Saturn Engine >> ENGINE MISS OF POPPING NOISE

Saturn Engine >> ENGINE MISS OF POPPING NOISE

Engine Miss Or Popping Noise On
1991-97 GM 1.9L Engines VIN 8 & 9

The AERA Technical Committee offers the following information on an engine miss or popping noise on 1991-97 GM 1.9L VIN 8 & 9 engines. These vehicles
equipped with SOHC engines built before and including VIN VZ263139, either with LK0 or L24 engines, may miss or lack power under all normal engine-operating conditions. A popping noise may also be emitted through the exhaust manifold on deceleration or idle.

One cause of this condition is gum and/or carbon deposit accumulation in the exhaust valve guide(s) and on the valve stem(s). These deposits may cause an
exhaust valve(s) to stick open producing a misfire or noise. This condition may occur under all normal engine-operating conditions.

To prevent the possibility of gum or carbon deposit forming and causing the above-mentioned condition, a fuel additive is advised. Saturn suggests adding one 20 oz. bottle of Saturn fuel injector cleaner Part #21007313 or equivalent (fuel injection cleaner containing Techron) to a full tank of fuel. The fuel injector cleaner must contain Techron or gum deposits may not be removed from the valves and the valve guides. Caution: Adding a full 20 oz. bottle of injection cleaner to a partially filled gas tank may cause the fuel to create deposit formations on the valves and in the combustion chambers.

Machining the exhaust valve guide lower is also required to complete the repair. Using the service tool #SA9704E a pilot end mill and plastic stop, machine the exhaust guides from the combustion chamber side of the head. Apply pressure straight on to the guide so that no damage is done to the service tool. The plastic stop will make contact with the valve seat, shown in the figure below, when the end mill has cut the guide down. The approximate amount of guide removal is .406. For best results, oil or cutting oil should not be used. After the guide has been shortened, use a 7mm reamer or chamfering tool to remove any sharp edges left by the end mill.

The AERA Technical Committee

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