What Causes the Engine in a 1994 Pontiac Grand Prix to Make a Tapping Sound?
Your 1994 Pontiac Grand prix was offered in the base trim level with a well known 3.1-liter six-cylinder and a four-speed automatic transmission. If you don’t know anything about the 3.1-liter, or the internal workings of an engine, a ticking noise could be one of a thousand things, as far as your concerned. Funny thing is, most people don’t understand from a service side of view the 3.1-liter has well known problems; not unlike most engines in use today. Knowing the common faults and failures is the key to determining the cause of a ticking noise, in this case with your 3.1-liter.
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The drama
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Most back yard mechanics; let alone real mechanics, will tell you that the 3.1-liter is well known for blowing head gaskets. Most 3.1-liter early model GM engins; this includes Chevy and Pontiac, were known for this failure, but it doesn’t have much to do with a ticking noise. So be warned, as soon as you mention “3.1”, someone is likely to blurt out “head gasket”, but with a ticking noise this isn’t even likely to be the case. Ticking can be caused from several different problems, but unless coolant is pouring into your crankcase; but even then, you will likely experience way worse than even a loud tick while the engine is running.
Lifters
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Your 3.1-liter valve train is driven by a block mounted camshaft that uses lifters to transfer mechanic operation from the camshaft lobe to the push rod, and eventually to valve to open it. A sticky lifter will not return to its normal operating position and cause a ticking noise; whenever the cam attempts to open an intake or exhaust valve. This is normally cause from a worn or faulty lifter, followed by a damaged lifter due to overheating or lack of oil and/or oil delivery. A sticky lifter making a tick isn’t too bad of a problem,; the engine will normally act as it generally does, with a little extra noise. Still, it’s a good idea to inspect the reason for a stick lifter, it could be a serious lack of oil delivery; a condition related to clogged oil delivery or drain passages.
Piston Slap
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General Motors; I.e. the manufacturer of Chevy and Pontiac vehicles, has been noted for their defects related to the well known GM piston slap. Piston slap is when there is too much clearance between the piston and the cylinder wall. If your ticking noise sounds like its coming from the top side of the engine this isn’t likely the case; but from the bottom end, this is a likely cause from your 3.1. In general light piston slap is a problem most GM six-cylinder engines are subject to, and some engines last for hundreds of thousands of miles. Be warned though, eventually you will have to over bore the cylinders or get a new engine or engine block when it finally becomes a serious issue.
Other Likely Causes
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Basically, your crankshaft turns the camshaft via a chain. The cam shaft pushes upwards on the push rods, through a lifter and pushes up on the rocker arm, which pushes down on the intake or exhaust valve. If your rocker arm, push rod or camshaft has become worn, a slight ticking noise will develop as a result of the excess clearance from the wear. Sometimes extra thick oil additives like Lucus and motor honey will help solve the situation and ticking noise, but this is only a temporary fix and will mask real mechanical problems that should be addressed.
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