General Powertrain Diagnosis

Despite the sophistication of today’s powertrain control systems, even the most advanced software program cannot disguise a worn camshaft lobe, a burned valve or a loose timing chain. Unfortunately, even though these types of mechanical failures create recognizable symptoms of poor performance, many technicians get caught up analyzing pulse trains without ever considering valvetrains! The fact is, illuminated MILs (Malfunction… Read More

Computerized Powertrain Controls Diagnosis (Including OBD II)

Electronic engine control systems have been standard equipment on most cars and light trucks since the early 1980s. While these systems improve both driveability and fuel economy, their primary purpose is emission control. From a service standpoint, many of the early systems were difficult to diagnose due to their limited self-diagnostic capability. However, serviceability improved in 1988 with the implementation… Read More

Fuel And Air Induction Systems Diagnosis

Electronic Fuel Injection (EFI) was introduced to the automotive world in the late fifties, when Chrysler offered the ‘Electroinjector’ system as an option on its Hemi V8. Shortly after its debut, reliability problems forced Chrysler to recall the few sys­ tems that were sold. Ironically, re­ called vehicles were retrofitted with dual four-barrel carburetors. Three decades later the tide would… Read More

Diagnosing Computer Controlled HVAC Systems

Computer Controlled HVAC Pre OBD II Vehicles built prior to the advent of OBD II typically used electronic control modules only to operate their automatic temperature control systems. On these models, the control module was typically contained in the HVAC control head in the same unit housing the driver’s system control switches. Warning indicators may or may not be included on… Read More

A/C System Performance Testing Part 2

A/C Performance Testing A performance test can determine whether the A/C system is functioning properly and if it is not can indicate what is wrong so the system can be repaired.Different vehicle manufacturers specify different methods to conduct system performance checks, but as a guideline, the following procedure may be used.Connect a manifold gauge set as previously described. Hang the… Read More

A/C System Performance Testing Part 1

Automotive Refrigerants The refrigerant used in automotive air conditioning systems from their inception until the early 1990s was a chemical compound called dichlorodiflouoromethane, more commonly known as Freon or R12. R12 is a member of the chemical family known as chlorofluorocarbons(CFCs). Although R12 works extremely well as a heat transfer medium in an automotive air conditioning system, CFCs have been… Read More

A/C System Operation

A/C System Basic Principles In order to understand how an A/C system works, we must first understand a few basic principles. The first, and most important principle is that heat always moves toward a state of less heat. This is how an engine’s cooling system works. Heat created by the combustion process in the engine’s cylinders is transferred to the… Read More

Before You Buy an ASE Certification Study Guide

ASE Certification study guides abound. A quick search on Amazon yields well over three hundred results.  Before investing your money in any of these books, you should know the answers to the following questions: What Should I Be Certified In? What Tests Do I Need to Take? How Is the ASE Certification Program Set Up? What Does the ASE Say… Read More

Exhaust Systems Basic’s & Emissions Components

Exhaust System Basic Components The exhaust system is used to remove the burned air/fuel mixture, or exhaust, from the engine, away from the passenger compartment and out the back of the vehicle. The major components of the exhaust system are the exhaust manifold(s), exhaust pipes, catalytic converter(s), muffler and oxygen sensors. The AIR (Air Injection Reaction) system and EGR (Exhaust… Read More