As the carmakers include more features and new kinds of driveability and emissions controls into their cars, scanner manufacturers have to follow the lead of the carmakers and make their tools fit the cars on the road.

While the four-valve cylinder does have the advantages of high rpm for racing and other high-speed purposes, that’s not what they’re for in most of the ordinary cars we see in the shop.

In important and unexpected ways, the information in wiring diagrams is our most valuable diagnostic tool; so most good mechanics use them frequently for just such troubleshooting.

A’87 Merkur XR4ti with no heater fan on all speeds except High. The customer also mentioned that he had recently begun to notice a few drops of oil on his garage floor and an occasional hesitation problem on moderate acceleration, primarily in second and third gears.