Q: I read your article on the ignition problems of a 2008 GMC Canyon with the 3.7-liter motor. I have the 2010 model with the same engine and had the same no-start issue. After a couple of warranty visits, the dealer asked to keep the truck for tests. The ignition lock change didn’t solve the issue. What apparently worked was that the mechanic located, disconnected and cleaned all the ground points he could find based on the schematics for the model year. I still have the truck 115,250 miles later; so far, no issues with the ignition.
R.H. Toano, Virginia
A: You found an excellent technician. Very few will spend the time to be so thorough. Chasing ground connections is like a dog chasing its tail.
Q: I have a 2006 Chevy Trail Blazer with 155,000 miles and runs great. My problem is that, for the past year, the vehicle will sometimes fail to start after being driven. I have had numerous parts replaced (fuel pump, mass air flow sensor, spark plugs, ignition switch, etc.) and the starting problem continues. The failure to start only occurs when the vehicle has been driven and then parked such as when going to the grocery store. If I then wait 30 to 45 minutes, the vehicle will restart. Any thoughts on a potential cause?
P.G., Virginia Beach, Virginia
A: If the engine does not crank, the problem probably lies with the starter. One trick I have used over the years is to tap the starter with something such as a tool or small hammer. If that gets you going, go to your favorite shop for a replacement. If it cranks but does not start, the problem is something else.
Q: I recently purchased a car in Arizona. They added a charge for nitrogen in the tires that included lifetime fills. Is this something necessary in the hot climates or just a scam? I am going with a scam.
R.G., Cave Creek, Arizona
A: I would not call a $10 to $15 per-tire charge a scam, but the customer should be told of the option upfront. Free lifetime inflation fills seems silly if nitrogen is unlikely to escape. There is an argument that nitrogen molecules are less likely to pass through the rubber than plain air. Plain air is, however, roughly 80 percent nitrogen. Go figure. I use air and have never had an issue. Of course, it is rare to find free air nowadays. Gas stations may no longer have pay toilets, but they do have pay air compressors.
Q: Your reply to J. & G.J. regarding high octane was spot on, but additionally, use of low octane fuel in a high compression engine will likely cause engine knock just as you said, which should be detected by the engine’s knock sensor. Thus (if all systems are working), ignition timing will be hindered and performance and economy will be reduced.
M.B., Chicago
A: Your reply to my reply is spot on. At the first sign of engine knock, the sensor will send a signal to the powertrain control module, which will then incrementally back off the ignition timing until the sound stops. So, if you expect top performance from a turbocharged or high-performance engine, you are encouraged to use premium, high-octane fuel.
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