Niagara Gazette

February 28, 2013

TOM'S CORNER: Colder weather affects gas mileage

By Tom Torbjornsen
Niagara Gazette

Niagara Gazette — EDITOR’S NOTE: The Gazette has partnered with local automotive expert Tom Torbjornsen to publish his weekly national column. Tom’s Corner will appear in Thursday’s editions. Today’s edition features reader questions and answers.

DON FROM MEMPHIS: I own a ‘07 Honda Accord Hybrid. I’m very pleased with the overall performance of the car, but I am disappointed with poor gas mileage in colder weather. I’m maintaining proper tire pressure. I assume it has something to do with dense air. Can you give me some guidance?

TOM: Don, It has everything to do with the colder temperatures and nothing to do with “dense air.” The performance system senses when the coolant is cold due to colder ambient temps, so it richens the fuel mixture which is necessary to start a cold engine. The fuel mixture stays rich until the engine reaches operating temperature. At this point, the fuel mixture levels out to a normal, leaner mixture for operating temps. Have a scan done of the system to make sure there are no codes. However, I think you’ll find that lower gas mileage is due to the colder weather.

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TIM FROM JAMESTOWN: I am experiencing ignition switch difficulties with my Saturn Ion 3. The service engine light flashes, all mechanical engine lights on the dashboard light up, and the car won’t start. After a while, it starts again with no problem. Occasionally, after locking the doors, the horn sounds. I am told that this is a ‘stall code’ and that the ignition switch may have to be replaced. Any advice? Is there a recall for this problem?

TOM: Tim, there is no such thing as a “stall code.” I checked and there are no recalls on your vehicle for this problem. The diagnostic procedure involves scanning the computer for trouble codes and then running the proper pinpoint tests necessary to track down the defective part. Is the ignition switch bad? Possibly, but the cost of diagnosing the problem is cheaper than replacing parts hoping to hit on the right one. The horn going off occasionally when locking the vehicle could be an indication that the alarm system is malfunctioning, so have this checked out. Success to you.

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LYNN FROM ALBION, MI: I own a ‘98 Pontiac 2.4L with a severe coolant leak on the right side of the motor towards the front. What is the source of this leak?

TOM: Lynn, without proper cooling system diagnostics it is impossible to answer your question. A cooling system pressure test will help to pinpoint the source of the coolant leak. It could be a hose or head gasket. Sometimes the source of a coolant leak is hard to find and a coolant dye test is necessary to track it down. A fluorescent dye is added to the coolant and then a fluorescent light (black light) is shown on the engine. The coolant becomes visible (a bright yellow color) under the light so you can identify the source of the leak. If I had to guess as to what the leak was I would say the head gasket. But have it checked out. Good luck.

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PETE FROM LUBBOCK, TEXAS: I own a ‘02 Neon. First the vacuum pump was replaced because the gas cap was not on right. Then the gas cap was replaced; then a vacuum hose between the air intake and the engine was repaired. However, the car still idles! At first it was a high idle. Now it is up and down like a washing machine. Can my mechanics be missing something? The car has over 100,000 miles.

TOM: Pete, vacuum pump? Gas cap replaced? What are you talking about? Have your tech scan the system for codes. It sounds like the IAC motor is acting up or the car could have a vacuum leak at the intake manifold. Now I hope you are not going to go out and replace the parts that I just mentioned without testing. If you do, I can’t say I didn’t try, but it’s your money! Good luck.

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RALPH FROM WEST HEMPSTEAD: I own a ‘06 Hyundai Elantra with very low mileage. I heard a noise when backing up, and found out I had to change all the brake pads and reface all four rotors. Is there anything I could do to have Hyundai bare the cost?

TOM: Ralph, Hyundai will not help with this cost because brakes are considered a wearable item. Brakes are expected to wear out and therefore not covered under warranty. There is one exception … if the brakes wear out due to a faulty part like a master cylinder or pressure equalization valve, which IS covered under warranty. In the case of such a part failing, then the brake pads may be affected as a result and thus covered under the warranty.

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LAUREN FROM OIL CITY, PA: I have a problem with my ‘96 Dodge Caravan. The vehicle acts as if it has run out of fuel. When this happens, I have to pull over and shut it down for about 10-15 minutes. Then I am on my way again. I had the fuel filter replaced after the first incident, but it keeps happening. After several more incidents, I had the fuel pump and ignition module replaced, but it still happens. However, I’ve discovered a pattern that may help diagnose the problem. This problem usually occurs when it’s very cold outside, after driving a certain distance (about 30 miles), and when the gas tank is down to between half and three quarters full. Lately, I have been filling up when the tank is down to three quarters. Could there be water in the gas tank (I’ve added dry gas several times)? Could it possibly be the type of gas I use?

TOM: Lauren, if I were pressed to describe your diagnostic technique in a phrase, I would describe it as “Squirrel Automotive Diagnostic Technique” because you seem to flit to and fro without rhyme or reason, replacing parts and coming up with new diagnostic scenarios. Based on what? Moon phase? Dreams? Drivability problems like you are describing can only be diagnosed one way ... by a computer scan of the system. In addition, you might want to have a flight test performed so the tech can see exactly what is going on at the time of the failure. Finally, a fuel delivery analysis is in order as well, to make sure there is no drop in fuel pressure. This is the most efficient and effective way to accurately pinpoint the problem. To indiscriminately replace parts hoping to fix the problem is a waste of time and money. I wish you success.

‘Til next time … Keep rollin.’

"America's Car Show" with Tom Torbjornsen airs 7:30 p.m. Wednesday, 9 a.m. Thursday and 11 a.m. Saturday on WBBZ-TV.