Here I am diagnosing a problem with a Chevy 2.8L S-10 engine. It is a ’89 model and had a miss. Actually when you start it up cold it runs well for a few minutes, the it starts to miss mildly and by the time it heats up it is a dead miss.

The simplest thing I can do is pull spark plug wire off the plug ends, or off the distributor. If you pull a spark plug wire off a cylinder and the engine starts to miss worse, that cylinder is OK. If you pull a wire off a cylinder that does not change the way the engine runs, that is a dead cylinder.

Once we locate the dead cylinder, we have to determine why this particular spark plug is not firing. Or why that cylinder has a miss. There are several easy tests we can run to get a definitive answer. The only tools you need are a spark-plug wrench for the 5/8th” plugs, a cheap compression gauge (about 10 to 15 bucks at Sears), and a standard sized Phillips screwdriver.

The first thing I do after I locate the dead cylinder is take the spark plug wire off of the dead cylinder on the plug side, while leaving it plugged into the distributor cap. I then put the round end of the phillips screwdriver in the hole in the end that went over the plug tip and hold the metal part of the screwdriver about 1/4″ away from the engine block. (Unhook the coil wire so it won’t start)..Have someone turn the engine over, if there is a spark, it will jump the 1/4″ gap with a snap. Don’t hold the metal shaft, hold the plastic handle or you will get zapped, it won’t hurt you.

No spark may mean a bad wire, distributor or coil. This engine has spark, so the next test is to remove the spark plug and examine it. If it is real sooty and black, it may be fouled out from too much gasoline. If it is covered with hard bluish stuff, the plug may be fouling out due to excessive oil entering that cylinder.

Next we will take a compression test. Test the bad cylinder first. If it has no compression, you may have a burnt valve or a hole in the top of a piston. If it has some compression but it is low, then more than likely you have bad piston rings in that cylinder. A compression test of the other cylinders will tell you if they are within specs too.

Once I get my compression test completed I can give this man a diagnosis. If it has no compression in the dead cylinder, the motor is done, since it has over 200,000 miles on it. Quite frankly, the whole vehicle is a real junker, and if it needs a replacement engine, a good used engine is a great choice. You can buy engines at an affordable price at GotEngines.com. Call us now @ 1-888-344-8044.

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