First Time Seeing this CEL

[Trctnless]

"P0420 Catalyst System Efficiency Below Threshhold (Bank 1)

ANy Takers on what this is pointing too? Drove into the MTNS today, pretty significant elevation change maybe 1200- 5000 ft. o2's still cycled normaly, EGT looked normal even in the uphill twisties..

Thanks

facts
15psi
Blow thru
BARO wire clipped
crankcase is ventilating
charcoal can ventilating.

IDLE +5
MID -10%
WOT -5%

 

[Doug99RS]

HA... sorry, just recognize something.

Anyways, it just means that the downstream o2 sensor has determined that the exhaust gases passing through it have higher levels of hydro-carbons than desired. The largest part of your problem is your test pipe. With no cat, it's going to polute more.

Now before you mention the year and a half (or so) that you've been running the test pipe you've got to remember what happens as a car gets older. More blow by (there's always some so it doesn't necessarily indicate a problem), leaking valve stem seals, carbon build up on pistons, valves, intake runners, and so on. You may want to run some Mopar Combustion Chamber Cleaner to help get rid of those parasitic build-ups.

I think the difference between now and when you first put the down-pipe on is that the engine itself is not running nearly as clean as it used to. I ran a gutted cat for a little while and used that resistor from radio shack (that you didn't care for on another forum) and occassionally threw a check engine light. It wasn't all the time so the engine is running right on the verge of efficient and polluting.

The higher altitudes you just drove at probably didn't help. High altitudes, low oxygen content and it probably caused your engine to run slightly richer that in Charlotte or central NC.

If you don't want to run the resistor in the o2 I don't see any other option short of putting a hi-flow or full stock cat. Do you know something that will work better?
Doug

 

[Trctnless]

"HA... sorry, just recognize something."

hehe, As is Life.

""If you don't want to run the resistor in the o2 I don't see any other option short of putting a hi-flow or full stock cat. Do you know something that will work better?""

Nope I don't but i'm going to button up things a little more as you may have read I have a few leaks to take care of. Those items and a Tank of fresh 93 in my normal driving environment and see if it comes back. Will it clear itslef? I haven't cleared the CEL yet.

""High altitudes, low oxygen content and it probably caused your engine to run slightly richer""

no doubt.

The MCCC is on the to do list. I may very well do the resistor mod if it continues to throw the code. Environmentaly speaking a HF cat is probably the best fix.

Thanks

 

[Doug99RS]

You'll probably need to go ahead and clear the codes out. Some components will run a test multiple times and turn off the light when the problem is no longer there. Others are designed to set the code and leave the light on until you have the problem fixed.

If you're teatering on the edge of throwing a code and not throwing it then a high flow cat of any kind should put you back in to the safe range by a good bit.
Doug