XPost: sci.electronics.repair, alt.home.repair   
   From: this@address.is.invalid   
      
   On 23-04-2023 15:56 Scott Dorsey  wrote:   
      
   >>How could 50 to 100 clearings of the OBD codes (using a dumb OBD reader)   
   >>cause the catalytic I/M readiness monitor to set after months of not   
   >>setting?   
   >   
   > It cannot.  But the fact that you've got 50 to 100 clearings of the OBD codes   
   > makes your general maintenance process very suspect.   
      
   The question isn't about how horrible a person I am but whether or not   
   running gas:water could have (probably temporarily) increased the   
   efficiency of an old cat (or whether clearing an engine control unit buffer   
   could have enabled the cat readiness monitor to be more easily set).   
      
   As for your negative comment about my maintenance skills, I must not have   
   been clear although I thought I was detailed enough with the dozen steps   
   listed. I don't care about the cat efficiency unless I have to smog.   
      
   Then, all of a sudden, I care about two things   
   [1] I care that there are no pending or set codes (especially P0420)   
   [2] I care that the readiness monitors are set (especially the cat)   
      
   You don't seem to know engines well, so allow me to explain that when the   
   engine sees a misfire in 1 out of 200 revolutions (most cars), the engine   
   control module permanently shuts down the spark to that cylinder (to   
   protect the cat).   
      
   This is permanent.   
      
   [1] The engine is running but at some point the engine noticeably stumbles   
   [2] The CEL goes on and the cylinder will be off forever   
   [3] Even if you drive for the 300 miles or so that the gas tank can do   
      
   There are only 2 things that will undo that permanently shut off cylinder.   
   [1] Either you turn the engine off and start it back   
       (in which case the code is still there but the spark is back again)   
   [2] Or you clear the codes   
       (in which case the code is gone and the spark is back to that cylinder)   
      
   Then the cycle repeats anew.   
      
   This is well known so if you don't know it you just don't know engines well   
   and that's fine because this question is about the cat and not the engine.   
      
   Could the water:gas mixture, somehow, have increased the cat efficiency?   
   Could the hundreds of code clearings, somehow, have wiped out a buffer?   
      
   >>[1] The check engine light has been on, on the dash, almost constantly   
   >>[2] Mostly when I looked, it would be P0420 bad cat pending & set codes   
   >>[3] I've been going through this regimen now, for about five or six years   
   >>[4] I didn't need smog for more than a year so I didn't worry about codes   
   >   
   > What this means is that the O2 sensor downstream of your converter is   
   > reading an incorrect value.  This could mean your converter is bad, or   
   > maybe that the O2 sensor is bad, or maybe that the connector is bad.   
      
   When I got the Mitsubishi Lancer 2004 for $200 it had this problem then.   
   I replaced the oxygen sensor (there appears to only be one upstream sensor)   
   and that alone fixed the problem for the first smog about 5 or 6 years ago.   
      
   There are no oxygen sensor codes.   
   I need to repeat that because the oxygen sensor is not showing any codes.   
      
   That means the oxygen sensor is getting the correct voltage, the wires are   
   fine (although there could be an intermittence I guess), and the input and   
   output are fine.   
      
   I repeat there are no oxygen sensor codes.   
   Therefore, I see no reason to suspect the oxygen sensor on a mere whim.   
      
   I've noticed a lot of people replace the sensor whenever they get a code   
   but that's what the tests are for on the sensor itself. If the sensor were   
   bad, it would show a code of a bad input, output, or power connection.   
      
   It doesn't.   
      
   > If other codes were set too, it could have been all kinds of other things.   
   > If you're seeing incorrect values on both pre and post converter   
   > sensors, you'll see other codes, and that could be the result of all kinds   
   > of misfiring issues or mixture control issues.   
      
   It's only the P0420 and there is only one bank so it's for the cat.   
      
   "The P0420 code signals a low catalyst system efficiency. This code   
   suggests that the oxygen levels are below the desired threshold (Bank 1),   
   which most often results from problems with your car's exhaust or fuel   
   systems."   
      
   I'm sure it's the cat.   
   I just don't want to replace the cat.   
      
   And, get this, it passes smog without me doing anything but clearing the   
   P0420 code and letting the readiness monitors (especially for the cat) set.   
      
   The problem isn't passing smog because it generally took a few months of   
   driving to finally set the readiness monitors after clearing.   
      
   The question is only whether clearing the codes hundreds of times allowed   
   some kind of "buffer" to be wiped out in the engine control module - or -   
   as someone else suggested - maybe the water in the gas increased the   
   efficiency (somehow? chemically?) of the catalytic converter?   
      
   >   
   >>[5] When it came within months of smog time, I cleared the OBD codes   
   >>[6] Mostly either the code comes back or the readiness monitor won't set   
   >>[7] But once in a while, the readiness monitor does set so I rush to smog   
   >   
   > Have you considered actually finding and fixing the problem instead of   
   > constantly resetting the error?  You're not doing your engine or your   
   > gasoline bill any good this way.   
      
   There is no problem other than the cat is the original 2004 and it has low   
   efficiency, and, as a result, every once in a while the P0420 pops up and   
   the readiness monitor for the cat takes hundreds of miles for it to set.   
      
   >>[8] I did that - it passed smog - but failed for a hose in bad condition   
   >>[9] I painted the hose black so that it would look like it's brand new   
   >   
   > Wow, with maintenance like that it's a wonder your car runs at all.   
      
   There was absolutely nothing wrong with the hose & it's expensive to   
   replace. It passes smog. It would have cost about $100 bucks to replace.   
      
   Painting it accomplished essentially the same function as replacing it   
   given there was nothing functionally wrong with the hose at that time.   
      
   It just didn't pass a visual inspection. I would have passed it. He didn't.   
   He wanted me to do a repair right then and there at his gas station.   
      
   I refused. I think he just wanted business by claiming the hose was bad.   
   There was nothing I could do other than pay him and never go back there.   
      
   There was nothing wrong with the hose from a functional standpoint.   
   If it actually fails, then I'll replace it. But I'll wait for it to fail.   
      
   It doesn't seem like you understand engines at all by the comments you're   
   making. This is a car that cost $200 five or six years ago. Not a Tesla.   
      
   It has an old 2004 tired low efficiency catalytic converter. That's all.   
      
   If I'm not going to replace a hose that isn't broken, I'm certainly not   
   going to replace a catalytic converter that isn't broken either.   
      
   It passes smog.   
      
   [continued in next message]   
      
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