Even "smart" guys can have...
Even "smart" guys can have difficulties diagnosing a variety of engine problems. Follow along as this story shows them how do to it correctly.
Within the Pontiac community, there are many who are very good at physically working on their cars. Changing parts, swinging motors, and the like comes very naturally to them. But when chasing a problem, you need to first determine what has to be changed.
The art of diagnosing is a gift that not everyone is blessed with. In much the same manner that the medical field has surgeons (those good at swapping parts in and out) and diagnosticians (the ones who tell the surgeons what to do), so does the auto business. When your Pontiac isn't running correctly, you first need to be a diagnostician before you can be a surgeon.
The reason for the problem may be obvious, such as a ruptured radiator hose or a burned ignition wire. All too often, the cause of the engine performance issue is not so easy to spot. It can be very elusive. An engine has a synergy between its operating parts, and a failure in one area can induce a false symptom in another. In dentistry, they call this sympathetic pain. With cars, we call it an exercise in frustration.
Many feel that a proper method of diagnosing is to simply replace everything in sight and hopefully stumble upon what is wrong. Though that theory is eventually effective, it's very costly and time consuming, and doesn't speak well for the knowledge of the mechanic.
This isn't meant to say that at times it isn't a proper diagnostic step to replace a part with a known good component. This, however, should only be done when proper protocol points in that direction, and if the component is not serviceable. For example, it's not necessary to identify which circuit in the HEI module is causing a no-start condition, but it is important to accurately determine that it's the module and not the coil. Since there is no means or reason to try and repair the ignition module, it's replaced as a unit after it's determined to be faulty.
Diagnosing requires a very good knowledge of the working theory of the engine or individual part. If one is chasing a cold-start issue, a carbon-clogged EGR valve isn't where the proper diagnostics will lead you: Pinging will bring you there. But if you aren't familiar with the function of the EGR system, it can become suspect. Thus, the first step in finding a problem is to reference the proper Pontiac shop manual to see if it provides a flow chart with some helpful hints on where to look.
Another aspect of diagnosing is that the procedure often defines what isn't broken instead of what is. For example, if you are chasing down a rough idle problem and don't find a vacuum leak, you still don't know the cause, but you have eliminated an air leak as a possibility. The list of potential reasons has just got shorter.
Having made a career of diagnosing mechanical problems, I have a term that I use when I teach seminars for the auto industry: SAT, Stop And Think.
The first step in finding a problem begins in your mind. Did I disturb something accidentally while I was working on another part of the car? Does the condition only appear under certain temperatures, operating loads, engine speed, and so on? Can another area be impacting or causing the problem, such as the alternator?
A few minutes looking under the hood and studying the engine while thinking the problem through will usually lead to a more proficient diagnostic, and may very well quickly reveal the cause. Even the best and most experienced diagnostician has been led astray by a series of events, or by taking shortcuts. The best results are usually realized with a thorough and analytical approach.