2007 V70 2.5T engine seems 'unbalanced' under load

zanzabar · Post by **zanzabar** » 16 Oct 2015, 17:38

Car is new to me, just bought used a few weeks ago.

Did: plugs, tbelt, trans fluid, oil change, upper engine mount, transmission torque mount. Idles fine, though lots of vibration through the steering and dash because of poly mounts. Does not seem to hunt for rpms, gets ok mileage. Doesn't seem to have any play in driveshafts, and I don't notice any difference in the noise when load is placed on one side or the other for example when going around corners. Tires I think are balanced, but don't know for sure.

Problem: I just notice a grumbly unbalanced vibration from the engine and can't think of what it could be. I can hear when an engine is working properly and can tell this one isn't smooth. My fear is that one of the rods has spun a bearing, or possibly a main crank bearing issue. No noticeable glitter or metal shavings in recent oil change though. I just feel like this engine should be running way smoother and can't think of how to make it do so or what to check next.

What else should I look for? Any ideas welcome!

zanzabar · Post by **zanzabar** » 20 Oct 2015, 14:14

Regapped the plugs (Volvo oem from IPD) to 0.030" (were 0.026-0.028 before) and it has smoothed out somewhat.

Any suggestions about plug gap? Should I go even a bit more - say to 0.032 or higher? From what I can find spec is 0.028-0.032. Does anyone find that the higher or lower end of that range works better?

Post by **precopster** » 20 Oct 2015, 14:17

Start with a compression test then start doing things like unplugging injectors one at a time with engine running to see if problem stays with certain injector unplugged. That injector may be faulty or clogged.

Post by **chrism** » 20 Oct 2015, 18:31

You say it only grumbles under load. Can you sit in the driveway, hold the brake, in gear, and give it the gas (load on engine) and get the same grumble? Or do you have to be rolling down the road?

Post by **JRL** » 20 Oct 2015, 20:33

Did you check your front lower mount (right side of car)? If it has more than 100K miles check/replace it
When they collapse (not if) all the way, the engine drops and it is riding on the subframe and make a rumble at best.
Poly bushings also do not help one bit, that's why they come with rubber mounts. It's a 5 cyl.... inherently an unbalanced engine.

jpitt-32 · Post by **jpitt-32** » 20 Oct 2015, 21:15

I'll second what JRL said... I had a bad vibration that I would have swore was the tires or a bent rim. Turned out that I found a mount was way gone. When I was climbing a hill under load, engine would rise up enough to trow the cv axle / joint out of balance, it felt almost like the engine was out of balance.

zanzabar · Post by **zanzabar** » 21 Oct 2015, 22:06

I noticed that lower engine mount on the passenger side was looking pretty old, but I'm not familiar enough with what they should look like to know if it was shot or not. This is where I'm going to go next, thanks JRL.

zanzabar · Post by **zanzabar** » 21 Oct 2015, 22:10

JRL wrote: It's a 5 cyl.... inherently an unbalanced engine.

Why?

zanzabar · Post by **zanzabar** » 21 Oct 2015, 22:11

chrism wrote:You say it only grumbles under load. Can you sit in the driveway, hold the brake, in gear, and give it the gas (load on engine) and get the same grumble? Or do you have to be rolling down the road?

Nope, grumble mostly only while rolling down the road.

Idle vibration was awful today with A/C on.

zanzabar · Post by **zanzabar** » 21 Oct 2015, 22:12

precopster wrote:Start with a compression test then start doing things like unplugging injectors one at a time with engine running to see if problem stays with certain injector unplugged. That injector may be faulty or clogged.

Excellent ideas, I have been planning to check compression at some point...just need to carve out some time.