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What is Causing My Car's Dead Battery?

By Junior Damato, August 18th, 2018

strong>Dear Doctor: After driving a short distance in my 2009 Lexus, I stopped for 30 minutes of shopping and when I returned the battery was dead. I got a boost and the car started immediately. A mechanic told me I'm not driving enough to keep the battery fully charged. Is he right? What can I do to stop this from happening again? Gary

Manufacturer photo: 2009 Lexus IS
Manufacturer photo: 2009 Lexus IS

strong>Dear Gary: A full-system electrical check has to be performed on your vehicle, starting with the battery. To check the current voltage, a two-hour battery charge may be needed, followed by a battery load test. Next, the alternator needs to be checked for output. If the battery is faulty, then a good replacement battery with the highest available Cold Cranking Amperage is recommended. If the alternator is not good, then use a good brand, such as Denso or Bosch. Driving short distances on any late model vehicle will run the battery voltage down. A small battery maintenance charger is a good idea. A weekly 30-minute highway drive at continuous sustained speeds would also help charge up the battery. Remember, all late model vehicles have computers, clocks, and many power accessories that draw power when the key is off. You should also never leave the key fob in the car when parked. The key fob and push-to-start system are always communicating when the key fob is in range.

strong>Dear Doctor: My wife and I own a 2009 Jeep Patriot 2WD. I'm a retired auto mechanic and have been doing all of the regular fluid changes. The Patriot only has 37,289 miles and the body is in showroom condition, but we are undecided on how long to keep it. What should we be taking into consideration when deciding to keep or sell a vehicle? George

strong>Dear George: With such low mileage this Jeep is very desirable for a healthy trade value. There is no reason to trade or sell the vehicle, unless you want to replace it, or unless the Jeep has rust under the body, such as with the brake, fuel lines, transmission, oil pan and suspension.

strong>Dear Doctor: I own a 2004 Acura TL with 150,000 miles. It has never given me problems, but seems to have a fan issue. When I have either the A/C or heater blowing the fan sometimes shuts off and then comes back on. Other times I have to shut off everything and turn it back on. When I'm in stop-and-go traffic it seldom comes back on. My mechanic changed the blower motor, but nothing has changed. What should be done next? Peter

strong>Dear Peter: Before replacing the blower motor a technician should do a wiggle test on wires leading to the blower motor and on the blower motor itself. There is also a blower speed resistor inline with the blower motor that is known to fail, along with the terminal connectors. With some intermittent faults, we'll connect a small light at the blower motor terminals to determine whether power is getting to it.

strong>Dear Doctor: I own a 1993 Ford SHO with a 3.2 automatic with 147,000 miles. I have been using Motorcraft 5w30 synthetic-blend oil. But recently my local dealer changed the oil with 5w20 full-synthetic oil. They told me Ford said it was OK to use it. Is it advisable to with full-synthetic oil on this car? Also, the 1993 Ford SHO calls for premium fuel, but several years ago a bulletin came out to use 89 octane because of dieseling. My car at times seems to be out of timing in a hot restart. What are your thoughts? Ed

strong>Dear Ed: I agree with the dealer on the recommended use of full-synthetic oil, which is always a good choice. The use of 89 octane vs higher octane is the opposite of the dieseling. In the old days in order to help stop dieseling, the use of premium would help. Today, on fuel-injected vehicles when the key is shut off the fuel injectors stop squeaking fuel, unlike engines with carburetors where fuel would come from the carburetor as long as there was suction in the engine. As for the engine sounding out of time, the Ford SHO has a very special engine that should be checked by a qualified technician who is familiar with this engine.

strong>Dear Doctor: I have a 2014 Chevrolet Camaro SS with a 6.2-liter V8 and six-speed standard. The owner's manual recommends 91-octane fuel, and says the engine will also burn regular grade, but be cautious of pre-ignition. With rising gas prices, some people have suggested it would be cheaper to use regular, along with an octane booster. I don't want to damage the engine. Any thoughts? Glenn

strong>Dear Glenn: You own a vehicle with a high compression V8 engine the deserves premium unleaded fuel. The higher grade gasoline burns slower and cleaner, leaving less harmful deposits. Yes, premium gasoline has gone up a few cents. Could you give up buying a coffee or beverage once a week? This could pay the fuel price difference. As for octane booster, a good quality octane brand will cost $8 to $10.

Big Drop in Fuel Mileage: Get Engine Test


Big Drop in Fuel Mileage: Get Engine Test

strong>Dear Doctor: I have a 2014 Ford F-150 with the EcoBoost engine. The dealership cannot tell me why my gas mileage is at 9 mpg. It was 24 mpg when I purchased it. Can you help me out? Gerald

Gas Mileage Misread: Fuel System Needs Attention


Gas Mileage Misread: Fuel System Needs Attention

strong>Dear Doctor: I own a 2006 Ram 2500. The mileage calculator says I'm getting 30 miles per gallon in fuel economy, but I'm actually getting about 20 mpg. What should I do? Mark

Car Shakes at Idle: Check for Multiple Fault Codes


Car Shakes at Idle: Check for Multiple Fault Codes

strong>Dear Doctor: My 2009 Toyota Camry with 199,600 miles has a check engine light showing the codes P0101 and P0170. I have already replaced the MAF sensor, PCV valve, throttle body, the car's computer, O2 sensors, cam sensor, crank sensor, fuel pump, injectors, and fuel pressure regulator. I also checked for multiple vacuum or air leaks, and the cabin air filter, spark plugs, alternator, and battery have all been checked over the course of a year. Now the car has both codes showing consistently and it shakes at idle. What should we do? Cheyenne

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