As technical editor for Babcox, I frequently receive e-mails and letters from readers who ask me for free auto repair advice. Most of these requests are not from professional automotive technicians, but from motorists who have seen one of our publications while visiting a service facility somewhere.
One guy in particular seems to think I’m his personal auto repair consultant. His name is Charlie. I’ve never met Charlie or talked to him on the telephone. Even so, every couple of months, Charlie sends me a two- to three-page hand-written letter describing his latest problem with his 13-year-old car (which has nearly 150,000 miles on the odometer) and everything he’s done in an attempt to fix it. He carefully describes all the symptoms (hesitates, sometimes runs rough, hard to start on cold mornings, jerks and bucks, but only at slower speeds, etc., etc., etc.), and lists all the parts he’s replaced since his last letter (his local parts store must love him!). Then he asks me what I think is wrong with his car and what part(s) I think he should replace next.
I want to tell Charlie to replace his car.
But instead I’ve made the mistake of making an educated guess and offering some suggestions on what I think might be causing his latest troubles. Unfortunately, this just encourages Charlie to run down to his local parts store and replace anything and everything I said might be wrong with this car! Then he writes me back another letter saying that (1) my suggestions fixed his problem, or (2) they didn’t fix it, or (3) that he now has a new problem and wants more free auto repair advice.
From now on, I’m giving Charlie and others like him the best free repair advice anybody can offer: Take your car to a reputable independent repair shop and have it professionally diagnosed and repaired.
I can always make an educated guess as to what might be causing a particular problem, but it’s only a guess and nothing more. Without first-hand access to the vehicle and hooking up some diagnostic equipment, there is no way to know for sure what might be causing a rough idle, hard starting, hesitation or other driveability issue. There are too many things that can cause similar driveability symptoms to say off the top of my head what’s wrong or what I think needs to be replaced. Even with a scan tool, scope and multimeter, it’s hard to nail down the cause of some driveability problems.
The engine might have a bad sensor (if so, which one?). It might be an ignition problem (spark plugs, wires, distributor cap, rotor, ignition module, coil pack, crank sensor or what?). It might be fuel-related (dirty injectors, leaky fuel pressure regulator, weak fuel pump, plugged filter or return line, or maybe bad gas). It might be mechanical (a burned valve, jumped cam timing, worn rings/cylinders, leaky head gasket, worn cam lobe, broken valve spring). It might be electrical (low battery, a charging problem, bad ground connection, a wiring fault). It might even be some combination of factors that’s causing a problem.
Yet Charlie (and others like him) wants me to look into my magic crystal ball and tell him what’s wrong with his car so he can “save money” and fix the problem himself. Sorry Charlie, no can do.
I’m tellling him to take his car to a repair shop and have someone with the proper skills and equipment figure out what’s wrong with it. Instead of guessing and throwing parts at the problem, the shop should be able to accurately diagnose the vehicle using basic test procedures.
A technician can plug a scan tool into the vehicle to check for diagnostic trouble codes, to read sensor and other system data, to review freeze-frame data that may shed light on a fault, and to perform other diagnostic tests. He can also use his scan tool to look at short-term fuel trim and long-term fuel trim to see if the fuel mixture is running abnormally rich or lean. If need be, he can hook up a digital storage oscilloscope (DSO) and examine sensor waveforms for abnormalities, or ignition patterns for obvious problems. He may use an infrared exhaust analyzer to look at the composition of the exhaust gases for additional diagnostic insight. Or, maybe all he needs to do is check fuel pressure with a gauge, or intake vacuum or cranking compression to isolate the fault.
The bottom line is this: Armchair advice is no substitute for hands-on diagnostics. It never has been and it never will be. And people like Charlie need to be told this.
Yes, it will cost your customers. Diagnosis is often the toughest part of the job, so it’s only fair that shops charge for their diagnostic time. Diagnosis requires expensive scan tools and other test equipment that must be constantly upgraded and updated. It also takes considerable training and experience to stay up-to-date with changing technology and all the different makes and models of vehicles that are on the road today. So if your shop charges a $75 or $100 “diagnostic fee,” it’s not a rip-off. It’s the best bargain your customers will ever get. And most importantly, it will save them the cost and frustration of replacing a bunch of parts they didn’t need.
That’s my advice.