Easy Misfire Diagnostics with Oscilloscope. Narrow Down the Culprit WITHOUT Removing a Single Bolt.

Today we are acting out a fairly common scenario: You have a misfire (P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308) on a car where the affected cylinder is covered by the intake or generally difficult to get to. We walk you through the most common causes and show you how to quickly and easily use an oscilloscope to narrow down what system is at fault. The first test is a relative compression test to determine the compression relative to the other cylinders. Next we compare the ignition coil current ramps to each other using good and bad coils. Then we show fuel injector current ramps by adding resistance to an injector circuit to compare to the other coils. And finally we show you how to determine of the ignition coil is receiving a command signal from the ecm. These tests are pretty much universal for all gasoline vehicles. The only variable will be if the vehicle has direct injection, the injectors will likely draw higher amperage than what a port injection vehicle will draw. There are many more tests that can be done using a scope so if you would like to see more, let us know in the comments section.

Timeline
0:00 - Intro
1:05 - Relative Compression Test (Good)
5:01 - Relative Compression Test (Bad)
6:23 - Ignition Coil and Fuel Injector Current Ramp (Good)
10:09 - Ignition Coil Current Ramp (Bad)
11:40 - Fuel Injector Current Ramp (Bad)
14:51 - Ignition Coil Command Signal (Good)
15:14 - Outro