P0420 code
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P0420 code
99 Civic EX sedan 270k miles.
ran low on oil for a long time. The replacement oil pan leaks around the gasket.
Newer (in the past 3 years) cat and 02 sensors.
I have a cheap $20 scanner...the generic P0420 code keeps coming up sometimes after 30 miles and sometimes after 300 miles and i keep resetting it. I bought some Guaranteed to Pass emissions stuff , but I sort of knew I was kidding myself.
http://www.crcindustries.com/product...-oz-05063.html
I have until July until my last emissions test which is just a scanner hookup (I think the scanner they use cost more than 20 bucks).
I don't want to throw parts and $$ at it. I want to diagnose and fix but I don't really know where to start.
ran low on oil for a long time. The replacement oil pan leaks around the gasket.
Newer (in the past 3 years) cat and 02 sensors.
I have a cheap $20 scanner...the generic P0420 code keeps coming up sometimes after 30 miles and sometimes after 300 miles and i keep resetting it. I bought some Guaranteed to Pass emissions stuff , but I sort of knew I was kidding myself.
http://www.crcindustries.com/product...-oz-05063.html
I have until July until my last emissions test which is just a scanner hookup (I think the scanner they use cost more than 20 bucks).
I don't want to throw parts and $$ at it. I want to diagnose and fix but I don't really know where to start.
If you think a good mechanic is expensive, try hiring a bad one
Joined: Dec 2011
Posts: 32,017
Likes: 256
From: Midwest. Aiming about mid-chest
Rep Power: 519 
Re: P0420 code
Needs a cat
If it's "in fuel control" and has no exhaust leaks, it needs a cat.
Long term oil consumption and poor running (or rich or misfiring) can cause premature cat failures....and you seem to have had both?
Although 270k is not premature
If it's "in fuel control" and has no exhaust leaks, it needs a cat.
Long term oil consumption and poor running (or rich or misfiring) can cause premature cat failures....and you seem to have had both?
Although 270k is not premature
Re: P0420 code
Cats wear out over time. The precious metals wear off the substrate and go out the tailpipe over time, so no amount of cleaning will fix it. Degradation is accelerated by burning oil, misfires, burning coolant or fuel control problems. After all, you recently had a distributor problem, which will burn up the cat very quickly. You most likely need a cat. However, exhaust leaks can cause the ECU to set a P0420 code too, so make sure you don’t have any exhaust leaks before changing the cat.
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Joined: May 2017
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Speaking of throwing $$ at a problem with no plan and shoddy diagnostics...this is what I've done in past 5 years.
Fuel pump and filter.
Starter.
Ignition switch.
distributor
sort of unrelated...power steering pump
someone else did the cat/o2 sensors and alternator (not at the same time)
She seems to be running pretty decent now...no obvious misfires or codes except for the 420 stoner code. Plenty of power with just a little bit of that distrib rattle.
Without sounding too stupid...what is the best way to search for exhaust leaks?
Will they be mondo obvious?
Fuel pump and filter.
Starter.
Ignition switch.
distributor
sort of unrelated...power steering pump
someone else did the cat/o2 sensors and alternator (not at the same time)
She seems to be running pretty decent now...no obvious misfires or codes except for the 420 stoner code. Plenty of power with just a little bit of that distrib rattle.
Without sounding too stupid...what is the best way to search for exhaust leaks?
Will they be mondo obvious?
Re: P0420 code
Exhaust leaks won’t always be obvious. The easiest way I know of to find exhaust leaks is by shoving a rag in the tailpipe, then clamp another rag over it so it doesn’t blow out. This will build pressure and make leaks more obvious. Next, start the engine and pour a little Seafoam in the intake. The smoke should only come out the tailpipe. If you have a leak, smoke will come out of the leak too, making it obvious where the leak is.
If you think a good mechanic is expensive, try hiring a bad one
Joined: Dec 2011
Posts: 32,017
Likes: 256
From: Midwest. Aiming about mid-chest
Rep Power: 519 Re: P0420 code
this is what I've done in past 5 years.
Fuel pump and filter.
Starter.
Ignition switch.
distributor
sort of unrelated...power steering pump
someone else did the cat/o2 sensors and alternator (not at the same time)
What sort of cat is it? (discount cats tend to fail quickly)
What's been happening with your engine that can shorten the service life of the cat?
(oil consumption, distributor issues, and believe it or not simply running out of gas can damage a cat)
She seems to be running pretty decent now...no obvious misfires or codes except for the 420 stoner code.
Plenty of power with just a little bit of that distrib rattle.
Without sounding too stupid...what is the best way to search for exhaust leaks?
Will they be mondo obvious?
Will they be mondo obvious?
Have someone stuff and hold a thick rag in the tailpipe to help make leaks more apparent while the engine is running
improvise a stethoscope using rubber tubing, listen along the pipes and manifold
Smoke check it
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