O2's or Cats? - TCCoA Forums
 
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post #1 of 7 (permalink) Old 08-03-2008, 09:28 PM Thread Starter
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O2's or Cats?

Ok on my 97 4.6 I had my whole exhaust done about a year ago, custom cat back with 2 1/4" duals with a midmounted magnaflow, ever since I purchased the car 2 years ago roughly once every 6 months (rarely) the engine light comes on for catalyst effiency below threshold bank 1, now it has moved to bank 2..... this vehicle regularly sees 25,000miles a year if not more so its obviously not a frequent occurance but the car is at about 109,XXXmiles currently, should I change out all the o2's or replace the cats? or both?

Just looking for feedback. Thanks.

-1996 Pearl White Thunderbird 4.6 Sport 4v with many mods:
Current Best: 13.583 @ 103.74 10/2014.
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-2001 White Ford F-250 Super Duty 6.8 V10, 4-door, 4x4, Limo Tint, BFG KO2's, Bilstein 7100 Remote Reservoir Race Bypass Shocks, 6" Spring lift, Kenwood Double Din, K&N Intake, FlowMaster Exhaust
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Last edited by Chris_Murder; 08-03-2008 at 10:31 PM.
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post #2 of 7 (permalink) Old 08-06-2008, 07:02 PM
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Only the second O2 sensors on each side monitor the cats. The cats on these cars do tend to fail at just over 100k, so I would put my money on your cats are dead and not your O2 sensors.

"I'd rather push a Ford than drive anything else."
Current Cars: 2008 Taurus X (84k) 1997 Lincoln Town Car (145k) - 1996 Mercury Cougar (260k)
Previous Cars:2003 Mazda 6 (160K) - 1990 Mercury Cougar (168k)- 1977 Lincoln Town Car (141k) 1996 Lincoln Mark VIII (116K) 1997 Lincoln Continental (212k) 2002 Mercury Mountaineer (92k)
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post #3 of 7 (permalink) Old 08-06-2008, 07:08 PM
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Has it moved from Bank 1 to Bank 2 (meaning it is no longer on Bank 1) or is it now on both? I would look at the oxygen sensor data with a scanner and see how well it is switching before replacing anything.

Also, while the rear oxygen sensors are the only ones that monitor catalyst efficiency, the calculations are based off of data from the front ones, so the front ones can contribute to these kinds of problems.

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post #4 of 7 (permalink) Old 08-07-2008, 06:31 PM Thread Starter
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it occasionally throws either code P0420 or P0430 bank 1 below efficiency threshold , or bank 2 below efficiency threshold. Also I know that there are 2 sets, the front controls air fuel ratio and the rear only check efficiency.

-1996 Pearl White Thunderbird 4.6 Sport 4v with many mods:
Current Best: 13.583 @ 103.74 10/2014.
227hp/241tq measured on calibrated mustang dyno, tested at full vehicle simulation with inertia enabled, no number skewing.
-2001 White Ford F-250 Super Duty 6.8 V10, 4-door, 4x4, Limo Tint, BFG KO2's, Bilstein 7100 Remote Reservoir Race Bypass Shocks, 6" Spring lift, Kenwood Double Din, K&N Intake, FlowMaster Exhaust
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-2005 White GMC Sierra 3500 6.6 Duramax, Dually, 4-door, 4x4, Limo Tint, BFG Commercial T/A's, Rancho RS9000XL Shocks, Kenwood Double Din, K&N Intake, Banks Monster Exhaust
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post #5 of 7 (permalink) Old 08-07-2008, 07:07 PM
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Well, if the car is running great (indicated that it's unlikely the cats have clogged or broken up), I would suspect the oxygen sensors.

--Chris

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post #6 of 7 (permalink) Old 08-07-2008, 07:12 PM Thread Starter
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alright next paycheck I'll swap them for new ones

-1996 Pearl White Thunderbird 4.6 Sport 4v with many mods:
Current Best: 13.583 @ 103.74 10/2014.
227hp/241tq measured on calibrated mustang dyno, tested at full vehicle simulation with inertia enabled, no number skewing.
-2001 White Ford F-250 Super Duty 6.8 V10, 4-door, 4x4, Limo Tint, BFG KO2's, Bilstein 7100 Remote Reservoir Race Bypass Shocks, 6" Spring lift, Kenwood Double Din, K&N Intake, FlowMaster Exhaust
Amber_Murder's Daily Driver.
-2005 White GMC Sierra 3500 6.6 Duramax, Dually, 4-door, 4x4, Limo Tint, BFG Commercial T/A's, Rancho RS9000XL Shocks, Kenwood Double Din, K&N Intake, Banks Monster Exhaust
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post #7 of 7 (permalink) Old 08-18-2008, 03:51 PM
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Quote:
Originally Posted by Chris_Murder View Post
it occasionally throws either code P0420 or P0430 bank 1 below efficiency threshold , or bank 2 below efficiency threshold. Also I know that there are 2 sets, the front controls air fuel ratio and the rear only check efficiency.

I got those same codes, would switch from one to the other. My car ran fine for about a year then started to ping, then ran a little rough. I got new cats and they havent came back, and its been 6 months since I had them replaced. Car runs smoothly now.

1997 Mercury Cougar XR7 Sport 4.6L
P.I. Intake, Mustang T/B and Upper Plenum,B&M Heavy Duty Trans Cooler, Trans Temp Gauge, A/F Ratio Gauge, K&N Cone Filter, Air Silencer Delete, 50% Front 20% Rear Tint, A&A Fiberglass GFX Kit, Xenon Front Clip, Magnaflow High Flow Cats

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at least Ford can pay their bills and not go on welfare like GM and Chrysler.
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