I have a jeep grand cherokee with a straight 6 4.0 H.O. engine with approx 222000 miles, when it is cold out in the morning my jeep backfires after it getting over 2000 rpms, now i have replaced the fuel and air filter, the front pcv valve, the distributor cap and wires and plugs. My father says i have to much oxygen coming out with my exhaust because of amount of exhaust coming out.
Dec 31, 2012 at 3:09 AM