1. Oil on Ignition Leads or on Spark-Plug part outside Cylinder

Oil on the ignition leads, or on the area of the spark-plug outside the cylinder is from the cam/valve-cover gasket (20$US gasket, lifespan is 55-70k miles for the rear bank and 70-90k miles for the front bank).

The gasket is not designed to be overtightened, it operates by forming a gap filling function between the head & cam cover which accommodates both flex of head/cam-cover & thermal expansion changes. Over repeated thermal cycling the elasticity of this gasket deteriorates until it can no longer perform a gap filling function and oil will seep past the gasket into the non-draining spark-plug-wells or down the front/rear of the engine. Ignition leads left in oil-wet wells will suffer degradation in their performance until a no spark condition results in that cylinder.

Solutions:
1) Every 6 months mop-out the small amount of oil that accumulates (usually in centre wells) by rolling up kitchen tissue into a tube and feeding this down the well & rotating it. Ignition leads must also be wiped clean and allowed to dry out - in the longer-term if neglected a miss-fire at that cylinder will result.

2) Retorque the cover slightly: do not overtighten, the torque is 5.8-8.0Nm which is finger tight. Torquing is to be peformed in a specific pattern as per "Cam/Valve-Cover Gasket" in "Section A)".

c) Replace the affected cam/valve-cover gasket replaced. The front bank is DIYable in 30mins, the rear bank requires 4hrs labour. The gaskets are 20ukp/20$US from Mazda Dealers. Details of the procedure can be found under "Cam/Valve-Cover Gasket" in "Section A)".

2. Oil on spark-plug base & electrode Inside Cylinders

Oil on spark-plug threads alone should not be confused with oil on electrodes. When removing spark-plugs even from seemingly dry wells, any oil hidden under the spark-plug-to-head washer will rapidly wick down threads.

Oil on the spark-plug electrodes is due to one of two things:

a) If all the spark-plugs are similarly wet, there is a problem and a compression test needs to be done to verify valve-guides are not worn. An extremely small number of 94 V6s suffered premature valve-guide wear, typified by compression around 120psi - all such engines would have had the failure several years ago.

b) More usually the electrode on only one spark-plug is wet, due to a blocked fuel-injector causing oil to be drawn through under vacuum. Injector cleaner (Techron/Redline-SI1/SI2/STP-Black-Bottle) in the petrol tank will resolve the problem.

Last Upload: 31st January, 2002. V1.50a
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