February 8, 2012
By Jim Kerr; photo courtesy Brown’s Auto Centre
“Driveability” encompasses a very wide range of vehicle problems, from transmission shifting to hard starting. Driveability problems can cost a lot of money and time and if you ask most technicians, they are also often the hardest type of vehicle problem to diagnose.
A while back, I had the task of locating a driveability problem on an older Buick. The make and model are not important because this story is typical of many cars and trucks on the market. This owner, let’s call him Bob, had a hesitation or stumble in his car whenever he was cruising at 80 km/h. The hotter it was outside, the more the problem appeared, but when he stepped on the gas, the car accelerated fine.
Bob does a little of his own work, but hadn’t had a tune-up in a long time, so he took the car in and asked the mechanic to do one. The sparkplugs were replaced, timing was checked, and all the other usual inspections were done. Everything looked good. The next warm day, Bob was driving the car and the stumble was still there. Disgruntled, Bob took the car to a different repair shop and told them what had been done. This shop rechecked everything the first shop had done, took the car for an extensive test drive over a period of days, and got the car to act up. They determined the problem only occurred just as the clutch in the transmission’s torque converter locked up (engaged) at 80 km/h, and that the problem was with the transmission. After charging for the diagnosis, they sent Bob to a transmission repair shop.
The technician at the transmission shop drove the car and thought the problem was not in the transmission, but rather it was a problem with the engine. Now Bob was totally disgusted! He had spent several hundred dollars and still didn’t have the car fixed. Off to a third repair shop.
This shop went through all the diagnostics, confirmed it was indeed a transmission problem, charged him (of course) for the time spent, and sent him on his way. Back to the transmission shop! Bob told them it had been checked out by two repair shops, and both had told him it was the transmission. Then Bob told them to overhaul the transmission! Twenty-five hundred dollars later, the problem was still there. Then Bob came to see me.
I just happened to have a group of students working on driveability problems at the college where I teach automotive mechanics, so I told him we would take it on as a project.