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Auto Doc: Start/stop ignitions are here to stay

Dear Doctor: I am interested in the 2015 Jeep Cherokee with the 3.2L V-6 engine. However, I am concerned about the new stop/start feature. What, if any, problems can you foresee occurring with this component? I am wondering what impact this will have on the battery life, as well as the ignition. 

Dear Elaine: The start/stop feature will be implemented into more vehicles in years to come. I recently spent a week in the new Jeep lineup, including the 2015 Cherokee. The start/stop technology is here to stay and I would not be worried about the start/stop feature at all. Battery life has increased over the years because of the design, larger size in most vehicles, faster, easier engine starting, higher rate charging alternators. For these, and other reasons, there is no need to worry about the start/stop feature.


Dear Doctor: I've had a strange issue with my 2006 Chevy TrailBlazer that has 134,000 and is well maintained, including a full tune-up at 100,000. When driving at 50 mph for more than 10 minutes at cruising speed the rpms start slightly bouncing and I notice a slight jerk. When I accelerate it shifts fine and stops jerking. No "check engine" light was on when it started doing it for first few months, but now I got a po171 system to lean bank 1 code. Is this related? 

Dear Mickey: The fault code p0171 indicates as lean condition (too much air, not enough fuel). When checking for any fault code the technician will use a specific professional scan tool (not OBD generic). Checking under vehicle specific testing will allow the scan tool to display all parameters when the fault code appeared, as well as oxygen sensor, mass air information and more. The hesitation can be related to the lean condition. If the fault is a dirty mass air flow, then a simple cleaning could fix the lean condition problem. Have an ASE-certified technician look on Identifix and Alldata web sites for known good sensor values to compare the actual vehicle values.


Dear Doctor: My wife drives a 2009 Toyota Camry and had been complaining about poor gas mileage. When we first got the car I did a mileage calculation at 10,000 miles and it was getting 30.4 mpg. It now has 45,000 miles and I did another calculation and it was down to 20.1 mpg. There is no "check engine" light and the car drives the way it always has. Any ideas? 

Dear Peter: Whenever I get a customer with a gas mileage complaint I perform a full vehicle evaluation, which includes the engine, transmission and braking systems. The next step is a check of the computer system and engine input sensor values. Sensors get lazy and do not respond as they did when new. A few things to look at are the air filter and inlet for restriction, correct spark plugs, and coolant sensor operation. The front and rear air ratio/oxygen both will also drop in mileage, as will a thermostat that does not allow the engine to reach full operating temperature.


Dear Doctor: I recently rebuilt the engine on my 1988 Corvette with 29,000 miles to factory specs. The mechanic had me "break in" the motor with standard motor oil. At 350 miles he had me change over to the factory recommended Mobil 1 synthetic oil. I've driven 300 miles and noticed the oil is about one-quarter quart low. Should I replace current synthetic? Is this normal oil consumption? 

Dear Anthony: Having a rebuilt engine is all together different from a new engine in a new car. The building specs are all together different than an old new rebuilt engine. At this point I would change back to regular petroleum oil and let the engine parts wear in. I would not change to full synthetic until 5,000 miles. If you want to change the oil at 1,000-mile intervals, then that's a good idea since you do not put a lot of miles on your car.


Dear Doctor: You've probably been asked this hundreds of times but this 2007 Honda Accord of mine has 112,000 miles. During my last oil change (with Sears) the mechanic talked me into using 5W20 synthetic oil. Is this a good time to do this type of change? I had a very bad experience with a 1977 Ford Granada back in the 1980s. Back then, I had the mechanic put Mobil 1 in the engine and I lost compression on two cylinders shortly after. What is your opinion on this matter?

Dear Herb: The oils and engines of 30 years ago are not the engines and oils of today. At this point in your mileage, changing over to synthetic oil should not cause any engine problems. The oil change mechanic should have suggested high-mileage synthetic oil, not just regular synthetic oil.

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