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How to Perform a Compression Test on the Engine in a Toyota Corolla

by Contributor

The Toyota Corolla comes with a 4-cylinder engine. When valves, piston rings and cylinder walls wear out, the engine loses power, burns oil or runs poorly. Performing a compression test is a quick, easy way to find out what is wrong inside of the engine without going to the trouble of tearing it apart.

Prepare for the compression test by warming up the engine in the Toyota Corolla. Performing the test on a cold engine produces inaccurate results. The battery must be in good condition, since it will need to spin the engine several times during the test.

Stop the engine and disable the ignition system to avoid electrical shock. Remove each of the four spark plugs, checking them for oil or damage, since these are signs of damage within the cylinder.

Place the compression tester in one of the spark plug holes and crank the starter. Rotating the engine builds compression in the cylinder, causing the needle on the gauge to jump. The last number that it jumps to is the compression number for that cylinder.

Write down the compression number and move on to the next spark plug hole. Repeat the procedure until you test all four cylinders and record the compression numbers. Compare these numbers to see if they fall within 10 PSI of each other.

Compare the compression numbers to the recommended compression ratio to see if they fall within 15 PSI. If the Toyota Corolla contains a 1.8L engine, the compression ratio is 10.0:1. However, if it is a 1.8L engine with 164 or 170 horsepower, the ratio changes to 11.5:1. For engines other than the 1.8L, check the vehicle manual for the appropriate compression ratio.

Perform the compression test again on any cylinders with a low compression number after adding a capful of motor oil to the cylinder. If the compression number increases, the cylinder has worn piston rings or cylinder walls. If the number stays the same, there are worn valves or valve seats instead.

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