Vibrations and resonance. Engine mounts?
 

My Volvo S40 T4 from 1997 vibrates quite a lot. It does that in all the rev range, but it varies across. When idling it vibrates constantly inside the car: through the wheel, pedals... everything. When I accelerate certain parts of the cockpit start getting into resonance depending the rpms, for example, between 1500 and 2000 some plastic behind the wheel does great noise.

Could be engine mounts? I looked at the engine bay at I didn't see crazy movement like in this video, so not sure about it.

Most likely motor / tranny mounts. Some will allow more engine rotation than others, while other mounts couple more noise and vibration into the cockpit. If they're the original (antique) mounts, they're due anyway.

Yep. Engine mount it is.

https://cimg3.ibsrv.net/gimg/volvofo...b325485204.jpg

Thanks habbyguy.

I'd replace all of 'em while I'm at it (if one is totally shot, the others are at best right behind it). Let us know how wonderful the car feels after you do replace those mount(s)...

And consider yourself lucky - the mounts on an S40 / V50 are pretty simple to swap. My "new" ride (2011 Mercedes GLK 350 4Matic) took about 10 hours and involved dropping the exhaust system and removing the axles, special tools, etc. Ugly job but WOW it's a different car with new mounts!

Bad news. Changed the mounts and it did run much better... for a while. Next day it was as bad as before.

I might have damaged them as I had to force the whole system to get them in place: old mounts were deformed and the hole of the front mount (were the screw rests) was off centered.

There are a lot of possibilities at this point. Yeah, could be a new "bad", or "damaged by install" motor mount. I'm wondering if it could just be something like a misfire or other internal engine imbalance causing the cockpit vibration (enough that the motor mounts can't contain it).

For the vibrations to be transmitting through and to the cockpit means that there's got to be a fairly large "issue" somewhere. If the engine is shaking enough that it's still hammering the cockpit with new mounts, I'd suggest that you should be able to feel this (should be obvious) vibration with a hand on the valve cover. The Volvo I5 is a pretty smooth engine - not sure you can balance a quarter on the valve cover at idle, but "pretty close to that". If you can feel an obvious vibration in the engine itself, you have a very different path to resolution of the problem.

The fact it vibrates at idle (not moving) does tend to rule out other drivetrain-related issues (CV axles, differential(s), wheel bearings, etc.).

BTW, did you replace the transmission mount when you did the motor mounts? I tried looking up the mount, but it's confusing since (apparently) the S40 wasn't sold in the US until 2000, so I plugged that year into my (rockauto) search.

Thanks for the response habby.

Yeah, the engine vibrates. You can see it when you open the bonnet, not even mentioning when you put the hand on it. The previous owner tells me he changed the hydraulic mount, and I did the front and rear of the engine.

The engine has been using 95 octane instead of the 98 recommended by the previous owner. Maybe that caused misfire... but it has been fine for months. It's also weird that right after I changed the mounts, it worked brilliantly... until the next day, when it started to vibrate again.

Going a few points down in octane shouldn't cause misfires. But if you are getting misfires, you need to chase down the source before going further looking for ways to control the vibration due to the misfires.

Throw a code reader on the car and see what it tells you. If the misfire is specific to one cylinder, swap the plug to a neighboring cylinder, and the coil to another, and see if the problem stays the same or follows the plug or coil. After that, it's the same with the injector(s) and then it's off to a compression test.

Some will allow more engine rotation than others, while other mounts couple more noise and vibration into the cockpit. If they're the original (antique) mounts, they're due anyway.

I have same year 1.6 and it vibrates alot too. No power loss nor hesitations though. I suspect that the engine is just worn out. But i'm gonna try replacing the thermostat and see if it helps.

Also i not long ago changed spark plugs to volvo recomended ones (4 headed ones) . If the car has no vvt and has old kind of spark plug wires, the wires should be checked and pressed in well (tap hard with an end of a screwdriver) and made sure that the wires do not touch eachother.