Q: I have a 2007 Hyundai Entourage that failed the emissions test. I couldn't believe it as the minivan is regularly maintained. They told me I had to drive it more and then come back. I couldn't believe it, so that same day I went to another facility and the results were the same! After calling our dealer service department, he said the same thing: Just take it on the highway for a long drive. I had my daughter take it on a road trip and lo and behold, it passed. What gives? They're trying to control emissions but want us to drive and pollute more? I think it's nuts, what about you?

J.S., Chicago

A: It is not nuts, but simply nuts-and-bolts when it comes to emissions testing — especially if you had work done on your car. After some repairs, the engine control module (ECM) will monitor whether everything is in compliance. Some things need to be cleared by driving the vehicle until that happens. Driving the car in all modes — city, highway, stop-and-go, etc. — will clear the monitors. For instance, if you never drive on the highway, the monitors will never be cleared. Thank your daughter.

Q: It looks like the starter ring gear on my 2004 Camry is going bad. Replacing the starter didn't help. Is there an easy way fix to this problem? Do I have to pull the motor out? Is this a costly job? Is there a way to reposition the ring gear?

V.G., Skokie, Ill.

A: The ring gear is attached to the torque converter, which acts like a clutch between the transmission and engine. The starter gear engages the ring gear, which then spins the engine to get it running. In order to replace the ring gear, the transmission must be removed. In order to remove the transmission, which is attached to the engine, both parts must be removed as one. Yeah, it is going to cost you. The ring gear cannot be repositioned.

Q: We bought a certified pre-owned 2016 Audi last April. During the summer most times when the air conditioner was turned on, it would smell like vinegar. I contacted the dealer and was told that the condensation catcher would need to be drained. They said it is not covered by the warranty and costs about $150. I am curious about this. I never had this problem in any of my previous cars. They might have had an odor at first, but never vinegar and not almost every time it was turned on. I also thought it might be the cabin filter, but now I am just confused and hoping you could help.

D.S., Morton Grove, Ill.

A: Condensation forms in the HVAC (heating/ventilation/air conditioning) housing. There is a drain that allows the water to escape under the car. That is what you see on the ground when you park your car after running the air conditioner. If the drain is clogged, water builds up. In this dark, damp environment micro-organisms grow and make a stink. Bad stuff doesn't grow much in cold weather. A cabin air filter, especially one containing activated charcoal, may help, but the cure is to have the drain cleaned or repaired. By the way, if something was recently repaired using RTV silicone sealant, it emits a vinegar odor as it cures.

Bob Weber is a writer, mechanic and ASE-certified Master Automobile Technician.