Hi, I've got a Liberty (Legacy) and every now and then, it'll start to 'put'. It idles at about 500 and sometimes will stop if the revs aren't kept up. When you give it throttle, it'll struggle to increase the revs and will make a putting/misfiring noise coming from the exhaust (sounds like at the rear, could be wrong).

It happens mostly in the morning as soon as the car hits running temperature and it gets put under a bit of strain (like up a good hill), but sometimes will happen when put under strain even after it's been running for some time.

It fixes itself if the revs are kept at about 4000 for about a minute, then runs fine.

I've been told it might be the fuel injectors getting clogged, but I've put injector cleaners in the fuel for a little while with no difference. I've also heard it might be the flange gasket (don't know much about those).

Can anybody help? Thanks.