If high-octane gas doesn’t fix spark knock, what will?
Q: I have a 2015 Chevy Colorado 3.6-liter V-6 with 45,000 miles that is serviced regularly and uses strictly Top Tier regular gas. When accelerating through second and third gears I regularly experience “plug knock,” which is very annoying. Recommendations from service professionals of adding octane booster or switching to premium gas have provided no resolution. No system warning lights appear to indicate any operating malfunctions. I could use your expertise and knowledge to help resolve this mystery.
— C.B., Glenview, Ill.
A: What you refer to as plug knock is more accurately called spark knock or ping. It can be due to higher compression than the fuel is designed for. Choosing a higher-octane gasoline often helps. Since you have tried that, we must consider other causes. Carbon buildup on the pistons or cylinder heads is often the cause. Ignition timing that is excessively advanced used to be an issue, but it is now controlled by the engine control module and can’t be adjusted. Piston rod knock may cause the noise, but usually not during a given gear change. However, you can disable the spark plugs one by one and if the noise goes away, it is rod knock.
tQ: I’ve got a 2004 Ford Expedition, and recently when I turned the windshield wipers on they flickered then just stopped. I replaced the switch on the column, but still, nothing. Here’s where it gets weird: If I push the washer fluid button in while simultaneously pushing the rear windshield wiper button for a second at a time, the wipers will inch forward with each push of the rear wiper. What’s wrong?
— M.D., Spencer, Mass.
A: Did somebody put the rear wipers on the front? (Sorry, I couldn’t resist.) It sounds like an electrical problem and could be a bad ground somewhere. Activating the rear wipers may allow the electrical current to find a weak ground through the rear circuit. This will be a fun challenge for a professional tech.
Q: I have a 2015 Dodge Challenger RT with a 5.7-liter Hemi and a six-speed manual transmission. It has not been started in 11 months. I want to know if there is any way to crank the engine to get the oil circulating to the bearings without it starting. Back in the old days you could just pull the coil wire and crank but not sure about now.
— L.M., Mundelein, Ill.
A: Chances are, your engine is fine. When it was shut down, all of the passages and galleys had oil in them. You could simply start the engine. Avoid revving it, though. The perfect alternative is to obtain an engine prelube tank and follow the manufacturer’s instructions. One word of warning: You will be introducing oil into the engine, so make sure the same amount has been previously drained. Better yet, drain and replace half of the oil and let the preluber fill the rest.
Send questions along with name and town to Motormouth, Rides, Chicago Tribune, 160 N. Stetson Ave., Third Floor, Chicago, IL 60601 or motormouth .tribune@gmail.com.