Hello all, looking to see if anyone has experienced what my Octavia is currently doing. Its a 59 plate mk 2.5 with the 1.4 tsi CAXA engine. Its misfiring like hell and after doing a compression test going left to right, C1 - 152 psi, C2 145psi, C3-20psi, C4- 90psi. Turbo has signs of oil going into the throttle body. Blue smoke is coming out the exhaust in bits and kinda at a loss on where to look. Only codes i get from the ECU is cylinder 3 and 4 misfire and random misfires occuring. Does anyone else have an idea on what to look at from previous issues.

It has had all new ignition coils and sparks along with testing known good sparks and coils with no change in the issue. I have stuck a camera into the cylinder also which shows nothing out the ordinary (typical 100k+ carbony engine).

C3 and C4 are way down especially C3 at 20psi . It could be a failed HG on C3 and maybe C4 but it could be a broken valve spring or burnt out valve etc. The misfire will be down to poor compression on 4 and no compression on 3. Unless theres an obvious broken valve spring I reckon head may have to come off to check.

Alasdair

1 minute ago, Alasdair1 said:

C3 and C4 are way down especially C3 at 20psi . It could be a failed HG on C3 and maybe C4 but it could be a broken valve spring or burnt out valve etc. The misfire will be down to poor compression on 4 and no compression on 3. Unless theres an obvious broken valve spring I reckon head may have to come off to check.

Alasdair

I did wonder if that would be the case. During compression testing i did also remove all caps like expansion tank, oil cap and dip stick to hunt for a possible leak which when done wouldn't drop pressure.

Edited 12 April12 Apr by PhilDaJe11yFish

The oil in throttle body and blue smoke as you say in bits so I assume its not all the time. My old volvo 940 used to do the same re smoke. If it was idling for a while when I took off it produced blue smoke due to seals failing in turbo which cleared once driving. The intercooler on mine was full of oil.

It may be that the smoke and misfire are not related and are coincidence but the low pressure test reading does point to HG or valve spring/seating problem. I would redo the pressure test to make absolutely sure. I normally remove all plugs so engine spins at max speed. If its the same then further inspection of head/valves I think is required. It may be that the valves on the cylinders that are low and lower are carboned up so not making a good seal especially c3 or as said weak broken springs. Check the coolant level plus check for any signs of oil/bubbles in coolant.

Alasdair

3 minutes ago, Alasdair1 said:

The oil in throttle body and blue smoke as you say in bits so I assume its not all the time. My old volvo 940 used to do the same re smoke. If it was idling for a while when I took off it produced blue smoke due to seals failing in turbo which cleared once driving. The intercooler on mine was full of oil.

It may be that the smoke and misfire are not related and are coincidence but the low pressure test reading does point to HG or valve spring/seating problem. I would redo the pressure test to make absolutely sure. I normally remove all plugs so engine spins at max speed. If its the same then further inspection of head/valves I think is required. It may be that the valves on the cylinders that are low and lower are carboned up so not making a good seal especially c3 or as said weak broken springs. Check the coolant level plus check for any signs of oil/bubbles in coolant.

Alasdair

Thank you for your help and suggestions. Ill give tries this week and update when I get new information

Do a dry compression test and note readings. Then add a little oil to each piston and do another. If the results are a good bit higher after oil it may be a piston ring problem. If nothing changes much then its probably HG or valves. Hope its something fairly simple. Have had broken spring on valves before and got misfire plus very low compression. Garage managed to repair with head in place. They fed soft string into sparkplug hole and turned engine over carefully and using piston to jam valve and managed to compress spring to replace.

Alasdair

16 minutes ago, Alasdair1 said:

Do a dry compression test and note readings. Then add a little oil to each piston and do another. If the results are a good bit higher after oil it may be a piston ring problem. If nothing changes much then its probably HG or valves. Hope its something fairly simple. Have had broken spring on valves before and got misfire plus very low compression. Garage managed to repair with head in place. They fed soft string into sparkplug hole and turned engine over carefully and using piston to jam valve and managed to compress spring to replace.

Alasdair

How much would you say to add to the cylinder? 5 to 10ml?

All you want is sufficient to provide a temporary seal around the piston rings - say one or two squirts of an old-style oil can per cylinder.

Too much oil in a cylinder will give misleading readings, and in worst case, could result in hydro-locking cylinder.

Edited 12 April12 Apr by Warrior193
added information

4 minutes ago, Warrior193 said:

All you want is sufficient to provide a temporary seal around the piston rings - say one or two squirts of an old-style oil can per cylinder.

Too much oil in a cylinder will give misleading readings, and in worst case, could result in hydro-locking cylinder.

Ah so basically a thin film just to line the walls

UPDATE:

This morning i have followed the advice given in the previous messages. After removing all spark plugs the PSI across the board went as C1-152, C2-152, C3-25 and C4-115. After getting the readings i then did the oil test and no change in pressure so thankfully think its not rings or sleeves. Highly unlikely but could it be an injector? After removing the compression tester on C3, on all occasions it came out pretty sodden with fuel.

Something is definitly not right with c3. If it was the rings etc you should have had an improvement. Reckon HG has gone on c3 and maybe tracked slightly to C4. You could try a pressure leak down test to see if you can hear compressed air leaking or guage drops quickly. Each cylinder at TDC and I think its around 100psi From memory there is some normal air leakage of around 10% but with those readings unless its a valve spring I reckon head has to come off. Another thought before removing head is try some soapy water around inectors etc and look for bubbles when cranking just in case its leaking there but think it would be noticeable with the low pressure readings.

Alasdair

2 minutes ago, Alasdair1 said:

Something is definitly not right with c3. If it was the rings etc you should have had an improvement. Reckon HG has gone on c3 and maybe tracked slightly to C4. You could try a pressure leak down test to see if you can hear compressed air leaking or guage drops quickly. Each cylinder at TDC and I think its around 100psi From memory there is some normal air leakage of around 10% but with those readings unless its a valve spring I reckon head has to come off. Another thought before removing head is try some soapy water around inectors etc and look for bubbles when cranking just in case its leaking there but think it would be noticeable with the low pressure readings.

Alasdair

With regards with HG when testing i did keep all sparks removed and removed all caps off the engine to allow pressure release which it didnt drop. I will try the injector trick you mentioned just to be on the safe side but am thinking more and more its valve related.

Valves, head or gasket issue - head removal needed in all cases.