Accelerator pedal linkage should be examined on runaway car

May 2, 2009/Steve Tackett

MOTOR MATTERS ASK THE AUTO DOCTOR BY JUNIOR DAMATO

Dear Doctor: In the past three weeks while driving, my 1998 Buick LeSabre has “gone out of control” twice. Fortunately, I was not in traffic when these incidents occurred but on straight roadways. The engine rev-ed up and started bucking and going crazy. The only way I could stop it was to throw the shifter into Park and turn off the ignition. My mechanic has checked the computer and nothing shows up. He checked everything out, drove it for a full day and it ran fine. Do you know of anything that could be causing this? The car just hit 100,000 miles. Marge
Dear Marge: To date I have not come across a runaway Buick such as yours. The first thing I always check is gas pedal movement. Secondly, I would check the position of the floor mat and might even remove it, as well as check the gas pedal linkage under the dash and check for anything that can come into contact with the moving linkage. Did the mechanic check the engine mounts for movement? The rough running you mention is the rpm safety built into the computer to limit the engine speed in neutral and park.
Dear Doctor: I own a 2005 Mercury. Recently I was reviewing the manufacturer’s recommended maintenance schedule and these were the major items listed: motor oil & filter change, air & fuel filters, transmission fluid change and engine coolant flush & change. A brake fluid change, however, was not included. Why not? Is this something to be concerned about? Couldn’t moisture and contaminants accumulate in the brake system over time? A power steering fluid change also was not listed. Tony
Dear Tony: It’s great to see my readers are on the ball. A lot of manufacturers do not have the fluids you mention in the maintenance requirements. Brake fluid is wet, and yes, does attract moisture, and breaks down. Power steering fluid also wears down in protection and gets contaminated from normal wear. If you want to change either fluid yourself, get two turkey basters and mark them. One will be for the power steering fluid and the other for brake fluid. (Do not use either for any other fluid). You can siphon the fluids separately every two years and dispose of the fluid properly.
Dear Doctor: I own a 1972 Mercedes 280 SE. When I purchased the car the gauges worked fine for the fuel/oil/temp/battery. I decided to have the body repaired for rust on the running board and had the whole car painted. Now I notice the temperature gauge no longer works together with the power window. I brought it back to the shop and they were able to correct the power window. Unfortunately they were not able to figure out the temperature gauge problem. What is your advice? Jun
Dear Jun: We first have to make sure the engine is coming up to proper temperature. The temperature gauge will require a simple test starting at the temperature-sending switch on the engine. A good technician will be able to disconnect the sender switch wire and observe the gauge and touch the wire to ground and watch the gauge needle. As long as the gauge needle moves, you know the wiring to the gauge is good and the problem is just a sending switch.
Dear Doctor: Last November I had the fuel pump replaced in my 1995 Chevy Blazer by my repair shop. In February my fuel pump went again and was replaced by the same shop. Two weeks later I was driving on the highway and my car lost power. I started it up and it was fine for 5 miles of driving. I bought it back to the shop. They replaced everything from the computer to the distributor and coil. It isn’t costing me because the shop is working with me on finding this problem. I would appreciate your thoughts on this problem. John
Dear John: Before replacing any parts we need to make sure there are 12 volts and a good ground at the fuel pump. I’ve seen a lot of voltage drop problems on multiple fuel pump replacements, as well as a lot of wire corrosion. Have the technician start at the under-hood connections, usually on the driver’s side under the relay center. Next follow the wire down to the fuel pump, checking both sides of the wire disconnects. A dirty ground will cause this problem. Both Identifix and Alldata have wiring diagrams and step-by-step information for trouble shooting.

Junior Damato is an ASE-certified Master Technician.

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Copyright, Motor Matters, 2009