strong>Dear Doctor: I bought my 2012 Toyota Corolla used with 20,000 miles on it; it now has 88,000 miles. When I start it in the morning, the engine squeals very loudly and then the noise eventually stops. Even during the day after it sits a couple of hours it will still squeal for a while. This has been happening for the last six months. I tried turning the ignition key slower than I normally do thinking the computer needs more time to start things moving but it still happens. Marcia
strong>Dear Marcia: A squealing sound when started is usually caused from a loose or worn alternator belt. In some rare cases, the power steering or air conditioner belt could also be the fault. Most late-model vehicles have an automatic belt tensioner that ensures the correct tension. The sound has nothing to do with the key turning or computer. Do not use a cheap off-brand belt for replacement.
strong>Dear Doctor: When I picked up my 2016 Volvo XC90 after its 20,000-mile/2-year service maintenance, the service manager informed me that they do not rotate the tires, not even front-to-back. This directive comes from Volvo. The floor-mounted laser tire tread measurer says that I have 5/32-inch on both front and 8/32-inch on both rear tires. These are expensive low-profile Pirelli tires and I don't believe I'm going to get my fair wear out of the tires with this policy. What is your opinion and/or experience? Bill
strong>Dear Bill: There are a few vehicles that the tires cannot be rotated because of the size difference front-and-rear. I rotate tires on an annual basis on vehicles that do have the same rim and tire size. I rotate the tires if the tire and rim are the same size and keep the tires on the same side of the vehicle.
strong>Dear Doctor: I own two Hemi-powered vehicles. The first is a 2015 Dodge Ram 1500 crew cab and the second is a Jeep Grand Cherokee Limited. They perform very differently and I've been looking into doing some modifications to the Ram. The Grand Cherokee runs and shifts smoothly in all driving situations. Let me tell you, when you put it in Sport mode it becomes a respectable performance vehicle! The Ram truck, on the other hand, tends to stumble a little when you hit the gas quickly. I always run them on premium fuel but I've been told by mechanics I'm wasting my money because these engines are programmed for 89 octane. Do you agree? The Ram gets about 5 mpg less than the Jeep when driven the same and I've been looking for ways to increase the fuel economy. Would headers help with increasing fuel economy? I've also noticed when the truck goes into Eco mode it tends perform poorly. I'd also like to know: Should I reprogram the ECM? Rob
strong>Dear Rob: These vehicles have the same base engine, and that's all they have in common. The engines are tuned differently via the computer, as are the transmissions and the actual gear ratios are different, not to mention the weight of the pickup, and larger tires that have more rolling resistance than the Jeep. As for the use of premium gasoline, it burns slower, cleaner and hotter than regular 87-octane gasoline, not to mention leaving fewer deposits on the piston and valves. Now for modifications, I install a lot of cold fresh air intake systems. They are simple to install and let a lot more air into the engine. The exhaust system is very large and has good exhaust flow as is. Any replacement would be a lot louder with little or no benefit beyond the unwanted noise. A computer programmer would be good to wake up the engine and transmission. Most programmers have multiple setting options and you can make a change as often as you like to eco, performance, or towing mode and back to stock. You will feel a difference.
strong>Dear Doctor: I have a 2014 GMC Sierra with the 5.3-liter engine, 6L80 transmission, and 53,000 miles on the odometer. Sometimes, when I shift from park to drive, it exhibits a slight delay to engage into gear. It doesn't matter whether the engine is hot or cold. It is most noticeable when stuck in a fast food drive-through. Any ideas on the problem? The transmission fluid level is OK. It is still under warranty but since it is intermittent it is hard to diagnose. Any ideas based on your experience of the problem? Tom
strong>Dear Tom: The intermittent slight delays on any automatic transmission are usually caused from internal line pressure in the transmission. This can be the angle the transmission gear / clutch packs are in, or even the position of the torque converter. I do not see this as a problem. The 6L80 transmission is a heavy-duty transmission and used in a lot of high-horsepower race street cars.
strong>Dear Doctor: I read that Jeep is having a banner 2018 in vehicle sales. I hear a lot of buzz about the new Trackhawk. What can you tell me about it? Nick
strong>Dear Nick: The Grand Cherokee has been around for many years. I remember when then Grand Cherokee was a bulky hard-riding, poor-handling vehicle. Today's entire Jeep line up has something for everyone. I drove the Grand Cherokee Trackhawk, which is outfitted with the 707 horsepower Hellcat Hemi engine, heavy-duty eight-speed automatic, as well as a heavy-duty AWD system. Brembo brakes, specially tuned suspension, big 20-inch alloy wheels and performance tires, and large free-flowing exhaust round out the package. If you want to drive the Trackhawk like a sports car, turn the consul knob to sporty or track mode. Its many performance settings modify shift points and launch control (which helps when leaving the starting line to prevent spinning the tires).
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