Technical Oil fouling and no firing on cyl 2 plug on 2001 Seicento MPI

[Jamieboy]

I’m trying to solve a problem with a misfire on cylinder 2 in my 2001 Schumacher MPI Sei. I collected some information today using various tests alongside Fiat ECU Scan to fire injectors/coil banks.

Symptoms:

• Obvious misfire, car is running on 3 cylinders, does not clear with revs.
• Cyl 2 injector actuation sound is substantially quieter/weaker than 1, 2 & 4 - barely audible in fact. This makes me think there is zero fuel being delivered.
• Spark plug on cyl 2 has fresh oil fouling, even after repeated cleans.
• After cleaning, plug has been verified operating/swapped with adjacent cylinder.
• Spark is present on plug when tested out of engine using Fiat ECU Scan to fire coil banks.
• Using a borescope to get a better view down cyl 2, oil is evident in cylinder and around piston crown, along with a fair bit of carbon/garbage. Cylinder 1 shows some liquid present also, but could be fuel from repeated injector tests.
• Slightly sooty plugs 1, 3 & 4. ECU enrichment compensation for non-firing on cyl 2

Cylinder 2 view down the sparkplug hole........................................and.....................cylinder 1 for comparison

Other information -

• The car came like this, it is not a problem which has developed during my ownership.
• No coolant being used, no exhaust gas smell in coolant, no coolant in oil.

Tests to be carried out in order of labour-intensity –

• Compression test may rule out or indeed suggest oil control rings.
• Removal and inspection/cleaning of injector may reveal something.
• Pulling the cam cover, cam & replace valve stem oil seals in the event the oil is originating there.

Question before proceeding -

Is it possible that a dysfunctional injector could cause oil in the cylinder as a result of there being no firing? i.e. could a cylinder which has been idling for an unknown amount of time be pulling oil from somewhere?


As always, any assistance or guidance would be much appreciated!

 

[bugsymike]

Not a five minute job , but personally I would do a leak test as more precise than a compression test in telling where loss is.
All you need is a air compressor, hose and adaptor to fit plug threads.
If it is definitely oil on piston and not petrol, it does point towards pistons/ rings.

 

[Jamieboy]

Not a five minute job , but personally I would do a leak test as more precise than a compression test in telling where loss is.
All you need is a air compressor, hose and adaptor to fit plug threads.
If it is definitely oil on piston and not petrol, it does point towards pistons/ rings.

Thank you for the advice Bugsymike, I hadn't heard of that test. What sort of pressure is sensible for it?

 

[bugsymike]

Thank you for the advice Bugsymike, I hadn't heard of that test. What sort of pressure is sensible for it?

I have mentioned it in the past here, it involves around 90psi although I generally use my compressor set at 150psi.
There is proprietary pieces of equipment to do this and I do have one for diesels.
The difference is they have all the adaptors and a gauge to measure the % loss etc.
What you do basically is set the cylinder your testing at TDC on the firing stroke so valves are shut etc. then lock the engine from turning, as even a few degrees of movement may allow a valve to open. Then via a adaptor in the plug hole (I have made them from an old spark plug welded to a airline fitting in some cases) introduce the high pressure air into cylinder. In your case you suspect the seal between piston and bore, so you would be able to detect air blowing from oil filler cap as pressure would have escaped past the piston into the crankcase/sump area.
If exhaust valve was leaking you would hear it at the tail pipe. Note some care may be needed with all the modern EGR etc. to confirm actual source of air leak. It was easier in the days of simple carbs.
Inlet valve at the inlet manifold area.
Head gasket blowing into cooling system, even a small leak can be seen by leaving the rad cap/expansion bottle cap off and filling with coolant to the brim, after a few seconds it can start to overflow if leaking.
The advantage of this test is it can accurately point you in the direction to investigate, as often with engine stripped down, a small fault may not be apparent.
The disadvantage is as the test has to be repeated with each cylinder it can be time consuming.
I was first introduced to this equipment in the late 1970s working as a foreman for a Lada Dealership we got an award for best workshop, the prize was a selection of Sun Tuning Diagnostic equipment and a petrol cylinder leak tester was amongst the tools.
Anyone trying this test needs to make sure all hoses etc. are air tight and compressor far enough away, so no odd noises spoil test.
In your case where suspecting a piston sealing issue you may want to do a "dry" compression test followed by one introducing a little oil down the cylinder bores, if the "wet " test gives a higher compression reading it indicates a poor piston/bore seal. So all you would need is a petrol compression gauge.
One point anyone doing this test and not locking engine from turning will cause the alternator belts/pulleys etc. to turn so as in most things with vehicles a bit of commonsense is required for safety reasons.

