Engine Vibration at approx 2000 RPM

[ICE_BM]

Hi H6 drivers,

I have an engine vibration at about 2000RPM, it's not really bad but certainly noticeable. Car is MY08 auto SpecB (3.0L standard NA), done 60000km with regular servicing.

I have read through other posts for ideas, I don't think it's coming from the exhaust, seems to be more from the front of car. I say 2000 RPM because it's there in all gears, but more noticeable at cruise speeds on freeway.

I can't imagine it's 'normal', but as new owner of car who can say? Car has good power and bad fuel economy, I think that aspect is normal though

What kind of things are likely, anyone else have this or heard of it?

[Dropz]

is it a rattly sounds or is it a vibration that you feel?

The timing chain tensioners can get noisey sometimes.

The H6s do have good power but yes expect the economy to be around 13l/100km depending on driving style.

[ICE_BM]

I reckon it's vibration not rattling. If it was at a certain road speed then I would say driveshaft for sure, but since it's at a certain RPM regardless of road speed I think it's from the engine.

I was reading the oil checking thread and have now got thoughts that the previous owner may have not been paying good attention to levels. Fingers crossed I'm wrong. Having said that the vibration doesn't get worse at higher RPM, it mostly goes away.

Happy to be corrected on my interpretation and open to all ideas.

Notes:
With the fuel economy the way it is (and needing to run premium) I might as well be running a V8 and have more room for passengers (I'm a tall guy and former Fairmont owner...) On the freeway it will drop to 9-10L/100 but around town 15-17L/100 is common, and I'm trying to drive it calmly to save fuel. The big flatspot lowdown (which is normal for these I believe) means you have to sink your foot into it to get off the line, that can't be good for economy. What would be ideal (in my opinion) for driveability is to have the [S#] power curve running to the [I] gearshift profile, I'm certainly going to look into ECU re-profiling once I get past my other teething problems with this car.

[Dropz]

15-17 is high. I'd be getting it checked. Maybe try clearing the memory might help a bit too.

[zch91]

Definitely send KiDo_tuning a PM if you're looking into smoothing things out and tweaking

[Dropz]

If the vibration is felt in the cluth pedal it could be thrust or spigot bearing. Flywheel out of balance, bad engine knock (noisey though) or misfire/ detonation.

[ICE_BM]

Hi people who have answered, thanks for your thoughts.

It's an auto, so no clutch pedal.
I assume auto uses more fuel than manual, so with this in mind is 15+L/100 still high?

This next question might belong in another thread, but relates to the suggested solution of clearing the memory: does anyone know what the conditions for a 'drive cycle' are? I have been told that after clearing memory and any DTCs that the car must go through some number of drive cycles before some DTCs may be re-evaluated (maybe only one drive cycle). In any case, I'm led to believe it's a combination of time, speed, rpm, distance. Reason I ask is that I have an intermittent code 420 coming up. It seems to occur on my longer freeway drives but not quite repeatable. The drive cycle question comes about because I suspect that my usual drive to work might be not long enough or far enough to register as a 'drive cycle', and so what might appear to be an intermittent fault could actually be a hard fault. Anyone comment on that?

DTC=Diagnostic Trouble Code(s)
420=Catalytic Converter Efficiency Low (but CATs look good, they have been eyeballed and flow well)

[3rspecb]

Do you have aftermarket exhuast ?

If not, then how does one eyeball the stock cats ?


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[ICE_BM]

It's a good question...I am relying on the advice of the mechanic there.

He told me that he undid the flange(s) and inspected the honeycombs. His reason for doing this was that he'd recently had another car that is specified for premium fuel come in with blocked CATs. Although the 420 fault is most likely to be a bad oxygen sensor, he seemed to say it was worth inspecting first, since I have not had the car from new and who knows what fuel the previous owner might have put in. I suppose he may have used a camera on a stick, unlikely, so it seems from looking at the exhaust layout diagram that I might have been taken for a ride with that advice. Lucky there was no stripy paint available there or I might have bought some

Have you got the parts list that goes with the diagram you posted? Anyone tried fitting the O2 sensor spacer to the rear sensor?

Here is a different layout for the exhaust though (year model unknown, but later advice says that the file below is for earlier H6 outback with single tailpipe, so the file here is NOT MY08, but I'll leave it here in case someone would like it...updated the file name to suit):

H6_EXHAUST_Early_Single-Tailpipe.pdf

(87.7 KiB) Downloaded 282 times

[666]

For the vibration check the harmonic balancers.

Rob.

[Tradewind]

ICE

That file you attached was for the old H6 fitted to the first 6cyl Outbacks with single exhaust port

[ICE_BM]

Hi Rob/666,

when you suggest to check harmonic balancer, do you mean 'replace and see if that fixes it', or some other way to check? I have not looked at balancer on this motor, is it conventional 2 piece with rubber compound?

[Dropz]

Yes it's a 2 piece. Check it visually with engine idling. If it appears to wobble it is out of balance and not doing its job. Yes it sounds like the catalytic converter check was taking you for a ride.


15+ l/100km is still high for an auto unless your constantly doing a hills run?

[666]

Hi Rob/666,

when you suggest to check harmonic balancer, do you mean 'replace and see if that fixes it', or some other way to check? I have not looked at balancer on this motor, is it conventional 2 piece with rubber compound?

Sorry for the late reply.

Pretty much what Dropz quoted, check at idle to see if it's wobbling. Even a slight wobble at the right rev speed will induce a vibration. The harmonic balancer is the main pulley attached to the crankshaft, in case you didn't know.

These sometimes fail due to the rubber perishing or a severe shock to the engine similar to a front end accident causing the pulley to move.

Other than that you could put the car onto a chassis dyno and visually see if anything is out of place.

Rob.

[m1keb1ggs]

I have a Outback 3.0R with the 5sp auto and also get a vibration at 2000rpm, but only when under load in 1st or 2nd, so usually pulling away from a stop or out of a slow corner. It doesnt do it any other time.

Could be a similar issue? I was thinking torque converter.