Is it a worn engine

[bluest2]

We have a 51 reg Seat Ibiza with about 45,000 miles on it. It has the 1.0 Mpi engine, the same as used in some Polos, Lupos, Arosas etc.

The problem is every year or so (it's happened twice now) the engine management has a hissy fit and goes into fault mode. The result is poor idle, loss of power and MOT failure due to emissions. On both occasions the garage have reported the problem as dirt in the throttle body, which they have cleaned out and then reset the fault codes. The car then runs good as new.

My concern is why is this happening? When I service the car, I always find quite a lot of oil in the airbox and on the throttle butterfly. I guess it is coming from the breather, but why? The car has always been serviced correctly, except it may have missed one year and done 20,000 between oil changes (it could have been done and not stamped).

I'm assuming the problem is bore wear or some such but wouldn't have thought one missed service could cause so much damage. Is there anything else likely to be causing it, or anything that can be done to stop it? Purveyors of magic gloop need not apply

If I have to I'll clean the throttle body regularly myself but am concerned about disturbing it as it's a fly-by-wire jobby. If I move the butterfly will I confuse the ecu? Anyone know the best way to go about it?

[SneakyNeil]

Just a stab in the dark but it might be worth checking/replacing the PCV valve if you've got one on your engine. If it's blocked the blowby could be ending up in the airbox rather than downstream of the throttle.

Edited by SneakyNeil on Friday 10th August 15:37

[Trooper2]

SneakyNeil said:

Just a stab in the dark but it might be worth checking/replacing the PCV valve if you've got one on your engine. If it's blocked the blowby could be ending up in the airbox rather than downstream of the throttle.

Edited by SneakyNeil on Friday 10th August 15:37

check/ replace the PCV or if not equiped, the breather tube[s], some times these breather tubes can collapse forcing oil into the intake system.

[bluest2]

What does the PCV do, and where might I find it?

The breather tube are ok if a little oily inside. The oil appears to be entering the airbox via the breather tube.

[Trooper2]

Here is what it does:

http://en.wikipedia.org/wiki/PCV_valve

It's normally located somewhere on the top of the engine, usually on the rocker/valve cover. If you have already found the breather tube(s) follow toward the engine and if your vehicle has a PCV you'll find it at the end of the breather tube, probably plugged into a rubber grommet.

[bluest2]

Thanks. it all becomes clear...

I''m pretty sure there is a small vacuum pipe that runs from the rocker cover to the air cleaner but I can't recall the exact arrangement of pipework off the top of my head. Due to the big plastic shield manufacturers like to put over the engine I'll have to wait until i've got time to remove it to have a look.

[SneakyNeil]

Generally theres usually a connection from the manifold to the cam cover with the pcv valve in it, and a connection from the cam cover to the inlet tract after the filter. Normally the manifold vacuum pulls crank gasses through the pcv into the manifold to be burnt. The second connection to the intake pulls clean air from the inlet through the engine if a vacuum forms inside the engine because the pcv sucks more than the rings blow. If the pcv is blocked/not working though the blowby isn't sucked into the manifold, pressure tries to build and its pushed back up into the intake tract oily mist and all.

The valve its self is a little flappy spring thing, at idle & light load the high vacuum pulls it closed it to prevent the extra oily gasses affecting the way the engine runs. Under load the vacuum is less and allows the gasses to be pulled through. At least I think thats what *should* happen

HTH
Neil

[bluest2]

I think I have a rough idea of how it all should work, but am still a little confused about how many hoses there should be, which one should flow air in which direction etc. I have ordered one of the VAG factory workshop manuals on DVD off Fleabay in the hope it will help. I still haven't had chance to take the airbox off the top of the engine for another look.

As far as I can remember there are three hoses feeding into the airbox/filter assembly. One is small bore, comes from the top of the rocker box, doesn't look to have anything like a valve in line with it. There is another small bore one that I can't remember where it goes, maybe to the side of the cylinder head somewhere.

The third is quite a large bore, comes from down the back of the block, under the inlet manifold somewhere. This is the one that seems to deposit all the oil in the airbox.

As soon as I have chance to have it in bits again I'll be back on for more advice.

Thanks for your help, everday's a school day.