I have an Octavia II 55plate PD140 with approx 87K miles. Its always been dealer serviced and I have owned it approx 4 months. It has recently started loosing power spontaneously, sometimes on the motorway during a 15 mile commute only when traveling 60-70mph. The engine management light has illuminated once which revealed a code of "over boost pressure". I''ve been through all the usual points like fuel and air filters. The behaviour is similar to fuel starvation but the power never dies completely, you could still manage say 40mph. Would this be an intermittent fault with the air mass sensor? Any suggestions please.

The car is going into "limp home" mode and it could be for any number of reasons. Overboost can be caused by a number of things so we need more info on the fault. It may also be worth checking if the car has, or has had one of those cheap dodgy remap resistor mods on it in the past.

Thanks for the prompt reply. Have looked at the fault code again from my U281 memoscanner. It shows fault code 16618 Boost pressure regulation ; limit exceeded (overboost condition) ; P 0234. I am not aware of any alterations prior to obtaining the car but it was 1 owner which was a limited company ALD Automotive from Bristol. Where would the resistor be located and is there an easy way to identify if it has been changed say by a visual inspection. Chris

If the car has a 'Resistor Mod' then it will be plugged into the sensor set into the air intake hose - after the air filter.

You will need to remove the plastic engine cover - pull up at the front and then forward to free the rear mounts - and look on the RHS of the engine bay.

It will be obvious if there is one fitted - either a largish black right-angled box or a plug with 2 wires in it running to a seperate box probably placed in the battery box.

If you have one, simply remove it and plug the original black connector back into the intake sensor.

Have checked engine bay there are no extra resistor boxes etc. What further info is required pse re the diagnosis. Chris

I doubt that it is the MAF (air mass sensor).

I guess the two most likely causes would be a damaged hose or a faulty boost pressure control valve (aka N75).

I suggest you PM lummox. He's a couple of miles down the A509 from you in Easton Maudit.

IIRC, ALD Automotive is a fleet management company. Many of these companies will email you the cars complete history if you speak to them nicely. Every previous fault, service, etc will be in their computer.

Overboost.... sounds like a sticky turbo to me.

Yes I agree that it may be to do with the turbo. I got the overboost error code just before my the turbo went on my 140bhp Touran.

I think there is a problem with the variable geometry.

If the geometry can not be controlled in proper way, the turbo would go in overboost situation.

Edited 18 January, 200917 yr by chavdarlk

I'll vote for sticky variable vanes on the turbo as most likely (and mentioned already by others).

The most common symptom is a sudden loss of power when accelerating through 2,000rpm or so or when pressing harder on the accelerator to go up a hill. When you switch the engine off it is fine again (until the next time). This seems to happen more often to cars that are normally driven fairly gently at lower revs, as the vanes seem to stick in the low rev position. As the revs come up the vanes can't move to the high rev position so the ECU sees too much boost so it goes into "limp home" mode to protect the engine.

If this is the fault with your vehicle it is possible to free the vanes up much cheaper than just replacing the entire turbo (which is what most dalers will want to do). Heaps of info on this available by searching the web, but if you have to dismantle the turbo it is a pretty messy job (only for the really enthusiastic DIYer I'm afraid).

PLease let us know what the fault was and how you get on (it adds to the collective knowledge and helps us provide better advice to people such as yourself in the future).

Thanks for your info on the matter. I have to say being connected to the motor trade some years ago gaining the required City & Guilds etc and dealing with the "old technology diesels" the thought of a turbocharger with variable pitch blades takes some thought on how they would be actuated. Would the variable blades be on the exhaust side or inlet side, the exhaust would seem a nightmare to actuate in view of the temperatures involved. Or is this simply an example of a sticking "waste gate" on the turbo unit. Your suggestions re the fault developing does seem the most credible although access to the turbo charger for investigation in the first instance is less than ideal. Will keep you informed.

I had the overboost fault P 0234 on my MK1 octy. The problem was the turbo vanes sticking, the car was OK when I reset the ignition for a while.

This might help

http://pics.tdiclub.com/data/500/Drivbiwire_VNT_repair_procedure_small.pdf

Many thanks again. I now see exactly what a variable vane turbocharger is. have to say its something that will get seized up moreso than not. Any way am awaiting contact wether a "good will contribution" will be forthcoming from Skoda as the car has been fully serviced from new.

