Auto Q&A: Ridgeline experiencing mysterious surges

It can be challenging sometimes to determine if a surge or stumble may be caused by the engine or transmission.

The 2017 Honda Ridgeline.
The 2017 Honda Ridgeline. –TNS

Q: My wife has a 2017 Honda Ridgeline with a 3.5 liter engine. I’ve noticed that the truck surges, or seems to be searching at various low speeds, during light throttle. You can not only feel it but it also appears on the tach. So it’s not my imagination. There are no check-engine lights, nor have there ever been. At a recent stop at our Honda dealer, I asked the service department if they had ever heard of this, and the answer was no. Our local mechanic says it’s the transmission.

Your thoughts or suggestions?

— Dennis in Pa.

A: It can be challenging sometimes to determine if a surge or stumble may be caused by the engine or transmission.

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Perhaps you might try this: Find a road condition where your symptom appears such that you can readily duplicate them. Then repeat the drive using the manual shifting mode to hold a gear that results in a slightly higher tachometer reading than before.

Does the symptom go away? If so the transmission may have been downshifting/upshifting, and that’s what you were feeling.

Another check is to leave the transmission selector in auto mode and ever-so-lightly press on the brake pedal with your left foot as you continue to drive normally. This should unlock the torque converter clutch, resulting in a consistent (slightly higher) tachometer reading (assuming no gear shifts occur). If this changes the symptom, it’s likely what you were feeling was the torque converter clutch disengaging/re-engaging when driving normally.

Your torque converter clutch, during light load operation, locks the torque converter to eliminate slippage (slippage is good for power/bad for fuel economy). Most vehicles try to run in the highest gear possible with the converter clutch engaged for good fuel economy. Depending on vehicle speed and load, it’s normal for a transmission to upshift/downshift, and engage/disengage the torque converter clutch at various times. And with fuel economy a priority, there can be a lot of this.

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Modern vehicles are pretty smart. In Honda’s case, they employ “grade logic” to minimize excessive gear hunting, but the PCM (powertrain control module) still can’t see the road ahead and anticipate every rise and fall or curve like a human might, avoiding a shift or clutch change as another will soon be needed.

It’s tough to say if you have a problem or if it’s just an unusual road condition your wife may be encountering. With a six-speed transmission and torque converter clutch, there will be quite a bit of gear/clutch juggling as the PCM attempts to provide optimum performance and fuel economy under a variety of conditions. If there isn’t a check engine light, chances are everything may be operating normally.

Pulsing brake lights: There ought to be a law … wait, there is

By Bob Weber, Chicago Tribune

Q: Last week, I was behind two different cars that looked like they were tapping their brakes, but after following them for a while, I realized that the brake lights had a pattern of four blinks each time. Is this something new built into the cars? Very annoying!

— C.S., Lansing, Ill.

A: Oscillating or pulsing brake lights are not legal, but that doesn’t seem to stop people from installing them. The National Highway Traffic Safety Administration denied a petition for rulemaking from Mercedes-Benz to amend the federal lighting standard to permit the optional use of brake lights that would flash under higher levels of deceleration. Yes, those flashing lights are annoying and I would like owners to get tickets. And, don’t get me started on those super bright LED light arrays being installed on front bumpers.

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Q: Why do some cars like my 2015 Sonata not allow me to have the air recirculate mode on when I have the front defrost clearing the windshield? It pulls in a nauseating level of diesel exhaust fumes and dirties the glass even when I’m not right behind a bus or truck.

— J.G., Elmhurst, Ill.

A: To clear the windshield of fog (moisture), dry fresh air is required. Moist air inside the cabin is the source of the fog. As we breathe, we exhale moisture. Things get even worse as the weather gets colder and wetter and we drag snow into the car. If you have ever seen someone driving down the road will all the windows fogged up, it is because they have the recirculate mode selected.

Q: While I certainly agree that some shops (especially at car dealers) have “recommended” services that are beyond crazy, I’m wondering if you can expand on the advice you provided to B.S. in Ingleside, Illinois. Your comment about measuring copper got me searching the internet and interestingly enough, many now say what you say, that measuring copper is more important and water is not a problem these days. However, plenty say water is still the issue and that means your fluid should be changed based on time vs. mileage.

— D.M., Glen Ellyn, Ill.

A: Brake fluid is hygroscopic. Water boils at a lower temperature than brake fluid. During heavy braking, the water may boil and become a vapor. It is like having air in the system and brake performance drops way off. Copper is a predictor of brake system problems indicating a breakdown of the corrosion inhibitors. When copper corrodes, iron and steel are sure to follow. Periodically changing the fluid gets rid of both water and copper compounds.

Q: As a muscle car and convertible enthusiast, I am looking to buy either a 1968 Buick Electra 225 with 430 cubic inch motor or a 1975 Buick LeSabre with 455 cubic inch motor. As a result of today’s unleaded gasoline with 10 percent ethanol, please help me to understand what troubles or adjustments I need to prepare for either of these two engines.

— R.K., Chicago

A: Cars built before the 1970s lacked hardened valve seats in the engine. When unleaded gas was introduced, there was fear that valve recession would occur. Lead from the gas used to create a kind of cushion on the seats. In the years since then, valve seat recession has not been a big problem. Unless you race or tow heavy loads, you should be fine. As for ethanol laced fuel, there isn’t a problem.

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