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Dear Doctor: I have a 2007 GMC Envoy with 115,000 miles. The dash light – indicating code p0171 – comes on during long rides and sometimes goes out, but comes back on again with local driving. In the past two months, I have had multiple cylinder misfirings; I switched coils and it didn’t come back. I did a tune-up, cleaned the throttle, and changed the front oxygen sensor. Have you seen this before?
Jim
Dear Jim: It appears to be related to part throttle at cruising speed. The technician can connect a quality scan tool and go to freeze-frame memory to view all of the computer inputs to determine when the code was set and exactly what caused the code to trigger. Lazy oxygen sensors can always be a code setter, as well as dirty injectors and carbon deposits. The p0171 indicates a lean condition – too much air and not enough fuel. Low fuel pressure is rare on this vehicle. Ignition coils and worn spark plugs would cause a misfire, not the lean code. An exhaust restriction, such as a partly blocked catalytic converter is a common failure to cause multiple misfire codes.
Dear Doctor: I purchased a used 2005 Suzuki Forenza and installed a used radio, but now the back-lighting has stopped illuminating on the radio dials and I cannot see the station numbers. I sure do miss knowing what station the radio is on, as well as being able to see other settings. What is the problem?
Pete
Dear Pete: You must first check to make sure the light wire to the radio has power and is plugged in. Some radios have replaceable bulbs, others have diode-style lighting, while others have a circuit board that must be replaced by a professional. You can always buy another used radio or check with an electronics store for the price on a new aftermarket radio – and this may be your best bet.
Dear Doctor: I own a 2003 Chevy Malibu with 106,000 miles. Recently it developed a loud squeak from behind the back seat. It started shortly after we had rear struts installed at a retail tire chain. They checked the car and said that it wasn’t the struts. They gave the wheel wells and underside of the car a healthy dose of WD40 and the squeak stopped for awhile, but it has returned. My regular mechanic said it’s not from the interior or the wheels but thinks it is coming from the frame or floor pan but he wants nothing to do with finding it, saying that it could take many hours. Do you have any thoughts?
Bob
Dear Bob: It’s time to get to another shop and let them find the source of the squeak. The car will need to be checked on a drive-on-style lift that raises the car with all the weight on the wheels. The technician will bounce the car to locate the source of the squeak. If it is related to the rear strut replacement, then back to the shop you go with the bill you paid to pinpoint the squeak.
Dear Doctor: I own a 2003 Mercury Grand Marquis. Recently, it developed a problem with the sound of water sloshing back and forward when stopping or driving from a standing position. I have seen many garage mechanics who have checked drain hoses, checked heater cores, radiator, but cannot find the source of the sloshing sound. They have said not to worry; the sloshing will disappear on its own. The drain hoses have been checked for blockage, and all are okay. Can you help? Joe
Dear Joe: The first thing is to locate the source of the sound. I have seen some vehicles have movement in the heater hoses and heater core. In some cases, a small restriction in either of these hoses did eliminate the sound. For testing purposes, use a clamp-off tool to stop the coolant from flowing through the heater core. Water in the heater box can also be a culprit. Check to see if water is stuck in the front doors. Some doors have drains at the bottom.
Dear Doctor: I own a 2002 Pontiac Sunfire. The front lug nut studs keep breaking. The studs become brittle and fall off. I have them torqued to 100 PSI. Why are they breaking? Ned
Dear Ned: If wheel studs break off, then there is a wheel fit or contact problem. Wheel studs will break if the metal rim does not seat properly against the hub, or the lug nuts are not loading the wheel to the hub correctly.
– Junior Damato, Motor Matters
Copyright, Motor Matters, 2016
(Manufacturer photo: 2007 GMC Envoy)
Junior Damato is an ASE-certified Master Technician.
E-mail questions for publication to info@motormatters.biz
Mail questions to: Motor Matters, PO Box 3305, Wilmington, DE 19804