Volvo Mysteriously Revs up in Left Turns

Dear Car Talk

Dear Car Talk | Mar 01, 2018

Dear Car Talk:

I just bought my wife a new Honda and inherited her old 2005 Volvo S80 T6. My "new" ride has 182,000 miles on it, a killer stereo and an odd problem I've never seen before: When making a left turn while moving, the engine will rev, as if in neutral, when I step on the accelerator. Once I take my foot off the gas, the car finds a gear and I can accelerate normally. This doesn't occur when making a right turn, and it doesn't happen if I come to a stop before turning left. Have you seen this issue before, and is it anything to be concerned about? Thanks! -- K.C.

It's not a problem, as long as you're willing to make three right turns every time you want to go left, K.C.

Actually, this sounds like a classic case of a bad motor mount.

There are four mounts that attach the engine and transmission to the frame of the car. These mounts serve two purposes: They hold the engine and transmission in place, and they provide cushioning to isolate the engine's vibrations from the rest of the car -- so your teeth don't chatter while you drive.

If one of your motor mounts is broken, the engine will be able to move out of place, and depending on which mount is bad, it could be at its worst when you're making a left turn. My guess is it's the mount closest to the firewall.

And when the engine moves, it's probably pulling on the transmission's shifter cable, and momentarily putting the transmission into neutral -- just as if you had shifted into neutral yourself.

When you lift your foot off the gas and the engine returns to its proper position, the problem corrects itself. So ask your favorite mechanic to check for a bad motor mount. At our shop, we open the hood, put the car in gear, plant a foot firmly on the brake pedal, and then step on the gas -- bringing the engine speed up to roughly where it is when you experience the problem.

By the way, don't do this with the car facing anything, or anybody, you care about. If a motor mount is bad, you'll actually see the engine lift up out of its cradle. And I'm guessing yours will lift up a lot. So stand back.

That test will tell your mechanic if a motor mount is bad, and, if so, which one. And if you get the mount fixed, this thing ought to run like a dream again, K.C. At least for another week. Good luck.

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