Q: I have a 1998 Jeep Grand Cherokee V-8 with 127,000 miles. My air conditioner smells when I run the unit. The smell goes away when adding refrigerant but comes back after a few weeks. I don’t want to replace the evaporator core — this is what may be the problem — as this would be too costly for a car of this age. I tried spraying air freshener into the unit but again, it only helped for a few weeks. Can I blow air through the vents with a pressure hose? What options do I have, as the car still runs fine?

A: Spring must be here — this is the first air conditioning question of the season. If the smell is caused by mold, mildew and debris in the evaporator, check the water drain at the bottom of the housing. If this is blocked, water builds up in the housing and promotes decay of organic debris and causes odors. If the drain is clear, try an air conditioner deodorizing spray available at auto parts stores. With the vehicle warmed up and the air conditioning running on high/recirculate, spray the deodorant down the fresh-air vents at the base of the windshield.

If all this fails, the entire system can be deodorized by professionals, even to the point of physically cleaning the evaporator and vents, and using a special ionization machine to remove odors.

I’m a bit concerned by the repeated adding of refrigerant. I’m OK with topping up the system as long as the refrigerant charge lasts the entire season. But if it doesn’t, the system needs repair.

Q: My ’93 Ford E250 has a 351 motor, runs well and has about 120,000 miles on it. However, it is very hard to start in damp weather after sitting overnight. The battery is good, it turns over OK and when the engine finally starts, it belches a little smoke. Once it warms up, it’s fine. When it’s cold outside, it starts just fine. Any ideas?

A: The most common cause of difficult starting in wet/damp weather is moisture penetrating some component in the secondary ignition system — module, hall effect sensor, coil, spark plugs, cap, rotor or spark plug wires.

If these components haven’t been checked or replaced, start there. But don’t overlook a faulty connection or sensors in the engine management system that could fool the electronic control module into thinking the engine needs more fuel at startup.

The simplest test is to check for spark at one of the spark plugs at your next overnight “damp” start. If there’s no spark, it’s something in the secondary ignition system. If there’s spark, it’s likely a sensor input to the ECM.

Q: I have a 1999 Honda Accord with 170,000 miles on it. My mechanic is saying to keep the engine running correctly it is a good practice to have the valves adjusted every 30,000 miles. Is this necessary? I have never had the valves adjusted. The engine runs fine, and I do not hear any clickety-clack associated with valves being out of adjustment.

A: According to the maintenance schedule listed in my ALLDATA automotive database for both 4-cylinder and V-6 engines, Honda suggests valve adjustment at 30,000-mile intervals “only if noisy.” Since the valves in your Honda aren’t clickety-clacking, I don’t think adjustment is necessary.

Speaking of valves, has the timing belt been replaced? Honda recommends 105,000-mile replacement intervals for both engines.