VS Idle vibration (STILL)

[nathanVY]

Hi Everyone,

Still having this stupid vibration at idle... only when the car is in drive and stationery... (still does it with the handbrake on), here's what I've done so far trying to fix it..


- Replaced IAC
- Clean TB & Plenum (new gaskets, etc)
- New injectors
- New auto fitted
- New engine mounts
- New gearbox mount

I'm trying to figure out if it's just the exhaust, but it seems theres plenty of other people on here having this problem. The exhaust has been custom made and is very stiff and very close to the body - I have no problem with this because the car is low but I'd rather have the exhaust scrape than vibrate like this.

Of course there's a plethora of things that 'could' cause the issue but I'd like to try and narrow it down a bit more...

Car is a VS V6 S1. Just about to hit 200,000. Serviced regularly since I've had it (170,000).

I'm thinking it could be either or all of these :\

- Harmonic balancer
- Belt tensioner
- Fuel pump / tank (there is a huge dent in the tank
- Vacuum leak.. (it does have one, but I have no idea how to find it)
- Exhaust too stiff / close

So what do you think? Should I keep trying to fix crap on my car or take it to another exhaust shop?

Help much appreciated.

[some_guy]

When you say vibration, Is there a noise being made or can you just feel it?

[Cheap6]

From the description I would have said engine mounts but they've been replaced so...

If it's the exhaust hitting somewhere, there will be witness marks on the exhaust and wherever it ahs been hitting. You would have to put the car up on stands (assuming you don't have a hoist ) and crawl underneath to find that.

A vacuum leak will cause a rough idle (engine miss). To find it depends on where it's leaking from. If it's a manifold gasket, pouring water or spraying something like WD-40 (carefully of course as it's inflammable) around the manifold where the gaskets are while the engine is at idle will temporarily seal the leak and change the idle.

If it's a hose, including the vacuum system inside the car, that will be a process of inspection. Moving the hoses while the car is at idle may alter the idel speed as per the gasket check.

One more possibility is the check valve on the brake booster. That's the grey plastic part the hose pushes onto. The grommet that seals it to the booster also might be a leak source.

[nathanVY]

You can feel it, but there is noise - because of everything shaking. Hope that makes sense, the vibration feels like the whole exhaust moving back and forth badly.

[nathanVY]

From the description I would have said engine mounts but they've been replaced so...

If it's the exhaust hitting somewhere, there will be witness marks on the exhaust and wherever it ahs been hitting. You would have to put the car up on stands (assuming you don't have a hoist ) and crawl underneath to find that.

A vacuum leak will cause a rough idle (engine miss). To find it depends on where it's leaking from. If it's a manifold gasket, pouring water or spraying something like WD-40 (carefully of course as it's inflammable) around the manifold where the gaskets are while the engine is at idle will temporarily seal the leak and change the idle.

If it's a hose, including the vacuum system inside the car, that will be a process of inspection. Moving the hoses while the car is at idle may alter the idel speed as per the gasket check.

One more possibility is the check valve on the brake booster. That's the grey plastic part the hose pushes onto. The grommet that seals it to the booster also might be a leak source.

It doesn't feel like it's hitting, I'd think that would be a lot more noticeable... it just doesn't have any room to move. Thanks for that tip about the brake booster one I haven't checked that one yet!

I had an idea about finding vac leaks the other day... could you not remove the vac point at the throttle body and get an compressed air gun and slowly blow air through it?
That way you could get someone to listen for the leak... But would there be any issues from the air in the system? Or would it just get sucked out... ?

I guess i'll have a shot at the manifold one, there is a mace 25mm manifold spacer on there too there's a possibility that could be leaking.

[some_guy]

The Spacer could most likely cause a leak in the intake system, but that would just cause a rough idle. And i cant see a rough idle with new engine mounts causing you to feel a vibration in the cabin.

[nathanVY]

The Spacer could most likely cause a leak in the intake system, but that would just cause a rough idle. And i cant see a rough idle with new engine mounts causing you to feel a vibration in the cabin.

