How To Fix Oil Leak On A 3.1 Liter Engine

General Motors switched over to a DIS ignition system on the 2.8 and 3.1 liter engines. Before this change was made these engines had distributors so they capped that hole with a plug and an o ring seal. This o ring begins leaking over time and must be replaced to stop the engine oil leak.

The procedure is much like pulling a distributor shaft. This is located on the left side of the engine, below the throttle body. The shaft is held in place by a half round clip and a 13 mm bolt. I have included some pictures below.

First you need to remove the air duct that runs from the throttle body to the air filter housing. Next unhook the 3 vacuum lines from the throttle body. All 3 vacuum lines come together into one fitting.

Next detach the throttle body from the intake plenum by removing the two bolts. There are two coolant lines that run from the throttle body that must also be removed. You can leave the accelerator cables hooked up to the throttle body. Unplug the power connections to the Throttle Position Sensor and the Idle Air Control Valve.

Gently pull the throttle body away from the plenum and set it aside. Take some carburetor cleaner and spray into the throttle body to clean any sludge buildup. Next loosen the two fuel line fittings from the fuel rail and carefully move them over a little.

Back the bolt out that holds the shaft assembly and remove the half round clip. Take some pliers and pull straight up on the shaft and pull it completely out of the hole. You will see the O ring that sits in a groove in the shaft. This is what needs replacing. If you don't want to go OEM on the replacement O ring you can go to the auto parts store and ask for a Fel-Pro part number 70800. It is a good idea to go ahead and get a new throttle body gasket also.

Work the new O ring from the bottom of the shaft upwards and into the groove in the shaft. It helps to put some oil or petroleum jelly on the shaft and O ring to move it easily up the shaft. Drop the shaft back down in the hole. It will hit the gears but probably won't drop on down in there until the gears line up. You can try lifting the shaft back out and rotate it some each time before dropping it back in the hole.

The easiest way to make it line up and drop in there is to disable the ignition and use a remote start button to bump the engine a few times and it should drop right down then. Replace the clip and bolt and tighten to torque specs. Hook the fuel lines back up and Install the new throttle body gasket and reattach the throttle body to the plenum. Insert the vacuum line fitting back into the throttle body. Hook the coolant hoses back up along with the power connections for the TPS and the IAC. Reattach the air duct and crank the engine. There should be no more oil leak.