Dear Doctor: I have a 2007 Chevrolet Impala with automatic headlights. Two months ago, the bright high-beam headlights started going on by themselves and remaining on, until I move or tap the turn signal stalk fore/aft to turn them off. They usually go right back on. Sometimes they stay off for 20 minutes. I took out the fuses for the high beams. Did you ever hear about this problem? -- Bruce
Dear Bruce: The most common problem is the steering column switch. I followed the wire diagram on our Identifix web site and found that the high-beam lights get energized when the lever is moved. Then from the lever movement the signal goes to the body control module to the high-beam relay and out to the headlights. I would check both the steering column switch and the relay.
Dear Doctor: I am the original owner of a 2001 GMC 3500 dually pickup truck. It has always had a very low brake pedal. I notice that when I back up and hit the brakes to loosen a load that I get a firm high pedal for the next few days. Any ideas on how I can keep that pedal longer? -- Tim
Dear Tim: There has been a lot of talk over the years on upgrading the brake rotor size with aftermarket brake rotors and calipers. In some vehicles, replacing the single diaphragm vacuum brake booster (if equipped) to a dual diaphragm will help. You have to make sure that all the caliper slides move freely and also to bleed the system. There is also a pedal adjustment at the brake pedal rod on most vehicles as well as another rod adjustment between the master cylinder and vacuum brake booster, if equipped. I have found that semi-metallic brake material works best in trucks and offers the most amount of resistance when stopping.
Dear Doctor: I have a 2002 GMC Denali. When I allow the engine to warm up in the morning and then go into drive the idle goes high and it won't kick down. I have to shut it off, wait, and then it appears to be okay. What is the problem? -- Karen
Dear Karen: A vehicle's idle speed, as well as other systems, is computer-controlled. Most newer vehicles have the drive-by-wire, which means there is no mechanical connection between the engine and the gas pedal. When you press on the accelerator you are sending a voltage signal to the computer and then to the electric throttle body motor. To check these systems a qualified technician will use a professional scan tool -- not a code reader -- and monitor the system. It sounds like there could be a problem in the idle motor and/or circuit.
Dear Doctor: I have a 1997 Dodge Grand Caravan with a 3.3 engine. One day it stopped running while I was driving it. It has been looked at by at least four different people. Still not running. The crank and cam sensors have been changed and I also put in a computer that I picked up on eBay. Still didn't help. The last time I looked at it there was no constant spark at the plugs. It seems to spark for about a second and then looses it. Any input would be great. -- Ron
Dear Ron: I see many vehicles every week with a lot of new parts installed yet the engine still does not run. On most late vehicles you cannot just put in a computer and or body control module. Every vehicle computer has the vehicle identification number programmed into it. The next step in this mess is a trip to the dealer and/or a shop with ASE technicians. Make sure you bring the original computer with you. The first thing the technician will do is put the original computer back in the vehicle and try to start the engine, observing all data and checking for trouble fault codes. The problem could be as minor as a poor connection, especially at the fuse box by the battery.
Dear Doctor: I recently saw an ad for the Buick Encore with AWD and would like your opinion on it. -- Ernie
Dear Ernie: I spent a week in the Encore AWD Premium model. The rear seat area is a bit tight, but take into consideration this is a downsize SUV. A powerful 1.4-liter turbocharged four-cylinder via a 6-speed automatic delivers plenty of power and gas mileage. Front seating is firm and comfortable. This Korean-built General Motors vehicle has everything going for it at 23 mpg city 30 mpg highway and was a joy to drive. -- Junior Damato, Motor Matters
Junior Damato is an ASE-certified Master Technician. Email questions to firstname.lastname@example.org. Mail questions to: Auto Doctor, 3 Court Circle, Lakeville, MA 02347