Ignition Distributor System Tests (1988-1995 3.0L Chrysler, Dodge, Plymouth)

TEST 11: Other Misfire Causes

So you've done all of the spark tests, and still your Chrysler (Dodge or Plymouth) car or mini-van, but the misfire and/or rough idle is still there. Well, here are a couple of suggestions that might help:

1. The valve cover gaskets are leaking oil onto the spark plug wells and soaking the spark plugs and spark plug wire boots in oil.
   • Over time, this oil will cause a misfire as the oil cooks and turns into carbon tracks.
   • The photo above shows you what a carbon track looks like on the inside of the spark plug wire boot and on the ceramic insulator of the spark plug.
2. Engine Compression Test
   • One of the most overlooked diagnostic tests to find the root cause of misfire is the compression test.
   • You'll need an engine compression tester of course.
   • The engine compression readings between cylinders should not vary more 15%.
3. Carbon tracks on the spark plug(s) and in the inside of the spark plug wires.
   • The the orange arrows in photo above point to what carbon tracks look like.
   • Replace the components as affected with carbon tracks.
4. Broken Spark Plugs.
   • This usually happens at tune-up time, if you have dropped one on the floor.
   • You power washed the engine, this is something that should never be done on any vehicle.

If this info saved the day, buy me a beer!