Volvo S60 2002 Engine Shaking

Hi all,

Wondering if we can get some help with this. My wife has a 2002 Volvo S60 that we share with ~165,000 miles on it now. In the last 4-5 years or so, it developed this problem of feeling like the whole engine is shaking when we start it up sometimes. It can go days or even a week where we don’t have this problem and then all of a sudden it happens one morning or afternoon, or whenever without any rhyme or reason. While it’s shaking, the lights on the dash go in and out with the shaking (going between dim and bright). What also happens right before the shaking sometimes is that the engine will rev itself, like its got a mind of its own, sometimes up to 2000 RPMs, like I am pressing on the gas pedal and holding it, but I’m not! It will stay revved up for a good 10 secs or so then come down on its own and proceed to shake. We usually turn the car off, then on again and it goes away. If it doesn’t go away, then we repeat (off/on).

We’ve taken it to the dealer multiple times, including in different cities since we happened to move in the last few years to another city and still, no one can solve the issue. She swears it all started happening after we went a week without the gas tank lid after it got left off by accident after we pumped gas one time. I noticed it was missing definitely within < 7 days and got a replacement right away from the auto store. Not sure if that has anything to do with it?

The car otherwise still runs fine but we just never know when the shaking thing is gonna happen next. It can even happen on the highway when we are driving. You can be trucking along at 70 MPH or so and then ease up on the gas and we’ll feel it in the gas pedal and the car…it will jolt and shake a little until we rev the engine above whatever speed we had decelerated to when the shaking started.

When the shaking has happened, I have gotten out of the car to examine under the hood and cannot see anything in particular, the whole thing is just moving like normal and shaking a bit and then eventually if you leave it long enough, it stops on its own.

Can’t be healthy for the far so any help or knowledge would be great! I tried to video tape it on my phone but it couldn’t capture the essence of it well at all.

Thanks for your time in advance!

Is the check engine light on? Is all the routine engine maintenance suggested in the owner’s manual up to date? Let’s assume for sake of discussion the check engine light is not on, and all the maintenance is up to date …

Since this problem comes and goes, something w/the engine is likely amiss. (If it happened all the time, it might just be the mounts are worn.) Most likely there is some problem w/the fuel/air ratio. So it’s either a too much/too little fuel or a similar air problem, or both. I’d start with the vacuum system. A leak in that will allow unmetered air into the engine, and can cause this symptom. And this can sometimes be intermittant, depending on temperature and the like. Ask your shop to test all the vacuuum lines and devices for breaks or leaks.

If it isn’t that, then searching for places where air can leak in such as a leaky intake manifold gasket, etc, in parallel w/ a fuel pressure at the rail test, O2 sensor test, cleaning the throttle body, and testing/cleaning the MAF (if you have one) is probably next.

It could be something more serious, like a head gasket or compression problem. Shops have tests to say yes or no on both.

A good Volvo shop is what you need. One that has the electronic test equipment that can do real-time engine diagnostics. Ask if the shop can check the fuel trim. If they can’t, that’s probably not the shop to use.

That is an odd one. I assume the car never has been in any water? Ever driven through any deep water during flooding?

I am thinking it has to be sensor related. Have you replaced the oxygen sensors? Driving with the gas cap off for a week could, maybe, cause havoc. Should not, but could. If you have not changed the fuel line filter, that is one inexpensive thing to do, which should be done anyway (not all S60’s have such a filter, but most do). Also, the four engine mounts - have they been replaced? Bad engine mounts could be magnifying the root cause.

I would search online at some of the Volvo forums, see if you don’t have one of those old trusted Volvo garages within 200 miles. Not the dealer, an independent who only works on Volvo’s and are Volvo nuts. I think they are more likely to get to the bottom of it.