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Auto Doctor: Flex fuel shouldn't pose any long-term issues

In cars whose engines are designed for flex

In cars whose engines are designed for flex fuel, such as the 2013 GMC Sierra HD, the computer, sensors and fuel injectors are multi-functional as well. Therefore, there shouldn't be any long term effects from using either and/or switching back and forth. Credit: General Motors

Dear Doctor: I have a 2004 Cadillac CTS with 80,000 miles. It's using 1 quart of oil at 300 miles. My mechanic checked it, including a compression test. There's no black smoke from the exhaust and he said he couldn't find anything wrong. What do you think? -- John

Dear John: That's a lot of oil consumption in 300 miles. Your mechanic will need to check the PCV system if equipped and make sure the crank case is not building up pressure. The engine does not necessarily have to have a compression loss to be consuming oil. Leaking valve guides will cause oil to be sucked into the cylinders and burn. There's also the possibility that the cylinder rings could be loaded with carbon and sludge, causing pressure in the crank case and oil consumption. GM sells a top engine cleaner that can be poured into each cylinder, and in some cases, break up the sludge and free up the piston rings. As for smoke out the exhaust, the catalytic converter is helping to burn up the oil, so you will not see it burning.

Dear Doctor: I have an intermittent problem on my 2009 Dodge Journey. When turning the key to start I get a clicking sound. After a few times it starts. The dead battery had to be replaced last week, and since then it has happened once again. The alarm goes off at odd times when unlocking the doors. Hope you have a solution. -- Bill

Dear Bill: The most common fault that causes a clicking is a faulty starter motor. It would be great if the clicking would happen at the shop so they can check for voltage at the starter motor. As for the alarm sounding, it could be the body control module getting confused and sounding the alarm. You can disconnect the battery overnight to completely clear the module memory.

Dear Doctor: I purchased a 2013 GMC Sierra 1500 pickup with the max trailering package and the 6.2-liter engine. After the initial break-in of 500 miles, I switched to flex fuel. The truck runs and drives fine on it and GM highly recommends the use of flex fuel. I plan to continue the using it when I'm not towing my camper trailer. My concern is the long term effects of flex fuel, even though the truck is designed and built for its use. What's your opinion? -- Denny

Dear Denny: There's no question that engines are designed for flex fuel and the computer, sensors and fuel injectors are multi-functional as well. I do not see any long term effects from using either and/or switching back and forth.

Dear Doctor: What can cause my 1991 Ford Explorer's steering wheel to harden while driving, but loosen up while pressing the gas pedal? Once I let my foot off the pedal it hardens up a little bit and then when pressing the brake pedal it hardens up again, like the vehicle had turned off. -- Javier

Dear Javier: There is no question there is a pressure problem. Most commonly the problem is the power steering pump. Before replacing the pump, have the front end checked for any binding or tight moving front end parts.

Dear Doctor: I've been dealing with an intermittent failure on my 2004 Chevy Impala. The car fails to turn over. At first the failures were months apart, but now they are more frequent. I'm sure the problem is with the security system. Can you help? -- Jim

Dear Jim: The technician will connect a professional scan tool and look for any stored fault codes in the body control module. There have been many ignition switch problems with these vehicles. Sometimes using a different key can make a difference. When the engine does not start try leaving the key in the "on" position for 10 minutes and look to see if the security light is flashing. If the light is flashing, then there is a fault in the security system that will require diagnostics and repair by a technician who has knowledge of the system.

Dear Doctor: I always carry jumper cables in case of an emergency. Lately, I've been hearing it's not a good idea to jump start a car today, even if connected properly. The possibility exists that you can burn out your computer in the donor car. I was told to buy a portable battery jump start. Any truth to any of this? -- Joan

Dear Joan: You must be very careful when jump starting a vehicle that has a dead or low battery. Damage to the computer and/or electronic modules is possible. Check the owners manual for specific information regarding jump starting. We always use a battery jump box when we get a vehicle with a dead battery towed to my shop. I would much rather see you with a battery jump box vs. using another vehicle to do jump start.

Junior Damato is an ASE-certified Master Technician. Email questions to Mail questions to: Auto Doctor, 3 Court Circle, Lakeville, MA 02347

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