Yeah if it's not on perfect it would just make it run shit - in general if not just at idle... I didn't install it so I can't vouch for it...

A rough idle is probably all it would take to make my exhaust vibrate though... I'll see if I can get some snaps of the exhaust...

[nathanVY]

Heres some pics of the exhaust (when it was getting flanged at the extractors)

[some_guy]

Well if you can get under the car and still hear the noise (whilst running obviously).

See if you can hold the exhaust still by putting pressure on it with a bit of wood or similar.

If the noise stops, this confirms its your exhaust, take it down to your local shop and see if they can secure it better.

[nathanVY]

Well if you can get under the car and still hear the noise (whilst running obviously).

See if you can hold the exhaust still by putting pressure on it with a bit of wood or similar.

If the noise stops, this confirms its your exhaust, take it down to your local shop and see if they can secure it better.

If think that's the problem though man, it's secured great barely moves at all. Don't exhausts need a bit of room to move?

[some_guy]

That's why they use rubber mounts. my system was pretty much the same as yours, except it joined just after the gear box, and i never had any issues with vibration.

[nathanVY]

There's hardly any mounts on this thing, extractors - maybe 1 in the middle and bolted on at the end, that bit is rubber though I think... but it's still bolted on, not just hanging like they usually are.

[some_guy]

Bolted on at the rear? odd

Mine sits on two rubber hangers. That could possibly be why your hearing a rattle/vibration.

[nathanVY]

Bolted on at the rear? odd

Mine sits on two rubber hangers. That could possibly be why your hearing a rattle/vibration.

Yeah I reckon... I'll take it back there on saturday... if they don't fix it ill try somewhere else...

[MACE]

if could be the emissions vacuum line from the solenoid (back of the manifold), to the throttle body that has come off. Very common on even dead standard cars. If you bought the spacer kit new then it should have come with a section of rubber to extend that pipe. Let us know if it didn't

Cheers,
Steve

[nathanVY]

Hey steve thanks for the post, I did buy the kit new but got the mechanics to install it... do you have a pic by any chance of the bit you're talking about..?

From memory the car's always done this... just wasn't as bad with the stock exhaust.

[HamaTime™]

Nathan, I'll show you tomorrow night when I see you.

[nathanVY]

Likely the next option I'll take with this is replacing the rattling cat.. mostly because I hate the rattling sound but it 'could' be upsetting the idle a tad.

[scvs6]

Hey nathanVS, did you end up finding what the vibration is? Just interested to know because my WH Statesman V6 has a vibration at idle, and if I hold up the revs a tiny bit then theres no vibration. I have checked engine mounts, transmission mount, harmonic balancer, etc. The only thing I keep forgetting to do is clean the throttle body. Been meaning to do it on the weekend but forget all about it.

[nathanVY]

Haven't found it yet mate, thinking I'll do the harmonic balancer next.

Here's a vid of it, reckon it's a bit wobbly?

[nathanVY]

Hey everyone, car was playing up the other day hard starting and rough idle when cold so had a snoop around the engine bay. Replaced the plenum to fuel reg hose (was split on both ends) and the car runs heaps better and the vibration at idle seems to have gone away (THANK GOD).

BUT.

In Park/Neutral the RPM lifts to around 1200 instead of the 'usual' 1000. About 850/900 in Drive. Any ideas? I reset the ECU by taking the engine fuse out for a while but maybe it needs the whole battery off.

Thoughts?

[some_guy]

The revs in my vr used to rise when i was in park/neutral. i thought it was just how the cookie crumbled

[nathanVY]

The revs in my vr used to rise when i was in park/neutral. i thought it was just how the cookie crumbled

Hmm well maybe it is indeed fixed. But I thought that the revs should only rise by maybe 100rpm. Might ring a few places.

[HamaTime™]

Mine revs at about 500 at idle...

[nathanVY]

Mine revs at about 500 at idle...

Lol O_O check plenum to fuel reg vac hose?