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98 Mistique OBDII code 1131

08-12-2007, 12:36 AM
I have a OBDII code of 1131 Lack of HO2S1 Switches-Lean (Bank 1 sensor 1). The check engine lite comes and goes. This is a 4 cylinder engine in the Mistique. Any good Ideas as where to check? MAF sensor was just cleaned. I'm getting poor gas mileage too, around 19MPG VS: 28MPG not too long ago.

08-12-2007, 02:00 AM
does your car smell like rotten eggs? or hear a slight rattle under the car? when the engine like comes on its usually emissions. signs of a catalytic converter going bad is gas mileage and your engine light coming on/ flashing while driving

08-14-2007, 08:20 PM
2001jettavr6 (http://www.automotiveforums.com/vbulletin/member.php?u=527726) ...nope no smells or loss of power....Cat is not rattling and doesn't seem to be plugged. Does anyone know what sensors would be involved in this problem?

08-15-2007, 11:44 AM
Its the upstream 02 sensor. If your running lean, I would guess youve got an intake leak somewhere. I would rule the cat out.

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