed the emissions without replacing the cat. Since you intend to replace the O2 sensor, do that and check the emissions again after a ride to possibly burn off some cat contamination. As to the injectors being ''clogged'', that usually means they aren't putting out enough fuel, or that the spray pattern is uneven. Since you're experiencing a rich mixture, it would be more likely that if anything is wrong with the injectors, they would be staying open too much. The Seafoam probably won't hurt anything, but I'd start with the O2 sensor first. I'm picking the car up from the mechanic this morning and will ask about that. I'd be interested in reading what they had to say. By the way, did they check the fuel pressure? Link to comment Share on other sites More sharing options...
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