2013 Peugeot 2008 1.2 VTi - White smoke at high revs

[garypg]

Trying to get to the bottom of a problem and have been getting many conflicting views from mechanics. The local engine rebuilder said they've never had to do piston rings on a 1.2 3 cylinder and the problem will be something else.

Anyway, vehicle failed its MOT on emissions due to 'excessive smoke'. There is no smoke or startup or when driving normally. It only occurs when revving at 3,500rpm (ish) and above. What I get is a very light white smoke which smells somewhere between the smell of fireworks and burnt oil.

Engine runs as smoothly as a 3 cylinder does.


Things I've checked:

1. Used a head gasket tester on the expansion bottle

2. Checked the PCV. Dirty with oil but no splits or cracks in the diaphragm. Intake is pretty clean.

3. Spark plugs are slightly sooted. Spark plug on cylinder 3 has carbon build up

4. There is no ingress between the rocker cover and Spark plug o-rings

5. Taken both the intake off and the rocker cover and there is nothing untoward in the oil pump and drain ports or on the cams. The valve stems are clean.

6. Serviced the oil and no white gunk in the old


Things I have done:
1. Changed the oil filler cap, as the old one was leaking
2. Changed the Spark plugs
3. Given it a good run at high revs to burn off any excess

Please help, as I am close to just sending it off to auction.

[CitroJim]

No.3 spark plug being slightly fouled and the smell of the smoke suggests to me that oil is getting into that cylinder somehow...

Spark plugs can only be 'read' properly by cutting the engine at the end of a test run and before the engine has a chance to idle... Plugs from an engine that's been idling for a while may show a little soot and give a false 'reading'.

Perhaps, to try and narrow this fault down, try a brief test run with the PCV system disabled/disconnected with the PCV connection to the inlet manifold blocked.

A quick test of the piston rings is to run the engine at a fast idle when hot with the oil filler cap removed and seeing if there's any signs of excessive blow-by/pressure and smoke issuing from the oil filler...

Do these engines have an EGR valve? I doubt they do but if they do, this may be worth a check too...

[garypg]

Thank you.

I shall test with the PCV port blocked and with the old loose oil filler cap tomorrow.

These engines don't have turbos, EGRs or any other parts which make them more complex. They're quite the old fashioned air intake, throttle body, fuel injector, low pressure fuel pump, cam controlled intake and exhaust valves and exhaust straight to the cat.

The engine shop also mentioned something about the wet belts degrading and blocking the sump intake leading to a damaged crank/cam bearing (can't remember which he said), but I can't see it myself. The wet belt is clearly worn, but most certainly not perishing and is fully intact.

[garypg]

So, I have done a test today:

The engine begins to run rough when the oil filler cap is removed and there's light suction, as you would expect, and not any blow back.

I removed the small pipe between the PCV system and the intake manifold and plugged the hole on the intake. There was a lot of vapour coming out of the breather hole, which is post-PCV. When I plugged it with my finger, the pressure would build in the system.

[CitroJim]

Was there any smoke visible from the exhaust when you did that test?

Was the vapour clear or smoky?

[garypg]

The smoke from the engine exhaust is so little anyway, that I'd really have to rev the engine to get it to produce any. Is it safe to do this with the PCV pipe disconnected, the PCV therefore able to vent freely, but the port on the intake manifold blocked off?

[CitroJim]

Is it safe to do this with the PCV pipe disconnected, the PCV therefore able to vent freely, but the port on the intake manifold blocked off?

Yes, for a short test to prove the point...

[garypg]

To rule out the possibility the engine shop mentioned, I took off the sump pan today and all clean inside, and the oil pickup was clean so, it's definitely not the belt degrading and clogging the pickup.

Once the gasket seal is cured, I'll refill with oil and test at high revs with the PCV disconnected.

[CitroJim]

Looks beautifully clean in there!

[garypg]

Tested at fast idle with and without the PCV connected and results were the same.

However, I noticed something I hadn't before. After high revs, there is a backfire in the exhaust indicating ignition in the exhaust system instead of the combustion chamber.

This leads me onto two new lines of enquiry -
1. Is the timing slightly out? Although it's still in good condition, a worn belt could stretch slightly and cause timing to be off slightly - but there's variable valve timing on these engines, so would it matter?
2. An injector / injectors. Given cylinder 3 spark plug looks sooted, could cylinder 3 injector be the culprit?

