Blue/grey smoke after idle

[pacman_1219]

Evening all.

Got this odd issue with my R34 GTT. If I let the car idle for around 15 seconds or more (even when cold) and I jab the throttle a bit, a decently sized plume of blue/grey smoke comes out the exhaust. Doesn't smoke when idling alone, just when giving it some gas after idling.

No smoke on cold start or from what I know, normal driving. Not 100% sure about smoke on decel but I don't think there's any.

Any pointers on what I should start doing to troubleshoot it? Or if anyone has experienced the same I'd love to get some insight.

Cheers.

[GTSBoy]

Is it oil smoke or fuel smoke? They smell different.

[MBS206]

Or if it's grey, is it watery?

Does it do it after you've been for like an hour long drive it will still do it, or just near the start of the trip?

As GTS said, does it seem like oil (blue), water (white/grey) or fuel (black)?

Sometimes the colour can be hard to see clearly too for what it is, as GTS says, what's it smell like?

[pacman_1219]

Not gonna lie my sense of smell isn't the best. But it does look more grey to me. It doesn't smell like oil, friend says it smells like fuel.

[GTSBoy]

Well, in that case it is either completely normal accel enrichment, or it is completely abnormal accel enrichment, caused by a problem that we will be unlikely to be able to guess at this distance, but which will turn out to be f**king weird.

[pacman_1219]

Cheers man, I'm almost a little bit relieved in a way. Let the trouble shooting begin!

[Murray_Calavera]

8 hours ago, pacman_1219 said:

Let the trouble shooting begin!

What ECU are you using?

[Duncan]

Aside from the fact it is likely fuel related if it is black, the symptoms otherwise sound like worn valve stem seals. Oil gets past the worn seals when the engine is off and burns when the engine starts. If it happens on deceleration while driving (puffs of white smoke) that is another valve stem seal symptom because oil gets sucked form the head into the combustion chamber under vacuum with the throttle closed.

They can be replaced in the car if you have some way to keep the valves closed while working (eg compressed air into cylinders) but is much easier with head off.

[pacman_1219]

On 3/30/2025 at 10:18 PM, Murray_Calavera said:

What ECU are you using?

Good question, I don't really know tbh...I'm pretty stock thought, where could I check this?

[Duncan]

In that case it is probably stock. It lives in the navigator side footwell behind the plastic trim just in front of the a pillar.

[pacman_1219]

On 3/31/2025 at 8:02 AM, Duncan said:

Aside from the fact it is likely fuel related if it is black, the symptoms otherwise sound like worn valve stem seals. Oil gets past the worn seals when the engine is off and burns when the engine starts. If it happens on deceleration while driving (puffs of white smoke) that is another valve stem seal symptom because oil gets sucked form the head into the combustion chamber under vacuum with the throttle closed.

They can be replaced in the car if you have some way to keep the valves closed while working (eg compressed air into cylinders) but is much easier with head off.

Cheers man, I thought the same.

 

Bit of an update on it all. It was definitely blue smoke, not grey after all. It didn't really smell oily but it was blue after all. Also puffing just the smallest amount on idle with no throttle.

 

I ended up pulling the intake and exhaust off and there was around 3mm of axial play on the turbo shaft. So I figured we'll that's buggered and sent it off to get hi-flowed at hypergear. Haven't got it back yet.

 

I haven't compression tested it yet. Had a look in the cylinder and cylinder 1 spark plug, looked a bit sooty but not oily. Then I've just started doing my timing belt because it's age is unknown.

[pacman_1219]

At this point I'm just 'hoping' it's the turbo seals. I did speak to someone who said it's normal for these turbos to have a bit of axial play? Not gonna lie I've never checked a turbo for axial play before but you could hear it tapping a bit as I moved it back and forth. Surely that's too much?

My theory is (could be completely wrong), bad axial play, worn bearings, bad seals, oil into dump/compressor side, burns in exhaust = blue smoke.

On a timing belt related note, my crank pulley was missing that front plate that sits in front of the timing belt. It's that metal round plate. It did have the rear one, and the woodruff keys are in the crank which was nice. Can anyone confirm if the NEO det engine has a front plate, im sure it would to protect the front of the timing belt or something.

Water pumps...the pump I got was an NPW (yes grill me if I should've got a genuine one lol). It has a smooth mating surface, kit came with a pretty pathetic looking paper gasket. Do I need to use any RTV or just trust the gasket will work because its a smooth mating surface?

