Q: Recently in helping my elderly father-in-law start his Lincoln, I came upon a quandary. When jump-starting a vehicle, I know that decades ago it used to be useful to run the RPM up in the vehicle providing the jump, thereby providing a higher voltage from the generator. In modern vehicles with alternators I know increased RPM doesn't equal higher voltage, but does it provide higher amperage? Does it do anything? Is it at all useful to rev the engine of the vehicle providing the jump?
A: The voltage output is actually regulated to a maximum of fewer than 15 volts. Voltage pushes the electricity through the wires while amperage is a measure of how much electricity is flowing. Using a garden hose for an analogy, voltage is the water pressure while amperage is how much water leaves the nozzle. Increasing the engine speed on the donor vehicle makes sure that enough amperage (current) flows to the weak battery. Yes, it is helpful to rev the engine and hold it around 1,200 RPM.
Q: I just drive a short distance every day. I had written you in the past and you told me to run the engine till it is completely warmed up. I have been starting my car every morning with the remote start and letting my car run for about 10 minutes, then drive my car to where I have to go. Lately I've been reading that warming up the car is bad for your engine because excess gas goes into the intake valves. What should I do?
G.D., Harleysville, Pa.
A: Since the advent of fuel injection, excess fuel use during warmup has not been an issue. When cars had carburetors, fuel enrichment choked an engine — it allowed too much gas to flow until the choke was opened. Fuel struck the intake valves, then washed past the piston rings and drained into the crankcase, where it diluted the oil. Today's computer controls lean out the fuel injection as the engine warms up. That is why remote starting is acceptable.
Q: I have a 2007 Ford 500 LTD with 30,000 miles that has provided great service since I purchased it new. Over the years my tires have had air loss, so to solve the problem the shop ground the corrosion off the mag wheels. Is it time for new rims? Do I need to get exact replacements or would a new or used rim of another metal be a reasonable substitute? I am not concerned that the car's appearance would change. It might be fun to have some "baby moon" hubcaps put on it like I had on my 1954 Dodge.
R.H. Crystal Lake, Ill.
A: As long as the corrosion is gone and the wheels are holding air, keep them. But if you need to get new rims, you can go with any that are the correct size and bolt pattern. Steel wheels, which may accept baby moon hubcaps, hold air more dependably and are less expensive than alloy wheels.
Bob Weber is a writer, mechanic and Master Automobile Technician.