bigmoose wrote:Just a thought that may or may not help. With the black goo in the front of the catalyst, it sounds like the exhaust may be cooling too much under certain run conditions. When I drove a 97 HX civic with lean burn, they put the catalyst right in the exhaust manifold. I don't know where the Insight's catalyst is, but perhaps you could increase the exhaust temperature getting to it by wrapping the exhaust pipe from the engine to the catalyst with exhaust heat wrap tape? The extra temperature might elevate catalytic activity in the bed.
bigmoose, Holy smokes that's a great suggestion: the Insight is built exactly the same way: a teeny tiny header coming right off the side of the engine, the cat "hangs" from that downward to the bottom of the car. There's not enough header to wrap (the thing is TEENY) but I COULD start the wrap the the cat's flange and move backward to the end of it.
By the way: that MIGHT also help mileage, especially if it allows the cat to heat up faster. The computer cares about NOx emissions and will richen the mixture when it thinks there's too much oxygen in the exhaust.
dnmun wrote:i second this. i was thinking the same thing but i figured it would require wrapping the entire tailpipe with rockwool or fiberglas insulation to keep it hot.
also if you have a lot of blowby now that is pushing a lot of oil through the motor into the exhaust then maybe it needs some new rings. i assume they use fewer rings for friction so maybe they just wear down faster.
would it help to use a different oxygen sensor, or a new one?
dmun, I've been thinking about this very thing. I fear piston blow-by, as it's something I really can't fix myself. I replaced the PCV valve in anticipation of this - if the PCV valve chokes off the pulses, that can increase blow-by.
FYI: both the upstream and downstream O2 sensors are "new". I replaced them with genuine Honda parts when I first got the P0420, hoping that would help. It actually "accelerated" when the P0420 appears. I kinda wish I had the old ones back but I discarded them. Not smart.
I'm considering two options:
- re-remove the cat and flush it with a solvent, possibly using a parts washer to circulate the solvent. Maybe gasoline, maybe lacquer thinner.
- the EGR valve on these cars has been known to gum up. Might be time to pull that and check it. There, again, the solvent wash might help.
I'm "up to" 35 miles before the P0420 light comes back on. That's significant progress - before the "wash", it was about 12 miles.
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