1996 Saturn SL2 Oil on Plug Misfire Fix

Welcome to the forum.

Plugs, wires, and a new cam cover gasket will help out a lot. What was the exact code?

[quote:7b2df6dacf="peppermrj"]What was the exact code?[/quote:7b2df6dacf]

Thanks for the reply. I don't know what the exact code was. I took it to Auto Zone and had them plug it in and the person who did it immediately said it was the 02 sensor. Next time I'll ask for the code.

In reference to the oil in the plug well, do you think I might have a bad piston ring?

I doubt if the rings could get that bad. It is just a leaky gasket.

Most all have to do with three things.
Wiring/connection problem
O2 itself
An exhaust leak.

Remeber that 96 and newer models have two O2 sensors. One in the exhaust manifold and the other at the end of the catylitic convertor. Both can set a code. The one in the exhaust manifold provides the PCM info for adjusting the air/fuel ratio , therefore the engines performance. the one at the end of the cat is for checking on the function of the cat and the first O2.

Good luck and post back with your results. :)

Ok, I went back to have the codes checked and this time 4 codes came back:
P0131
P0141
P0171
P0300

They told me both O2 sensors were showing codes, multiple misfires (which I knew), and possibly a fuel pressure problem, MASS, or Ignition problem.

I pulled the plugs again and this time the #1 plug was dry but there was black soot on each plug contact. There is also black soot coming out of the tail pipe. I had a cylinder compression test done and was told the pressure was fine. I don't know what to do next.

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 [b:270af433b8]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. [/b:270af433b8]

There is about 200000 miles on my SL2. I don't have the mileage in front of me as to when I changed the plugs and wires last but it was less than 6 months ago. That was the first thing I did last time it was missing like this and it didn't fix it. Back then it was showing an o2 code as well, which I had mentioned before. Back then the catalytic converter was bad so I had it replaced. It ran great up until now.

Now yesterday when I pulled the plugs to look at them again all the plug wells were completely dry. But as I said black soot on all the plugs. I'm thinking possibly what I thought was oil on the plug and in the well could have been gas. It didn't smell like gas but with all that soot the gas would have looked like oil. Today I'm going to go ahead and change the plugs and wires again and see what that does. With all the black stuff I'm sure it needs new plugs and wires but I'm thinking if that helps it will only be a temporary solution. It'll start acting again in a few months or weeks.

As to vacuum leaks, how do you check to see if there is a leak somewhere? I don't see anywhere on my engine where there is a missing or damaged hose. Is there a test that can be done. Or a trace?

There should be a diagram of the vacuum lines on a sticker under the hood.

Have either of the O2s ever been changed?
If not I'd say it might be time to bite the bullet and replace them. The recommended change interval is 100,000 miles. I have 130,000 on my SC2 and have yet to change the O2. Knock on wood. A bad front O2 will cause rich running, poor gas mileage and ruin your cat. At least change the front O2. Do not use any grease on the electrical connection. Believe it or not the O2 takes in outside air thru that connection!

Could your cat be plugged again? Can be tested for with a vacuum gauge. You can also remove the front O2 sensor and see if it runs better. If it does it might be the cat.

The valve cover leak is a slow leak.The plug wells fill up with oil but it takes a while. If the plug wires are that new I'd clean them using some waterless hand cleaner and reuse them. That is unless they have a lifetime gaurantee and don't cost you anything to replace.

Have you ever cleaned the EGR valve and it's port? Have you ever cleaned the throttle body?

Get a volt meter and make sure you have 12 volts to the Rear O2's heater circuit.

good luck and let us know what doin.

:D Problem resolved!!!! Hopefully. I changed the front O2 sensor, took it out on the interstate and it ran smooth as silk. Went by Auto Zone had them reset the codes, took it back out on the interstate and still no Service Engine Soon light. Thanks to everyone for the advice. I'll definitely be coming back occasionally out of interest and for advice. I've also recommended this website to friends. Keep up the good work. :lol: