Q: My 2004 Lincoln Aviator hesitates when accelerating from about 40 mph. It has good power from a dead stop and gets up to speed quickly. It feels like the engine has enough power for all other operating conditions, just not when accelerating moderately from about 40 mph. I took it to a shop and they told me the fuel injectors should be cleaned at a cost of about $200. What do you think? -- J.F., New Lenox

A: J.F., that hesitation you’re referring to is likely due to be an ignition misfire and not the result of clogged fuel injectors. If the fuel injectors were partially clogged, you’d probably experience a rough idle and poor acceleration from all speeds. Since the problem is only evident when accelerating under light load, I suspect one or more ignition coil packs or spark plugs are at fault. Your Aviator’s engine uses a separate ignition coil on top of each spark plug. A problem with these ignition components can cause the symptoms you describe. Take your Lincoln to a repair facility that specializes in Engine Performance repairs for a proper diagnosis. I don’t believe cleaning the injectors will fix your woes.

Q: I own a 2006 Chrysler Town & Country minivan. With the heater control set for the floor, hot air comes out of the upper dash vents. You have to close the vents to keep heat out of your face. I took the van back to the dealer and they said this was normal. Any suggestions? -- J.R., Alsip

A: J.R., it doesn’t sound normal to me. Usually, when setting the control to “FLOOR”, it’s normal for a small amount of air to come from the defroster ducts, but not the ducts that aim at the driver and passenger’s face. Your Town & Country utilizes an electric actuator to control which direction the air blows. There could be a problem with this actuator or one of the mode doors. Take you minivan to another dealer for a second opinion. If after that, you’re still not satisfied, you may want to contact the manufacturer’s customer relations department at 1-800-992-1997.

Q: The tires on my car loose about 10psi air pressure each week in the cold weather. I was once told that my rims were leaking. Now I’m being told that I should have my tires inflated with Nitrogen instead and they won’t leak as much. What should I do? -- P.O., Chicago

A: P.O., while filling your tires with Nitrogen will result in more stable pressures, I’d recommend you first have your rim leaks taken care of. To do the job right, a technician will need to completely dismount the tire from the wheel so the wheel’s bead seat area can be thoroughly cleaned of debris. This usually requires the use of power tools. Once all the debris has been thoroughly cleaned from the rim, a sealant can be applied to the bead seat area to ensure there will be no more leaks. Then, you have a choice of filling the tires with compressed air (78% Nitrogen and 21% Oxygen) or compressed Nitrogen. I’d go with the Nitrogen if I were pumping up the tires on a racecar or airplane. But for all my street vehicles, I still rely on “free” compressed air.

AutoAdviser: Ira Siegel is an Automotive Instructor and ASE Certified Master Auto Technician. If you have auto-related questions for Ira Siegel you can call and leave your questions at the Auto Adviser Hotline at 708-633-6839 or e-mail a question to Autoadvisr@aol.com.