bad vibes

XRLNT-8 · 08-10-2008, 09:43 PM

Hi all,

I have a vibration problem with the XR8 which must be getting worse as I am noticing it more now but can't put my finger on when it began.

When slowly lifting revs in neutral, it is smooth until 1500rpm then it shudders until over 1700rpm.

When driving, the car shudders while maintaining 1500-1700rpm. It is there even when decelerating, you can feel the shake when the revs drop through the 1500 mark.

If you hold the revs right on the point where you can feel the vibe, you can't see the engine shake, but the exhaust pipes are going crazy (not a factory exhaust anymore BTW).

If it was the harmonic balancer, wouldn't the whole engine shake? I am considering putting a balance pipe into the exhaust as a possible remedy but I would appreciate any input from anyone else.

Regards,

Simon

james22 · 09-10-2008, 11:43 AM

I'd be looking at your harmonic balancer for sure. And no your entire engine wont shake. Also might be worth looking at your engine mounts.... Don't happen to have a little star in your bonnet do you?

Balance pipe has go nothing to do with any of this BTW...

Any more info you could pass along?

XRLNT-8 · 09-10-2008, 09:27 PM

Thanks for the input James,
I will have a look at the balancer this W/E, need to sort this prob ASAP as it's pretty annoying!

Cheers,

Simon

JMO · 09-10-2008, 10:15 PM

I don't have any vibration in the engine while moving only when in 'D' and 'R' and idling. Could the crank (harmonic balancer), aircon, power steering or water pump pulley (idler was recently replaced) be the cause of a rough rough idle? There is a definite sort of 'grinding' noise coming from one of the pulleys (possibly dry bearings) while the engine is running. I've exhausted most causes. Maybe this is it?

james22 · 10-10-2008, 07:44 AM

^^^ Have you tried to pinpoint the source of the griding noise? Try using a long screwdriver as a stethoscope, to locate where its coming from. (be careful lol, keep hair etc away from the belt)
And yes, if for example one of the bearings is absolutely f@**ked, it could cause a rough idle. I had a pulley seize on one of my old cars, and it clean stalled the engine with no effort at all.

JMO · 10-10-2008, 12:22 PM

Thanks for the info. From looking at the pulleys,my money is on the Power steering or crank, purely because the centres are rusty in appearance. The sound seems to be coming from the middle of the pulley setup so it could be the crank. I'll give the stethoscope thing a try. I'm assuming you only put it near the pulley and don't actually touch it?

james22 · 10-10-2008, 12:53 PM

Sit the tip of a (preferably long) screwdriver, at the rear of each pulley. (Ie; on the housing the pulleys mount too, NOT the back of the pulley lol)
It has to make contact so that you can hear through the screwdriver, but you have to be careful and stick your ear to the handle of the screwdriver. You will clearly be able to tell which pulley is making a noise. When you locate the culprit, replace the pulley/bearings and away you go.

Afterthought; Belt tensioners make a bit of noise, so don't be put off by that. and the idler pulley, from previous experiance quite commonly fails. (EA and AU falcon that one lol)