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Auto Doctor: Heater blows cold air

Owners of 2002 Jeep Grand Cherokees don't necessarily

Owners of 2002 Jeep Grand Cherokees don't necessarily have to remove the entire dash assembly to fix a heater that only blows cold air. Photo Credit: Chrysler Group LLC

Dear Doctor: I own a 2002 Jeep Grand Cherokee and the heater is only blowing cold air. The dealer said the problem was a broken blend door in the heater box. They said the whole dash assembly has to be removed to replace the broken plastic blend door. The repair estimate was $1,100 to $1,300. Are there any other choices? -- Gerald

Dear Gerald: I see a lot of Jeep and Dodge trucks with these problems. Yes, there is an alternative to the $1,000-plus repair. We use a company called Heater Treater. With this product the dash does not have to come out. Most of the repairs can be done through the removal of the glove box and using a dremel tool to open up the heater box, remove the broken door and replace it with the redesigned door. This works on both single and dual temperature systems. The company also has repairs for Ford heater box door failure.

Dear Doctor: I own a 2001 Toyota Camry four-cylinder with 134,000 miles and a "check engine" light. The shop scanned the computer and retrieved codes p0420 and p0446. The technician said these are very common codes found in Toyota vehicles and that the cost of repairs would be up to $1,500 for a catalytic converter and charcoal canister with needed valves. I went to the dealer and they said the cost would be even higher. What should I do? -- Cindy

Dear Cindy: The most common problems I see are catalytic converters, evaporative charcoal canisters and attached valves, air ratio sensors, mass air flow meters and coolant temperature sensors. The cost for your repair is fair. Toyota is not alone with emission part problems. All manufacturers have emission parts that fail and some are more expensive to repair than others.

Dear Doctor: I have a 1998 Ford Ranger with a four-cylinder engine (99,333 miles) with a vibration problem, more so when it's idling in gear. It's like riding in a blender. My mechanic increased the idle speed which helped, but when I'm stopped at a light, it's always straining to go. I don't think that's good for the transmission. Is there something that can be done to quiet this baby down? -- Ralph

Dear Ralph: The four-cylinder engine will have some minor vibration. When we get a vibration complaint we inspect engine mounts, exhaust system and hangers. We also have someone sit inside the vehicle with the engine in gear while the vehicle is vibrating. Next, we use a large pry bar and lift on the engine one side at a time and see if there is any change. We also remove the fan belt or belts and restart the engine and see if the vibration changes. This is what needs to be done -- as long as the engine is not skipping or running rough at idle.

Dear Doctor: I have a 2010 Ford F-150 with the 4.6-liter engine. I notice when the truck starts in the morning there's a puff of blue smoke and then it disappears. I have been to Ford, but they were unable to find the problem. Do you have any suggestions? -- Robert

Dear Robert: The most common cause of blue smoke after an engine has sat for 8-plus hours indicates oil has leaked down into the cylinders from the valve guides and/or seals. This will not cause any long term engine failures. You did not mention how much oil the truck goes through. A quart of oil per 1,000 miles is not unusual.
  -- Junior Damato, Motor Matters

Junior Damato is an ASE-certified Master Technician. Email questions to

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