What would cause my 1996 chevy silverado z71 to be running rich? its a heavy gas smell and i have no gas mileage any - Answered by a verified Chevy Mechanic ... 4/10/2010. Chevy Mechanic: Dan ... 1996 Chevrolet Silverado Z71 Off Road. Going through Ignition Modules every 200-miles. Has no cats.
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