can a faulty upstream ho2 sensor give a false read of multiple misfire


Asked by May 19, 2015 at 09:16 PM about the 2004 Pontiac Grand Prix GT1

Question type: Maintenance & Repair

car is automatic,series 111,,and when I pull it down in first gear and get up to about 25 kms it begins to bog,,however if I increase the speed to about 55 kms it comes out and has power to spare, it is NOT the mass air flow sensor,,it has been duly cleaned and vent checked for sticking,also I can hear the bog out of exhaust at higher speeds of 120 and beyond,and the engine light will flash,,ive changed everything electrical there is,ex plugs wires coils,ignition plate,EGR valve pc valve is ok too,,,diagnostics show faulty oxygen sensor and multiple misfire . Head gasket not leaking,there is a slight spark knock when car is floored,but only briefly.,,

3 Answers


Sounds like you need a tune up (new spark plugs and spark plug wires). If you have over 160,000 km on your Grand Prix you're over due for a tune up. As part of the tune up check both the primary and secondary resistance values on the coil packs. If one is bad, replace all 3. HTH. - Jim


found out the cars transmission has to be paired up with the computer,,to shift and not bog out,,thanks for your help

1 out of 1 people think this is helpful.

Thank you for letting us know. You're welcome. Glad to help. Glad you have it fixed. -Jim

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