Jovial

Nomad327, If I follow what you are saying about the waste spark system, newer Subarus would have the front and rear plug on one side fed by one coil and the other side fed by another coil. If the same plug (front?, rear?) always has a reverse polarity spark, material would be transferred from the large, ground electrode to the small center electrode. On the forward polarity spark the material transfer would be from center to ground. In the case of copper plugs, the ware would be uniform due to similar metals for both electrodes. The double platinums would also wear uniformally due to the platinim square on the ground electrode, but they will wear more slowly than copper. With the single platinum plugs you would see more wear in the reverse plugs because the platinum center does not transfer materail as fast as the large, ground electrode. So how do I know if my ignition has this two plug pre coil waste spark system?

This weekend I had the code reset to see if it would come back right away. So far I have 70 miles on it with no light. I have been driving it in the same way as before, but no rain this time. Perhapse excessive amounts of rain over a couple of days is enough to keep the exhaust temperature down causing the fault. I just bought this car so I have no idea when the fuel filter was changed last. That would be something to try prior to replacing O2 sensors. Is there a way to check if the sensors are operating properly?

Subarube, Are you having CEL codes popping up for the cat system? For $10 I'd be willing to try this to clear up my P0420. Jovial

Ok so I have some questions right away. "P0420 "Catalyst efficiency below threshold (bank 1)"" What is bank 1? "Finaly the FSM states that you have to inspect the inside of the cat converter before deciding it's bad. (posted by Frag 3-20-04)" What do you look for in the converter to see if it's bad? "1. Use correct grade of good quality gas." Would reformulated gas be a problem? The manual says it's ok but should you go with a higher grade like 89 octane? "2. Ensure correct spark plugs installed." I heard that platinum plugs are bad and copper plugs should be used. Any truth to that? "3. The factory manual says if there are no other trouble codes showing, to (1) check for leaks in the exhaust system, or (2) remove the front and rear catalysts and check for damage at the face of the catalysts. (posted by Harborseal55 2-1-04)" Face of the catalysts meaning gasket faces? "4. I would start by clearing the code. If the code returns then I would replace the rear sensor. (posted by 99obw 12-24-03)" If the problem is intermittent, could there be some environmental factor? Is there a way to check if the sensor is bad?

I have recently purchased a 97 Legacy L with 68K on the odo. A couple of days ago the CEL came on. I had it checked and it came up P0420 "Catalyst efficiency below threshold (bank 1)". I'd like to generate a discussion specifically regarding this code, it's possible causes, suggested trouble shooting/solutions, and actual fixes or attempted fixes. I've done a search on the site and it seems that others are experiencing the same thing. I know that modified engines/exhaust systems are prone to this but that should not be the case for stock vehicles. Modded vehicles bring there own particular problems so let's stick to "stock" solutions if possible. Many of us have to pass emissions so ignoring the code is not an option. I'll try to compile here the information that I have seen (I have tried to give credit when possible). Let's discuss them and please add, correct or clarify. Some notes. A. The FSM indicates that this code could also be triggered by a fault with either O2 sensors circuit (upstream and downstream). If so, there should also have been another code indicating that. Moreover, even with no O2 sensors at fault, the P0420 code could be triggered by a leak in the exhaust system (air entering the exhaust system). Finaly the FSM states that you have to inspect the inside of the cat converter before deciding it's bad. (posted by Frag 3-20-04) B. AFAIK the replacement interval for Subaru O2 sensors is 100,000 miles. (posted by 99obw 12-24-03) Suggested solutions. 1. Use correct grade of good quality gas. 2. Ensure correct spark plugs installed. 3. The factory manual says if there are no other trouble codes showing, to (1) check for leaks in the exhaust system, or (2) remove the front and rear catalysts and check for damage at the face of the catalysts. (posted by Harborseal55 2-1-04) 4. I would start by clearing the code. If the code returns then I would replace the rear sensor. (posted by 99obw 12-24-03) 5. Replace the catalytic converter. Any other suggestions? What have you tried? What worked/ didn't work?