Q.  I recently bought a 2011 Honda Accord and I’m generally pleased with it. However, it rides like a truck. (My previous vehicle was a pick-up.) It has low-profile tires and I’m assuming that’s the problem. These tires don’t seem to absorb road shock the way that tires with a larger cross section do. I feel and hear every bump and irregularity in the road. Is my assumption correct, and if so, what can I do about it?

A.  You’re correct; it’s the combination of low-profile sport wheels and tires that causes this stiff ride. But this combination of wheels and tires also improves the car’s overall handling. You could try different size tires, but this will be expensive since you’ll be using trial and error to find the best ride.

Q.  My car stalls when the air conditioning is on. This doesn’t happen all the time, but it’s almost like a power surge takes over the engine. Also, when I turn the selector knob to the defroster position, the air conditioner comes on even when the A/C knob is off. What’s happening?

A.  Intermittent problems are the most difficult to diagnose. After checking for codes, I’d look at the various power and ground circuits for the computer. It’s possible that the additional electrical load of the air conditioner is causing an issue with the car’s computer that results in stalling. Regarding the defroster, many defroster systems turn on the air conditioner automatically to help reduce humidity in the car and better clear the windows. This may be normal.

Q.  I had tremendous shaking in my 1999 Mercedes-Benz C230 with sport wheels. I had new tires and wheels put on and things were great until I took it in for rotation. They tried four times to balance the tires and also checked the wheel alignment. The car still shakes, to the point that the tire store put brand-new tires on the car free of charge. Things are a lot better, though there’s still some shaking at 65-70-mph. I’ve spent more than two months looking for a solution. Any ideas?

A.  Since the vibration was gone after the first new tires were installed, that tells me the issue is related to the installation of the wheels and tires. The issue could be the hub-flange that the wheels mount up against. The technician should use a dial indicator and measure the run-out of the wheels and the flange area that the wheels mount against. It seems that at one point the wheels, tires and flanges lined up perfectly. Once the tires were rotated, the wheels were again miss-matched, causing the vibration.

Q.  I am considering buying a new Ford pick-up truck. I’ve seen the Eco-boost engines, but I’ve always driven a truck with a V-8. I’m replacing both an old truck and an old four-door sedan. What are your thoughts about Ford pick-ups, this new engine and replacing a car and a truck with just a truck?

A.  I haven’t driven the Ford F150 with the new engine, but I recently drove one with the 5.0-liter V-8. The ride was very smooth and comfortable, and this truck had all the creature comforts any driver could want. In my opinion, this is a vehicle you could drive every day and never miss having a sedan. The overall fuel economy with the V-8 was just short of 18 miles per gallon. With the twin-turbocharged V-6 making five more horsepower than the V-8 while delivering up to 20 percent better fuel economy, it’s easy to see how this engine has become such a popular choice and one you should consider.

Q.  I’m in the market for a rather expensive used (I mean, “pre-owned”) car. Do I need a CARFAX report?

A.  A CARFAX report can be a good investment. In fact, AAA Members get 15 percent off these vehicle-history reports (see the Automotive section of AAA.com for details). Also, Keith Griffin, editor of the used-car section on About.com, says you should consider a pre-purchase inspection by AIM Mobile Inspections (www.aimmobileinspections.com). This is a nationwide service that I’ve seen demonstrated and is quite impressive. In addition to the physical inspection, they road test the vehicle and examine all the vital fluids for contamination.