Although I've had to reset all the DTCs because of the various ignition errors caused when I've had the various things unplugged, I did notice an error about oxygen sensor 1 outside of range. Would that cause these issues? I will give it a test drive when it goes to the garage on Wednesday and see if it reoccurs.

[CitroJim]

2. An injector / injectors. Given cylinder 3 spark plug looks sooted, could cylinder 3 injector be the culprit?

Could be and also, if each sparkplug/cylinder has its own coil then that coil could be faulty resulting in a high speed misfire. That might well account for the sooting, smoke and backfiring...

If the coil is common to a pair of cylinders (wasted spark) then try another spark plug or a new HT lead on the suspect cylinder...

[garypg]

No further luck on diagnosis I'm afraid.

I've had two separate garages both inspect the car (one a reputable local and another an engine specialist) and say there was a problem with the breather (removing the dipstick triggered a howling noise from the PCV). At great expense and trusting that 2x garages had diagnosed the same thing, I fitted a brand new rocker cover (as the breather system is integrated) and surprise surprise, absolutely no difference. One said to take the vehicle on a long drive but I can't because in the time waiting for garage bookings, the MOT has expired, so can only rev it high on the driveway and around a private industrial estate at the end of the road.

I'm kind of losing the will to live with this one this one and am disappointed I seem to know more than mechanics do (i'm also now on the verge of just sending it off to Copart)?! The engine specialist said the engine runs too well to be anything else and that it could be oil still in the back box, but I removed the spark plugs, cleaned them and cylinder 3 spark plug had oil on it again. Equally, if they said there was a breather problem and exactly the same symptoms and howling with the entire system replaced, this clearly wasn't at fault.

I doubt myself because I've got mechanics telling me different, but surely both garages should have performed a dry and a wet compression test, to confirm piston rings or head gasket oil channels before getting me to spend £300 on a rocker cover. Alas, I have spent another £25 on a compression tester extension in order to test the wells myself (they're too deep to get the flex hose tight enough). I'm expecting a confirmed piston ring failure (I'm assuming that if the cylinders hold more compression with a little oil sprayed, then it is piston rings, and if they don't, compression would be lost though the head gasket still).

[CitroJim]

Sorry to hear this is still going on...

I'm expecting a confirmed piston ring failure (I'm assuming that if the cylinders hold more compression with a little oil sprayed, then it is piston rings, and if they don't, compression would be lost though the head gasket still).

Yes, check compressions dry and then repeat with a little oil (wet) and always check with the throttle wide open.

If the wet test is higher than the dry test then likely a ring/piston issue. If compression is low and does not change then likely a leaky valve, a crack in the head or head gasket although unlikely as a failed head gasket will often give other symptoms...

Keep us posted...

[garypg]

It's not good news I'm afraid.

Compression test results:
Cylinder 1: 115psi
Cylinder 3: 115psi
Cylinder 2: 55psi. Wet test 80psi. Pressure constant during 2 minute test.

I don't have a leak-off tester, so i pressurised the cylinders and then measured any drop during a 2 minute test. Given the pressure held during a 2 minute test on each cylinder, I'm concluding no block issue or head gasket failure. Compression is clearly not sealing properly when the piston is in motion and that therefore points to rings.

...And, that also gives clear evidence oil is not being sucked into the cylinder through the oil ring due to a vacuum from the breather syatem due to blockage. The correct analysis is that compression is forcing itself out of the cylinder, pressuring the crankcase and displacing oil into the combustion chamber on the upstroke.

How could 2 garages not manage to diagnose this?!?!?!

[CitroJim]

Yes, that certainly looks like a piston or ring failure... Not good news... Hopefully you can remove head and sump reasonably easily and then extract the piston for a look.

I fear many mechanics these days are well trained on electronic diagnosis as electrical/electronic issues account for the vast majority of their work and are not as familiar as mechanics of days gone by were with the issue you have and how to diagnose it...

You may now need to toss up the cost of fixing this engine compared to getting a good one out of a scrapper. You may find cylinder damage as well as piston and ring damage. If the cylinder is say, badly scored a replacement engine from a breaker may be the best option...