Can anyone shed any light on our problem, please. Skoda Octavia Estate 2008, engine no BKD 881718, which is the 2.0tdi 140, 67k miles.

It started as a slight misfire at just above 2000rpm, then developed to being that from above 2000rpm the car would accelerate even if the throttle was held steady, then abruptly cut out and cut back in again. If driven gently at below 200orpm all was fine, although the idle was at times rough.

Took it to the local Skoda dealer, who say they found suspected contaminated fuel which they drained,fitted new fuel filter, but then found uneven injector pressures. Two injectors replaced, problem persisted, then the remaining two injectors also replaced on Skoda UK advice. In the workshop the fault still persisted, and both the dealer and Skoda UK cannot suggest what to look at next.

I then drove the car after the four injectors had been changed - tank empty so first drove the car from a cold start to a filling station - still a rough idle and misfire/cut-outs over 2000rpm. Brimmed the tank with clean fuel, started up, smooth idle, and then drove a fast 5 miles over a twisty road, up and down the rev.range - car like new again. Thought I'd cracked it.

Then turned round to go back to the dealers - rough idle returns, along with the misfire,cutting out, and occasional violent over-revving when foot is off the throttle when changing gear. Back to the drawing board .....

Another forum has suggested a turbo issue – ‘ a total shut down of injectors if the turbo is in an over boost state i.e. the car goes really well then it's like some ones stamped on the brakes. From your description it does sound like a turbo over boost scenario where the vanes are sticking or fractured causing an over boost and therefore shutdown to protect engine from damage.’

But would this turbo-issue also cause the violent over-revving ?

Thanks, Colin.

Edited 16 March, 201313 yr by David 8

Given that the injector seals should have been replaced with the injectors,I would suspect the tandem fuel pump is faulty.

Limp mode shouldn't lead to a rough idle or over revving and once it occurs it doesn't go back to normal until you cycle the ignition.

I made that post a little bigger for you

HTH

Sounds intake related to me, any fault codes?

Sent from my LT26i using Tapatalk 2

Seems that the fuel injection timing is causing the misfires, if its not the fuel injectors then most probably its the fuel pump that needs to be replaced.

Btw does your fuel indicator misbehaves too at times ?

Eventually we have the car back on the road - thanks to Tim at AVW in Caernarfon.   His initial thoughts were that the ECU might be faulty - sent away for testing, and came back 'no faults'.   So he persisted with the fuel system, including replacing the supply pump which was a little low on pressure. Still no change.  So we sent the ECU away again to another tester, ands again it came back 'no faults' .   Tim wasn't convinced, so he shelled out on a £6k machine which allows him amongst other things to switch ECU's between cars - the immobilisers prevent this being possible without being able to temporarily re-programme the ECU.  Then he had to wait until he found a car with an identical ECU - with the customers permission he switched ECU's between the cars, and hey presto - the fault transferred between cars with the ECU.   So, we ditched the old ECU and replaced with a used £400 one - new ECU price would have been £1350.   Car now back in good health, - thanks to Tim and his team.

Great result! Sounds like you've got you've got yourself a cracking mechanic there.