bmwrepairs: How to do CYLINDER DROP TEST on 2005 Bmw 325?

Diagnosis & Testing

Prior to diagnosis or testing procedures, visually inspect the components of the ignition and engine control systems. Check for the following:

Blown fuses

Poor spark plug connections

Damaged or corroded ignition wires

Damaged or worn electrical insulation

Discharged battery or low alternator output

Ignition module multi-connector condition

Damaged, corroded, or loose electrical connections

Excessively worn, defective, or damaged spark plugs

Excessively worn or damaged distributor cap or rotor

Check the spark plug wires and boots for signs of poor insulation that could cause shorting or crossfiring. Make sure the battery is fully charged and that all accessories are off during diagnosis and testing. Make sure the idle speed is within specification. Check all of the fuel injector electrical connections.

Cylinder Drop Test

WARNING

When performing a cylinder drop make sure the cylinder's high-tension lead for the cylinder being checked is sufficiently grounded. Failure to do so may cause severe and expensive internal component damage.

Fig. These pliers are insulated and help protect the user from shock. They also prevent the plug wires from being damaged

A cylinder drop test can be performed when an engine misfire is present. This test helps determine which cylinder is not contributing to the engine's power. The easiest way to perform this test is to remove and ground the plug wires one at a time for each cylinder with the engine running.

Place the automatic transmission in P , and the manual transmission in Nand engage the emergency brake. Then start the engine and allow the engine to reach a warm idle.

Using a spark plug wire-removing tool, preferably, the pliers type, carefully remove and ground the ignition wire from one of the cylinders.

WARNING

Make sure not to touch any part of the car that is metal. The secondary voltage from the ignition system is a high-energy spark, and although it is not deadly, the voltage is significant enough to cause a painful electrical shock.

The engine will sputter, run worse, and possibly nearly stall. If this happens reinstall the plug wire and move to the next cylinder. If the engine runs no differently, or the difference is minimal, shut the engine off and inspect the spark plug wire, spark plug, and if necessary, perform component diagnostics as covered in this section. Perform this test on all cylinders to verify which cylinders seem low on power.

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