1996 Sable stumbles under load

Tiny
PROREC
  • MEMBER
  • 1996 MERCURY SABLE
I have a 1996 Mercury Sable wagon with 169K mi / 3.0L OHV engine. Recently the car has stumbled under load, especially when climbing a hill but also on level roads. The car lost power and the transmission came out of gear. The engine revved up so I pulled over and the transmission reengaged. I accelerated and everything was fine for a couple of miles then stumbled a little more but got me home. This has happened in the past. The ignition wires and plugs were replaced and that seemed to fix it. Those parts have only about 500 miles use. I also have a recurring P0420 DTC. No other codes present. I've shut the MIL off but it returns soon. Could my convertor be plugged and be causing this stumble? Could it be a worn 02 sensor? A clogged injector or the transmission? Perhaps a failing fuel pump? Thanks.
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Saturday, June 16th, 2007 AT 8:46 PM

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Tiny
MERLIN2021
  • MECHANIC
  • 17,250 POSTS
P0420 Catalyst System Efficiency Below Threshold (Bank 1)
Check the converter on bank 1 And if you have never changed the oxy sensors it's time!
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Monday, June 18th, 2007 AT 9:22 AM
Tiny
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Thanks for your input. Should the 02 sensors be changed even though they are not generating a code?

The highway mileage is 25mpg, city 12mpg. Just had the downstream 02 sensor changed on Bank 2.
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Monday, June 18th, 2007 AT 8:17 PM
Tiny
MERLIN2021
  • MECHANIC
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Most of the time 02 sensors won't throw a code. Some manufacturers say change at 50,000 mi, you be the judge!
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Saturday, June 23rd, 2007 AT 3:35 PM

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