2002 4.3 V6
I started getting intermittent/random misfires when really pushing it (1000lbs in the truck going 70mph in third gear up a 5-6% grade) that would disappear as soon as I pulled back.
Considering most (if not all) of both ignition and fuel side was replaced, I started looking for other possible causes.
Someone suggested that primary O2 sensors might not be up to task (after 300k+ miles) so I decided to change them.
Soon after changing them, I got a CEL. P0420 (Catalyst System Efficiency Below Threshold Bank 1)
I looked up the O2 voltages and, just as expected, Bank 2 was perfect (primary going all over the place, secondary varying very little) while Bank 1 was dead (secondary sensor voltage followed primary's almost perfectly with a short delay)
I checked the temperatures and, once again, as expected, Bank 2 was working fine (catalyst temperature higher that the pipe going in) while Bank 1 was doing nothing (catalyst temperature was at least 100F lower than both in and out pipes)
So, it turns out, Bank 1 cat REALLY doesn't work but now I have three questions:
1: How is it possible that I never had that code before? Was the primary sensor THAT bad that it hid the problem?
2: Is there any way to "clean/renew" that catalytic converter or do I need a new one? I read about trying an "Italian tune-up" while using premium gas (I can do that), using some varnish cleaner (I don't want to do that) or some snake oil-looking "catalytic converter cleaners" (not sure about that)
3: Should I consider replacing the secondary sensors too (now or after fixing the cat)?
Help?
I started getting intermittent/random misfires when really pushing it (1000lbs in the truck going 70mph in third gear up a 5-6% grade) that would disappear as soon as I pulled back.
Considering most (if not all) of both ignition and fuel side was replaced, I started looking for other possible causes.
Someone suggested that primary O2 sensors might not be up to task (after 300k+ miles) so I decided to change them.
Soon after changing them, I got a CEL. P0420 (Catalyst System Efficiency Below Threshold Bank 1)
I looked up the O2 voltages and, just as expected, Bank 2 was perfect (primary going all over the place, secondary varying very little) while Bank 1 was dead (secondary sensor voltage followed primary's almost perfectly with a short delay)
I checked the temperatures and, once again, as expected, Bank 2 was working fine (catalyst temperature higher that the pipe going in) while Bank 1 was doing nothing (catalyst temperature was at least 100F lower than both in and out pipes)
So, it turns out, Bank 1 cat REALLY doesn't work but now I have three questions:
1: How is it possible that I never had that code before? Was the primary sensor THAT bad that it hid the problem?
2: Is there any way to "clean/renew" that catalytic converter or do I need a new one? I read about trying an "Italian tune-up" while using premium gas (I can do that), using some varnish cleaner (I don't want to do that) or some snake oil-looking "catalytic converter cleaners" (not sure about that)
3: Should I consider replacing the secondary sensors too (now or after fixing the cat)?
Help?