 

[Jamieboy]

I have mentioned it in the past here, it involves around 90psi although I generally use my compressor set at 150psi.
There is proprietary pieces of equipment to do this and I do have one for diesels.
The difference is they have all the adaptors and a gauge to measure the % loss etc.
What you do basically is set the cylinder your testing at TDC on the firing stroke so valves are shut etc. then lock the engine from turning, as even a few degrees of movement may allow a valve to open. Then via a adaptor in the plug hole (I have made them from an old spark plug welded to a airline fitting in some cases) introduce the high pressure air into cylinder. In your case you suspect the seal between piston and bore, so you would be able to detect air blowing from oil filler cap as pressure would have escaped past the piston into the crankcase/sump area.
If exhaust valve was leaking you would hear it at the tail pipe. Note some care may be needed with all the modern EGR etc. to confirm actual source of air leak. It was easier in the days of simple carbs.
Inlet valve at the inlet manifold area.
Head gasket blowing into cooling system, even a small leak can be seen by leaving the rad cap/expansion bottle cap off and filling with coolant to the brim, after a few seconds it can start to overflow if leaking.
The advantage of this test is it can accurately point you in the direction to investigate, as often with engine stripped down, a small fault may not be apparent.
The disadvantage is as the test has to be repeated with each cylinder it can be time consuming.
I was first introduced to this equipment in the late 1970s working as a foreman for a Lada Dealership we got an award for best workshop, the prize was a selection of Sun Tuning Diagnostic equipment and a petrol cylinder leak tester was amongst the tools.
Anyone trying this test needs to make sure all hoses etc. are air tight and compressor far enough away, so no odd noises spoil test.
In your case where suspecting a piston sealing issue you may want to do a "dry" compression test followed by one introducing a little oil down the cylinder bores, if the "wet " test gives a higher compression reading it indicates a poor piston/bore seal. So all you would need is a petrol compression gauge.
One point anyone doing this test and not locking engine from turning will cause the alternator belts/pulleys etc. to turn so as in most things with vehicles a bit of commonsense is required for safety reasons.

Thank you so much for taking the time to write this comprehensive reply, I greatly appreciate it. I will get the required kit together and post my results.

 

[bugsymike]

Thank you so much for taking the time to write this comprehensive reply, I greatly appreciate it. I will get the required kit together and post my results.

If you look up online it may help further.

 

[Jamieboy]

If you look up online it may help further.

No discernable leaks on that test, so I moved on to inspect the injector on cyl 2 on the bench. The two halves separated at what looked like failed welds on its casing and I managed to clean all its internals and rebuild. On the bench, it was acutating fine, but in the car, with ECU scan, it missed out half of the pulses in the test. I cross-corrolated the injector operation with electrical feed from cylinder 1 (same dysfunction) and tried cylinder one's injector on cylinder two (correctly operating).

Long story short, I bought an injector and everything is working as it should - car now runs very well.

 

[Jamieboy]

A short video showing it now running smoothly.

 

[varesecrazy]

Not sure that explains 'oil fouling.. '

But good to hear it's running better

 

[Jamieboy]

Not sure that explains 'oil fouling.. '

But good to hear it's running better

Thank you!

I am wondeirng about the effects of it being run for a long time with no fuel delivery in that cylinder. If the valve stem oil seal is failing and the excess oil has been pooling (which would otherwise be burned if the cylinder were firing), that may account for it. I will monitor plug colour and at some point, I will pull the cylinder head and know for sure.