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Joined: Jun 2003
Posts: 80
CEG\'er
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OP
CEG\'er
Joined: Jun 2003
Posts: 80 |
Just looking for some support here. I got the dreaded P0420 (Bank 1 Catalyst System Efficiency Below Threshold) code. I went ahead and graphed the performance of the O2 sensors, figuring that is the problem. The sensors before the cats ran even with each other for the most part, but the ones after were a different story. I've got the pic below. The part where bank 2 drops off is when I started putting on the gas. As you can see, the bank 1 sensor is all over the place at idle. I seriously doubt I have a cat going bad. Think it's the Bank 1 02 sensor #2?
I ran a search already!
99 Ford Contour SVT - SOLD!! 
'90 CRX Si, '98 Explorer V8, '98 Acura ITRally Co-Driver
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Joined: Nov 2002
Posts: 3,506
Hard-core CEG'er
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Hard-core CEG'er
Joined: Nov 2002
Posts: 3,506 |
Im not familar witht he graphs, but coming form apersona stand point, id swithc out the O2 sensor first...its way cheaper than cats...if that does not fix it, then its probably a bad cat, you could always Gut the Pre-Cats and run Mil Eliminators.....that woudl be the simplest thing to do, if that were the case.
Lupe
3.0 SVT hybrid...all the fixens...Track/Race ready very soon!!!!!! 20,000 + miles
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Joined: Jun 2003
Posts: 80
CEG\'er
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OP
CEG\'er
Joined: Jun 2003
Posts: 80 |
for the graphs, if you look you'll see voltage values. the lower the graph, the less oxygen being detected by the sensors in the emissions. however, I can't see how the banks can be so different at idle by so much. I figure if bank 1 drops off, bank 2 would naturally drop off. but I could be wrong. 
I ran a search already!
99 Ford Contour SVT - SOLD!!
'90 CRX Si, '98 Explorer V8, '98 Acura ITRally Co-Driver
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Joined: Sep 2002
Posts: 1,788
Hard-core CEG\'er
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Hard-core CEG\'er
Joined: Sep 2002
Posts: 1,788 |
Don't compare the two downstream sensors to each other.
Compare each downstream sensor to its respective upstream sensor.
Your B1-S2 graph looks like an upstream sensor graph. That means the cat is dead. Upstream sensors should switch back and forth just like your B1S2 graph while at idle. The downstream sensor should change much more slowly as the cat processes the exhaust.
Dead cat. If in warranty, have the dealer replace it. Otherwise, consider the option above of gutting it or just installing MIL eliminators.
Steve
98 Contour SE Sport 2.5 Duratec ATX The wifey's car
89 Taurus SHO - 246K miles
94 SHO ATX - 190K
1997 F-150 5.4L ATX - The Workhorse 150K.
ANY THREAD WITH "OMG" or "WTF" ETC IN THE TITLE WILL BE IGNORED!
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