OK if the spark plugs are worn to a point that it can't burn all the fuel then it tries to burn the rest in the cat. The vents to the heater pull air in from the outside unless set on recirculate which is only on A/C max. So if it can't burn off all the excess gas it will load up in the exhaust, making the cat smell like a rotten egg and such and can get pulled back into the car through the vents for the heating/A.C. System. Besides if the car has never had the plugs replaced it is way overdue anyway so it won't be money wasted if anything your mpg will increase so it will be money saved down the road. Let me know how it goes after the new plugs. I would prefer A/C delco plugs platinums will last around 80,000 between changes. Gap them to the specs on the label under the hood.
Friday, September 11th, 2009 AT 10:15 AM