Cheers legends have a good Easter break!

[GTSBoy]

36 minutes ago, pacman_1219 said:

I ended up pulling the intake and exhaust off and there was around 3mm of axial play on the turbo shaft. So I figured we'll that's buggered and sent it off to get hi-flowed at hypergear. Haven't got it back yet.

Just be warned that that turbo will not be a direct re-fit to the car. The exhaust housing is, of course, in the same place. It has to be - it's bolted to the exhaust manifold. So the dump will fit up.

But the centre housing is not as long, so the comp housing will move backwards. This will affect both the turbo inlet and the outlet. There is fab work that needs to be done.

28 minutes ago, pacman_1219 said:

Can anyone confirm if the NEO det engine has a front plate, im sure it would to protect the front of the timing belt or something.

Yes. it has one, it should have one.

28 minutes ago, pacman_1219 said:

Do I need to use any RTV or just trust the gasket will work because its a smooth mating surface?

Paper gasket.

[pacman_1219]

6 hours ago, GTSBoy said:

Just be warned that that turbo will not be a direct re-fit to the car. The exhaust housing is, of course, in the same place. It has to be - it's bolted to the exhaust manifold. So the dump will fit up.

But the centre housing is not as long, so the comp housing will move backwards. This will affect both the turbo inlet and the outlet. There is fab work that needs to be done.

Yes. it has one, it should have one.

Paper gasket.

I see...

Any idea how much fab work is required? I note the Hygear megathread but its like 900 pages

[GTSBoy]

You will need to extend the turbo inlet pipe somehow, which could/might be done with silicone/rubber pipe, but might need steelwork, depending on your intake. And you will need to change the pipework on the outlet in teh same way, but this is more likely to need steelwork.

[pacman_1219]

Update

Got turbo back from hypergear, installed everything etc. Bled coolant, wasn't smoking so I thought beauty she's sorted now.

Went on a drive, car up to temp, let it idle for about 15 seconds, gave it some gas...nice puff of smoke again. Fml

No doubt my turbo was pretty worn anyway but nonetheless frustrating that the problem persists.

[MBS206]

27 minutes ago, pacman_1219 said:

Update

Got turbo back from hypergear, installed everything etc. Bled coolant, wasn't smoking so I thought beauty she's sorted now.

Went on a drive, car up to temp, let it idle for about 15 seconds, gave it some gas...nice puff of smoke again. Fml

No doubt my turbo was pretty worn anyway but nonetheless frustrating that the problem persists.

Did you clean everything out?

Take all intercooler piping off, empty the intercooler of oil, clean the exhaust out, etc?

Intercoolers make great catch cans... Which makes them less useful for intercooling... But very worth cleaning out, along with all adjoining piping.

[pacman_1219]

1 hour ago, MBS206 said:

Did you clean everything out?

Take all intercooler piping off, empty the intercooler of oil, clean the exhaust out, etc?

Intercoolers make great catch cans... Which makes them less useful for intercooling... But very worth cleaning out, along with all adjoining piping.

Nah I did not will have to another time. I only installed a blitz return flow FMIC probably 1000kms ago. When I took the old piping off there was basically no oil in piping.

At this stage it has to be valve stem seals. When I roll down a big hill in gear and then throttle down the bottom, I get the same puff of smoke.

[hypergear]

Steam valve seals are usually responsible for cold start smoke, it goes away once engine warmed up. Disconnect it let engine breathers and let it breath freely, see if problem goes away after a short drive. Also check to make sure engine oil drain pipe is not blocked or kinked. 

Edited May 27 by hypergear

[pacman_1219]

On 28/05/2025 at 12:26 AM, hypergear said:

Steam valve seals are usually responsible for cold start smoke, it goes away once engine warmed up. Disconnect it let engine breathers and let it breath freely, see if problem goes away after a short drive. Also check to make sure engine oil drain pipe is not blocked or kinked. 

Hi Tao,

Thanks for your reply. 

It's been a while and I managed to get the valve stem seals replaced with the head on the car. 

Unfortunately this didn't solve my issue, the car still smokes a lot after idling (to be honest during idle you can see a bit of blue smoke from the exhaust), same after deceleration.

I will try disconnecting the valve cover breathers, do I leave the PCV valve in?

By engine oil drain pipe, do you mean the turbo oil drain?