How many miles on your SL2?
Ok, we know we need a cam cover gasket. The oil that leaks into the plug well can break down the insulation on the plug wires and cause misfires.
Number 1 plug is sooty and definitely running rich. Have the pulgs been replaced? How many miles ago? What type of plug. NGKs are factory. I've used AC Delcoes. Work well and are inexpensive. Stay away from platinum plugs. Expensive and don't work well with the type of ignition in Saturns.
Have the plug wires been replaced? How many miles ago? What type?
Have the O2 sensors been replaced? Both or which one? What kind? You mentioned that you were told the O2 was bad before and it was not the problem. What was the problem?
Low voltage on the front O2 sensor (PO131) indicates a lean condition. This can be caused by a vacuum leak. Check the vacuum lines for leaks, especially the PCV line and the brake booster line.
Saturns do not use Mass airflow sensors (MAF).
PO141 ididcates a heater circuit malfuntion in the rear O2. It is either in the O2 itself or the voltage supplied to the O2. The voltage being supplied to the rear O2's built in heater is either low or nonexistant. Have the voltage checked at the rear O2.
PO171 also indicates a lean condition. Again first check for vacuum leaks. Less likely is a dirty fuel filter or low fuel pressure as a cause.
Multiple misfires (PO300) most likely causes are plugs, wires, corrosion on either the coil towers and/or coil mounts, and a stuck EGR valve.
The two codes that indicate a lean condition are confusing considering the carbon covered plug and the black smoke from the tailpipe. The rich condition this indicates can ruin a catylitic convertor. The good news is "Good compression".
I would start with the most likely and least inexpensive fixes. New plugs, clean or replace wires, clean the coil towers and mounts, replace cam cover gasket, clean the EGR valve, check for proper voltage at the rear O2 wires, and check for vacuum leaks.
Sunday, February 19th, 2006 AT 7:18 AM