You will have to test it or have it test.
Here's possibles causes:
Use of leaded fuel
Damaged HO2S
Malfunctioning ECT
High fuel pressure
Damaged exhaust manifold
Damaged catalytic converter
Oil contamination
Cylinder misfiring
Downstream HO2S wires improperly connected
Damaged exhaust system pipe
Damaged muffler/tailpipe assembly
Retarded spark timing
We can't how much will it cost before knowing what's the problem.
It can be something as stupid as a bad connections or might have to change your catalytics converter.
Nic.
Contour 99 MTX V6 fully loaded, stock with 110000km. Illuminated sunroof switch. About to do the mystique rear dome light conversion with eyeball dome light.
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