Why is my forester engine loud and shaking when driving fast?

After driving for at least 25 mins at about 80 mph my car enging starts to get loud and shake hard. When I slow down it will continue for a few minutes then eventually stop and then I can resume my speed for a while without a problem. It’s random, sometimes it’s fine.

There are a plethora of possibilities. The most likely is an ignition system that’s become sensitive to heat. Perhaps the coil(s) is(are) failing (you don’t mention the year, so I can’t look up whether it has a single coil or distributorless ignition).

Are there other symptoms, such as the temperature going into the hot range and/or contamination in the coolant…I’m thinking possible headgasket, the breech opening up more when the engine gets hot, but only because I know someone with a Forester that has a blown headgasket.

What’s the maintenance been like? What year is it? How many miles does it have?

Something about this post tells me the answer should be obvious, but I just cannot put my finger on it…

It is a 2006 with 45,000 miles on it. I have the oil changed regularly but haven’t had the big maintenance check. The dealer looked at the engine and said they didn’t see anything wrong. I did at one time roll my front right tire into a ditch and got stuck. The engine was resting on the ground as the car was off the back left tire. Who knows wether it is related to my problem? So I thought perhaps an engine mount was loose. The dealer said everything looked fine. I don’t know if I trust the dealer. I drive 30 mins on the highway 5 days a week and I can go a couple of weeks with out any loud noise. It will do it for sure on a long car trip after an hour or so.

Be sure that the problem is documented on dealership repair orders. If you can document this as having taken place during the warranty period, you should be covered for repairs needed to rectify the problem after the warrany expires.

In the meantime, you might want to kick this up a notch to the Subaru Zone Representative. Contact information is in your Owner’s Manual. The Zone Rep can authorize repairs that the dealership is reluctant to do or is not familiar with.

Does this have a coil-on-plug ignition? VDC’s right that you should document everything and pursue it through the zone rep, however I’m still thinking you have a heat sensitive coil. Perhaps the shop didn’t pick it up because it runs fine when it isn’t hot. They perhaps didn’t take a heat gun to it.

Ask the shop manager (not the service advisor) if you can heat it up and then stop and let them chack it immediately, whille it’s hot.