Mine went at 63k and Skoda UK replaced it at 50% of the normal cost of parts & labour.

Turbocharger is £1070 plus labour and VAT etc. Good will gesture of 50% leaves cost at £900 which is v. high for a car with 84K. Will have to check the options but thanks for all your help the forum has been invaluable.

The vanes are on the exhaust side. It can sometimes be a fault in the actuating mechanism rather than the variable components. It is a lot cheaper to have the vanes cleaned up and freed by a turbo specialist rather than fitting a totally new turbo from Skoda. Sometimes people have managed to free up a "slightly sticky" turbo by manually pushing on the actuating rod (but I gather it is pretty hard to do).

A common way of preventing the problem from re-occurring (once they have been properly freed up) is to give the engine full throttle in 2nd or 3rd gear, starting at 1,500rpm and going through to 3,000rpm (traffic permitting). This will force the vanes to cycle through their full range of motion, thus stopping them from sticking in one position. I try to do this about once or twice every hour or so of driving on my TDI (and it can be fun too )

Turbochargers are approx £348 exchange recon and £488 new all plus VAT. On looking at the link to the tdiclub from moley above it gives you a clear picture of what happens and I will most likely take that route first (thats if I can not cycle them via your process first)

Mates Seat Altea had this code.

Took it to Seat who said it was OK.

Week later turbo, let go.

I took a Vag COM Reading.

1 Fault Found:

16618 - Boost Pressure Regulation: Limit Exceeded (Overboost Condition)

P0234 - 000 - -

Freeze Frame:

RPM: 3087 /min

Torque: 334.0 Nm

Speed: 72.0 km/h

Load: 96.9 %

Voltage: 14.21 V

Bin. Bits: 00101000

Absolute Pres.: 2244.0 mbar

Absolute Pres.: 2590.8 mbar

This was the moment recorded when the Impellor shaft broke off, sending bits of impellor in to the intake, where they were mashed up agaisnt the pistons and valves.

The impellor shaft exposed the high pressure oil feed to the turbo and this passed a substantial amount of oil in to the intake. (It was dripping out of the exhaust).

On stripping down what was left of the turbo, the vanes were stiff but not completed inoperable.

If you get this code, IMHO, dont mess about, get the turbo off, get it cleaned and or exhange for an new turbo unit.

The turbo let go on the congested motorway and his missus was driving it, she heard the noise but kept driving until she could get to the hard shoulder. Probable why the damage was so extreme.

It took us a week to strip the whole engine, flush all the galleries, clean the intercooler, replace with all new tubing on the intakes, placed the cats in a bucket of turpentine, which disolved most of the oil. Reassembled with new turbo (£500ish), cranked the engine over without fuel until oil pressure seen. Fired up first time ~(very smokey). Ran the car in again for 500 miles.

Runs okay now, passed MOT emissions (just), so cats are a bit worse for the wear.

I'd say the turbo was on the way out.

My son had a similar fault code with his Seat. It was under warranty from an independent garage and the dealer tested everything possible connected to the turbo system before reluctantly having to concede it was the expensive bit - the turbo - at fault.

My Octavia 11 has just had a new turbo at 104000. When I complained to Skoda they were amazed it had lasted so long! Life expectancy of about 60k (end of warranty time!) but had been known to fail at 20k, was what they said.

I've had a recon unit fitted - basically my old turbo casing with new innards. Only warrantied for one year rather than Skoda's two, but it was about half the price.

I have an Octavia II 55plate PD140 with approx 87K miles. Its always been dealer serviced and I have owned it approx 4 months. It has recently started loosing power spontaneously, sometimes on the motorway during a 15 mile commute only when traveling 60-70mph. The engine management light has illuminated once which revealed a code of "over boost pressure". I''ve been through all the usual points like fuel and air filters. The behaviour is similar to fuel starvation but the power never dies completely, you could still manage say 40mph. Would this be an intermittent fault with the air mass sensor? Any suggestions please.

Best price for supply and fit is £930 from local Skoda dealer and that includes Skoda UK 50% good will contribution. The turbo comes with ex manifold complete plus some oil pipes unlike the reconditioned and other new versions. Also to remove and refit requires the O/S driveshaft removing and the engine moving forwards. It then has a 2 year guarantee! No doubt some special tools will be required so having to bite the bullet and getting it replaced tomorrow.