Mechanics stumble at finding cause of stall
Q: My granddaughter’s 1999 Buick Century started stalling when she slows down or comes to a stop. It is worse when warmed up and when fuel is less than half full. The car restarts and it runs fine otherwise. We have had it to three different mechanics. No error shows up as a computer code. We have replaced everything related to fuel and all miscellaneous sensors: throttle position sensor, fuel pump and fuel pump assembly, filter, spark plugs, wiring harness, crank sensor, cam sensor, to name a few. They found wires loose, connectors bent, and all kinds of odds and ends they thought might cause the stalling. We have not replaced the catalytic converter. We don’t want to junk it because the engine and transmission have been replaced and the front end has been completely rebuilt. Any ideas what might be wrong?
— M.G., Rockford, Ill.
A: When the transmission was replaced, did they also replace the torque converter? Did they flush the transmission cooler lines? What you describe is a classic symptom of a lockup torque converter that doesn’t release when coming to a stop. It can also be caused by plugged or restricted transmission fluid lines that run to and from the radiator.
Q: The right rear wheel brake cylinder on my 2012 Dodge Grand Caravan seized. What causes this and how can it be prevented? Will changing the brake fluid help? What can be done in an emergency? — W.U., Tinley Park, Ill. A: Corrosion inside the wheel cylinder may be the problem and
water in the brake fluid could be the root cause. Brake fluid, being hygroscopic, has an affinity for water, so changing the fluid occasionally may help prevent future problems. In an emergency, you may try backing up and applying the brakes. Another option is applying and releasing the parking brake. But we would not bet on either.
Q: In the past, with port fuel injection, I periodically added Techron fuel injection system cleaner to the gasoline to reduce injector pintle deposits and intake valve deposits. Now I have a Toyota 4.6-liter V-8 engine with direct fuel injection that uses a high-pressure fuel pump, in addition to the low-pressure fuel pump in the fuel tank. Can I safely add Techron?
— M.K., Essex, Conn.
A: Techron was developed to keep intake valves clean by piggybacking on the incoming
air/fuel mixture. Using Techron will keep your fuel injectors clean. Engines with gasoline direct injection (GDI) such as yours are prone to injector tip deposit buildup. Unfortunately, with GDI, the valves don’t get clean and no amount of additive in the fuel will help. Valve deposits are becoming a drivability problem once again.
Q: Regarding your column from May 22, I’d like to comment that the Sears mechanics used to do a light check as part of an oil change operation, a simple and critical part of maintaining a safe vehicle. Certainly more important than oiling a door hinge. There are more nonfunctioning lights on the road today than there ever used to be. I’d also like to see a light check take place during our required emissions check stops.
— M.T., Chicago A: Burned-out lights is another routine check we overlooked in our answer. Don’t hold your breath expecting the emissions testers (at least in Illinois) to check your lights. Do it yourself. In states with PMVI (periodic motor vehicle safety inspections), the lights get checked regularly.
Bob Weber is a writer and mechanic who became an ASEcertified Master Automobile Technician in 1976. He maintains this status by seeking certification every five years. Weber’s work appears in professional trade magazines and other consumer publications. His writing also appears in automotive trade publications, Consumer Guide and Consumers Digest. Send questions along with name and town to Motormouth, Rides, Chicago Tribune, 435 N. Michigan Ave., Fifth Floor, Chicago IL 60611 or motormouth.trib@verizon.net.