Car is irregularly shakey on hot idle

[OllieVRS]

I've got an issue that I'm not sure is an issue.

Once the car is fully warmed up it tends to shake every few seconds on idle, gradually gets a bit worse the more it idles. This is most apparent in stop-start traffic. With any revs above idle it disappears completely.

It's not an extreme shake, but quite noticeable. I don't get the shake on cold or warmish idle.

Any ideas what it could be?

[ald1717]

I've got an issue that I'm not sure is an issue.

Once the car is fully warmed up it tends to shake every few seconds on idle, gradually gets a bit worse the more it idles. This is most apparent in stop-start traffic. With any revs above idle it disappears completely.

It's not an extreme shake, but quite noticeable. I don't get the shake on cold or warmish idle.

Any ideas what it could be?

are you sure its not the puttering that most gti mk5s do, only happens at idle when hot after a minute or 2, it does it on mine and has done since day one, have heard some say that the updated rear pcv hose with the check valve cures this so if someone has fitted one they will hopefully chime in,

[OllieVRS]

are you sure its not the puttering that most gti mk5s do, only happens at idle when hot after a minute or 2, it does it on mine and has done since day one, have heard some say that the updated rear pcv hose with the check valve cures this so if someone has fitted one they will hopefully chime in,

It could be, happens exactly as you describe it after a minute or 2. I initially thought it may be the oil pump seizing, but it wouldn't make sense that it happens when the oil is hot, i.e. least viscous.

But I'm not sure what you mean by the rear pcv hose with the check valve. If it's something that easy and cheap to replace, I'd be interested in doing it.

Others on the forum say it could be carbon build-up on the intake valves, but I don't know how carbon build-up would cause such an irregular symptom that only appears after a minute or two.

[JoshB]

Is it a new issue? Just wondering if it could be a symptom of the intake. The MAF sensor is known to be very particular and the bracket on most intakes for it is a bit different f an afterthought.

[OllieVRS]

Is it a new issue? Just wondering if it could be a symptom of the intake. The MAF sensor is known to be very particular and the bracket on most intakes for it is a bit different f an afterthought.

Nope, it's been there since I got the car. Probably should've mentioned that in my last reply.

[pudding]

It's misfiring, basically. 

Unless the fuel mixture and injector spray pattern are absolutely perfect, they run pretty rough.  * The possible causes for that are numerous.

Persistent hard misfires from failed injectors or coils are counted, and then stored as fault codes if a threshold is met or exceeded.  No codes = mechanical issues.  See *

[Jons1001]

Sorry can't help you diagnose the issue but just reminded me something that happened the day after I bought my mk5. I was idling in a supermarket carpark and the whole car just started violently shaking  i  though here we go I've obviously bought something with major issues. However after turning the engine off and on again I've never experienced anything since and this was about 18 months ago.

[ald1717]

my car has a new fuel system both pumps,injectors, fuel sensors, coils, plugs, pcv, cam chain and tensioner, maf sensor,carbon cleaned, and its always done this, the only issue i have left to sort is the slight chain rattle when warm which has been put down to weeping cam plate seals, but this wouldnt cause the misfires at idle when hot.  and pretty much all the other mkvs owners i have spoken to say there car does the same,

[JoshB]

My car does say use 97RON fuel on the fuel cap. I know it’s a contentious issue but I put “normal” petrol in mine a few weeks back when I was stuck up the moors in snow and it ran very rough every morning. Would bunny hop for the first 50M, and occasionally when putting my foot down would just bog down.
I don’t really let mine sit at idle so can’t say I’ve experienced the issue, but since filling back up with V-Power all my issues have gone away.

[pudding]

My fuel door says 98 RON, and also in smaller writing underneath - 95 RON (see owners manual).  To be honest, I've noticed minimal difference between Shell V Power and Shell E10......but if I use supermarket 95, then yeah, it's not great.  The difference between E10 and V power costs me approx £50 a month at the moment, so I won't be using that again for the foreseeable.

[OllieVRS]

My fuel door says 98 RON, and also in smaller writing underneath - 95 RON (see owners manual).  To be honest, I've noticed minimal difference between Shell V Power and Shell E10......but if I use supermarket 95, then yeah, it's not great.  The difference between E10 and V power costs me approx £50 a month at the moment, so I won't be using that again for the foreseeable.

The highest I've ever put in my Octy is 97 RON on the rare occasion I was in Northern Ireland. Here in the south I have to add 75ml Miller's Power Plus octane booster to compensate for Ireland's 95 RON (the only RON available here), so as long as the octane booster is doing its job, the shake isn't caused by this.

As far as I can tell there's no change in the sound of the engine when the shake happens, but that's not to say that it's not a misfire.

It's just a bit disturbing when I sit at the traffic lights and I feel like my engine is trying to tell me about its own impending doom.

[pudding]

It's not a misfire, rather incomplete/poor combustion.

It's especially bad during warm up, as a different injection strategy is used, due to direct injection being sh1t at cold starts.  The ECU fires the injectors close to TDC after the swirl flaps have done their job speeding up the gas flow to improve low rpm cylinder filling. Due to this carefully tuned airflow + injection timing balance, any interruptions to the air flow will cause a poor burn, hence the shaking.  Said interruptions are caused defective/missing swirl flaps, excessive carbon build up, worn injectors or just age related wear and tear.

Once warmed up, the ECU switches to normal injection mode and things should smooth out again.

If you had a hard misfire from coil/injection failure, or a damaged piston or valve, you would know about it, so there is no impending doom to be concerned about.

[TornadoRed]

Mine does the same I've been wondering what it is for a while.
Does not happen all the time but yeah in traffic I find it so noticeable. The other day it was quite bad and noticed from the exhaust it was sort of puttering or letting pff pff noise is the best I can describe it. Is this something that needs to be fixed before it breaks down or should it be okay.

[ald1717]

from my own car like the op said like the 2 ops above the intermittent shake only happens when fully warm not when cold, my car does have the odd stutter when cold starting, but the shake is definately only a hot idle intermittent issue, when it first happened i assumed it was heat soak causing it as it only happened when engine properly hot and then standing for a minute or 2

[pudding]

Mine does the same I've been wondering what it is for a while.
Does not happen all the time but yeah in traffic I find it so noticeable. The other day it was quite bad and noticed from the exhaust it was sort of puttering or letting pff pff noise is the best I can describe it. Is this something that needs to be fixed before it breaks down or should it be okay.

You won't fix it unless you replace the cylinder head (or get yours refurbished), so just ignore it.  It's normal, don't worry about it.