Good morning
At 110000 miles I replaced the spark plugs and at just short of 111000 miles, I had the timing belt and water pump replaced plus a couple of other problems detected at that time including an A/C clutch that was failing.
Last week, I noticed that there was a definite hesitation upon acceleration both from a stop and when passing. For example, on one occasion I floor boarded it at about 35 mph to overtake a slow truck on the highway and there was about a 1/2 second delay before anything at all happened.
I took it to my mechanic the next afternoon. The system was not throwing any codes and the hesitation had improved at least 50% by then. They hooked-up their elaborate Snap-On test equipment that plugs into the OBD2 port and determined that the primary (upper) O2 sensor is working fine and the secondary (lower) O2 sensor performs erratically and even stops working. Then, they did a heat sensor test on the cat. I don't know the exact readings but, from my memory, the top end was "about right" at something like 560 degrees and the lower one was more than 100 degrees cooler (perhaps around 400 degrees or ??), indicating at least a partially plugged cat and a bad lower O2 sensor.
I asked if there was any way we might try "cleaning-out" that cat since I just didn't feel it should be failing so soon (I'll explain more below as I get to the question). I had a full tank of gas so, they suggested an octane boost. I added a pint of 93% rubbing alcohol to the tank and the plan then was to run mid-grade/higher octane fuel for a while and see what happens. I'm a little reluctant to change the O2 sensor yet (and, maybe I'm wrong on this) because I'm thinking it's a result and not a cause of the problem with the cat.
Having thought about this some, here is the background and why I think the cat loaded-up. The next trip after I replaced those spark plugs, I made my usual 12-mile commute to work without incident. On the way home, I made a side-trip that made the return commute some 25 miles and most of that went without problem. When I got about three miles from home, the engine began to miss and got worse and worse and began throwing a flashing check engine light. I stopped, left the engine running, looked things over and then shut if off, checked oil, re-started it and all was fine until I resumed driving. Well, I made it home with a great deal of problems, basically running on three cylinders, very jerky and a heavy blue hue behind me of what I assume was raw fuel. I parked it in the driveway, looked things over and, finding nothing; I took our 02 Civic down to the Auto Parts store and bought an inexpensive OBD2 car reader. The 03 Civic (the one with the problem) was throwing only one code indicating a #1 cylinder misfire (I don't now have the note but I believe it was the P0301 code). I fairly quickly determined I had not gotten the spark plug wire/coil securely seated and it had lost contact - - that problem solved. But, putting this all together, I am now suspecting all of that to have caused the cat and O2 sensor problem I am now seeing.
My questions are, basically, around avoiding replacing the cat and the likelihood it can be cleaned/leaned-out. Is the increased octane, over time, likely to help some (btw, the car runs quite well right now)? Is there anything else we can do? Is something like this Seafoam treatment likely to help? (http://www.superhonda.com/tech/carbon_cleaner_treatment_how-to.html )
Thanks.
Don
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Sunday, August 9th, 2009 AT 1:45 PM
