Here’s a list of some of things I do… note some of the items require a specialized scanner/tooling
- remove oil filter, cut back media, take magnifying glass and bright light and look for a German sparkle party (chunks of metals)
- general blow- by test.. cap dance test to look for evidence of loss of cylinder compression
- injector smooth running test looking at injector correction values. Scanner states any values over 5 indicate a failed injector, but really that’s when you’ll start getting actual misfire codes and a value of 2 mu^3 is suspect in my book
- mechanical cylinder compression test if you have the tooling.. if not, an appropriate scanner can do an electronic compression test where it looks at oddities in the cam lobe timing while cranking. Of course this test is only good if timing is spot on
- does it have oil, is there anything odd with the oil (water or coolant)
- chemical inspection of coolant for possible head gasket leak(s)