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1996 Honda Accord P0420 Causes?
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GoatTamer
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Jul 2, 2012, 7:44 AM
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1996 Honda Accord P0420 Causes?
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Hello all, I have a 1996 Honda Accord LX 2.0L with ~293k miles. Since I bought it a year ago, the exhaust has always had a slightly rich smell - but no sulfur eggs smell. A year ago, I had replaced both bank 1 and bank 2 O2 sensors which cleared out two previous CEL codes, and it then passed emissions just fine. I haven't had a CEL until now.
After looking online for possible solutions, I went to an auto parts store to get a reading off the O2 sensors. The bank 1 sensor fluctuated rapidly from .05-.70, and bank 2 was more stable from .70-.76.
The only other thing I've noticed is that if I turn the A/C on while idling, the idle gets rougher, occasionally dropping from near 700RPMs idling to 300, and sometimes gets into a cycle of dropping to 300, then revving to 700, then repeating.
The most common solution seems to be replacing the catalytic converter. But, I've also read that they rarely fail on their own, and that there's usually something wrong pre-cat that made it clog up. I've been told to buy OEM for durability, but I need to know what I can do to make sure the new cat doesn't get clogged up 6 months from now.
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Discretesignals
Ultimate Carjunky
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Jul 2, 2012, 8:22 AM
Post #2 of 9
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Re: 1996 Honda Accord P0420 Causes?
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What were the previous trouble codes?
Need to monitor long and short term fuel trims at different engine operating conditions. The rotten egg smell is an indication that the catalyst is working. You can't tell the rich and lean trend by watching O2 voltages unless you graph them out over a long period of time or unless they hang at a certain voltage range for too long (low switching).
When the idle is surging with the ac on what is the compressor clutch doing? Does it only surge when the ac is on?
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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GoatTamer
Novice
Jul 2, 2012, 9:02 AM
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Re: 1996 Honda Accord P0420 Causes?
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I can't find my personal records in diagnosing the first problem, but I know one was P0141 and I believe with 95% certainty the other was P0135 - they were both circuit malfunctions.
I wouldn't know how to identify what the compressor clutch is doing, but the idle only surges when the A/C is on, otherwise perfectly normal.
If these don't help at all,
- What would you suggest as the most cost-efficient solution if emissions are coming up in a month?
- Would a local parts store monitor these trims or voltages for free using the same diagnostic tool?
- Can I pay a mechanic to diagnose the problem and then attempt to fix it myself?
- It looks like swapping out a cat isn't much more than unscrewing some bolts, if that is what I will need to do. I haven't noticed any rattling when driving, and when I tapped the cat nothing rattled either. Is it likely that the cat will "recover", or is it time to drop the dough?
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Hammer Time
Ultimate Carjunky
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Jul 2, 2012, 9:47 AM
Post #4 of 9
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Re: 1996 Honda Accord P0420 Causes?
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PO420 is nearly always going to be a bad cat. It's almost impossible to meet all the criteria that code requires any other way. I've only seen it be something else once and that one was a crack right in front of the cat but after the upstream sensor.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Hammer Time
Ultimate Carjunky
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Jul 2, 2012, 11:35 AM
Post #6 of 9
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Re: 1996 Honda Accord P0420 Causes?
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293K is a reason
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Hammer Time
Ultimate Carjunky
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Jul 2, 2012, 12:31 PM
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Re: 1996 Honda Accord P0420 Causes?
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Of course, if it really was rich. You didn't have any codes indicating that.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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GoatTamer
Novice
Jul 2, 2012, 3:31 PM
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Re: 1996 Honda Accord P0420 Causes?
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Thanks for your time!
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