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Service Engine Light: Check All Vital Signs

By Junior Damato, December 19th, 2015

strong>Dear Doctor: I have a 2004 Nissan Xterra and my "service engine" light is on. The scanner says #2 cylinder misfires and is running rough. I changed all of the wires, checked the coil and changed the fuel injector for that cylinder. What am I missing? Giuseppe

Manufacturer photo: 2004 Nissan Xterra
Manufacturer photo: 2004 Nissan Xterra

strong>Dear Giuseppe: The first step is to check all of the vital signs; look for a vacuum leak, especially at the hoses that are around the cylinder in question. Next, do a simple compression test. If compression is good, then check the fuel delivery, including injector pulse time on. The computer is in charge of the on/off time of the fuel injector and each injector has its own circuit. Also, there could be a mechanical problem that is causing the "service engine" light to remain on.

strong>Dear Doctor: I have a 1999 Nissan Altima with 51,000 miles with an intermittent problem. When braking to stop after driving at 30 or 40 mph, the engine does not begin to slow down, but rather it keeps racing for a few seconds and fighting against the braking before it stops racing and slows down to slow idle. The gas pedal has been checked and is not sticking. The brakes are fine. Sometimes I have to floor the brake before the engine suddenly slows to idle and the car stops. Can you help? Norman

strong>Dear Norman: This is a very dangerous condition and needs to be checked by a qualified ASE-certified technician. I would look at the idle air control motor, as well as the throttle body for carbon buildup. On some vehicles the idle motor is part of the throttle body and is expensive to repair. If the transmission has a pressure cable connected to the throttle body, then make sure it does not bind up. A throttle body replacement is cheaper than a new car.

strong>Dear Doctor: I own a 2001 Toyota Corolla. After sitting for a long period of time the car starts well without issues, but it drives for only a few miles and then stops. I turn off the engine and restart and it drives fine. My mechanic said nothing is wrong, but it might be bad gas and that I should always fire it up whenever that happens to improve gas circulation. Please advise. Chichi

strong>Dear Chichi: Bad gas? No. It may be time to find an ASE-certified technician who is knowledgeable and has access to Alldata and Identifix. I would take a close look at the throttle body for carbon buildup. I have also seen this same stalling problem after a simple battery replacement or if the battery went dead. To properly clean the throttle body it would have to be removed and cleaned by a qualified expert.

strong>Dear Doctor: I have a 2010 Toyota Avalon with 45,400 miles. It did not come with a compass on the rearview mirror or a GPS system. My children have offered to have both items installed by an accessory installation center. Would this cause harm to my car in any way? I am 82 years old and the only driver of the car. Vicky

strong>Dear Vicky: Aftermarket products, such as a GPS system and mirror compass, and backup cameras are all great if you have a need for them. I see no disadvantage to you or your car by getting this equipment installed. It will make the kids happy to spoil you.

strong>Dear Doctor: I like the ease of use with liquid car waxes, but I'm wondering how much protection the liquid version offers over the paste. What kind of car wax do you recommend? John

strong>Dear John: There are many brands of wax and combination cleaner/wax products. I have used them all. They all have different feels and their own secret formulas. Any of the top brand names, such as Mothers, Meguiars, Turtle Wax Ice, are easy to apply and remove. I personally like the paste wax over the liquid.

Big Drop in Fuel Mileage: Get Engine Test

10/19

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

10/12

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

10/05

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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