Hi I have a 2003 1.2 6v 120000miles fabia, for a while now occasionally the EML has come on usually at the beginning of a long journey but goes off after 100miles, I have a cheap reader the code is always the same P0420 I thought the cat was on it's way out. But I have realised why this happens at the beginning of a long journey I always top up the oil before I set off on a long journey.

So I'm guessing that I'm burning oil which increases the emissions and throws a cat warning, after I've burnt enough to lower the oil level/pressure it stop burning oil and the light goes out.

Is this a known issue what do you think would cause it worn vavle stem oil seals or something simple like PCV or EGR.

Thanks Haydn.

Won't be EGR, you don't have that.

Have a look at Torbo's recent thread, worn piston rings seems to have been the main problem with his, I think.

Thanks I don't think it's piston rings I've not had any loss of power and it starts on the button. Ive had it 4 years and I'm still surprised how well it pulls.

I have a compression tester in the back of the shed I'll test the cylinders on monday

Good plan. Oil burning could easily be stem seals, but I'm not clear how it could be related to oil level in that case, as the same amount of oil is pumped up to the head whatever the sump level, as long as there's enough to cover the pick-up?

An increase in crankcase pressure leads to greater oil consumption via the valve guides, it is possible that the lower oil level increases the crankcase void volume sufficiently to alleviate this problem. My money's on worn valve guides and aged stem seals exacerbated by a reduction in PCV efficiency.

Edited 26 March, 201610 yr by sepulchrave

Yeh sounds like it could the cause. Next question can the head be reworked at home or is a recon head required. MOT is next month if it fails emissions the car might not be worth spending the money on.

I think the head must off in any case. But its a good plan you have to to check the compression, but also the cylinder leak (leak down with air pressure).

The valve seams is not the best i have seen. I think you have to change them and the seals. 

Thats the minimum. 

In the same operation you have to change the timing chain and may be the chain for the oil pump? 

Also: Head gasket, exhaust manifold gasket, exhaust gasket from the catalytic and some other floating gasket. 

The seal for the crankshaft is also a must. The original is bad, without spring/feather. 

I also changed one valve. Thats I remember... Check my link....?

 

When I have done all that thing the engine was better, but not good enough for me. Its still used some oil, but less. So I had to go down in the engine...

chesk also the spark plugs first. 

Thats not easy...

 

After the head is of, take a good look at the top of the piston. Color, oil and check the cylinders for wear.

Some picture will tell some in here more.... 

Yeh sounds like it could the cause. Next question can the head be reworked at home or is a recon head required. MOT is next month if it fails emissions the car might not be worth spending the money on.

 

Recon head required.

Thanks for the replies. Cost of a recon head and all the bits to fit it isn't far off the value of the car so I hope I don't have to.

I've done a bit of reading on polo forums and it seams a faulty PCV can make an engine slurp loads of oil. So I'm going to check this out first as it's cheap and easy.

Coincidently I replaced the PCV breather/vacuum hose last year as it was split. I replaced it with normal hose that just collapsed under vacuum so I swapped it for reinforced hose which seemed to work. I was surprised at the time as the original wasn't reinforced. So it seams there was something wrong back then and I didn't notice.

We can hope the best! May be Wimo has a good contact to recon the head? 

 

It is a lot of job to change to, and special tools... 

Edited 27 March, 201610 yr by Torbo