skoda octavia vrs petrol 61reg - engine judder

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Sun 8 Feb 2015 16:12
skoda octavia vrs petrol 61reg - engine judder - sammy1

Dealer has renewed injector cyl 3 after stuck open sudden failure, no problems before.

Engine is now juddering, dealer has cleaned all injectors checked coils plugs

wiring loom to injectors compressions, plugs and emmisions. NO codes are appearing on diagnostics.

The rev counter is rock steady but car is hesitating on the throttle

Any ideas please

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Mon 9 Feb 2015 08:22
skoda octavia vrs petrol 61reg - engine judder - Railroad.
First. Just because there are no codes does not mean there are no faults. A fault code will only be generated when a component is open or shorted to earth, or when something is causing a sensor or component to be operating outside the programmed parameters of the ECM.

If an injector was stuck open as you say then the obvious thought is a hydrolock. The incompressible fuel which would have entered the cylinder uncontrolled may well have caused some damage, and quite likely caused a con rod to have become bent resulting in s loss of compression. Keep on at the dealer. You just cannot ignore a stuck open injector and pass it off as trivial.
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Mon 9 Feb 2015 12:19
skoda octavia vrs petrol 61reg - engine judder - sammy1
First. Just because there are no codes does not mean there are no faults. A fault code will only be generated when a component is open or shorted to earth, or when something is causing a sensor or component to be operating outside the programmed parameters of the ECM. If an injector was stuck open as you say then the obvious thought is a hydrolock. The incompressible fuel which would have entered the cylinder uncontrolled may well have caused some damage, and quite likely caused a con rod to have become bent resulting in s loss of compression. Keep on at the dealer. You just cannot ignore a stuck open injector and pass it off as trivial.

Thanks for reply dealer did thorough check on compression all cyl OK.

dealer seems to have checked electric side any thoughts on fuel mixture and

censors which control it?

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Mon 9 Feb 2015 15:55
skoda octavia vrs petrol 61reg - engine judder - Railroad.
Another possibility could be wear in the affected cylinder bore due to the lubricating oil being washed off as a result of the stuck open injector. As I said before, this cannot be simply brushed off.

In answer to your question the fuel system is 'closed loop'. This means that put simply the ECM receives information from the pre-catalyst oxygen sensor and then reacts to that information. In order for the catalyst to work and convert harmful gasses into those that are not harmful the ECM needs to run the engine in both a rich and lean condition. The catalyst needs carbon monoxide which is produced by a richer mixture, and oxygen of which there is more when the mixture is lean. Halfway between the two is what we call the stoichiometric, or the chemically correct mixture of 14.7 parts of air to 1 part of fuel. The ECM runs the engine rich until the O2 sensor tells it so, and then it runs lean until the ECM tells it so. This continuous switch between rich and lean can be seen using a scantool, and is what we call closed loop.

Fuel trim is the ECMs correction functionality. If the engine is running predominantly rich then the fuel trim system will take fuel away, and the opposite is the engine is running lean. Short Term Fuel Trim shows the running state of the engine. A positive percentage means the ECM is adding fuel in response to a lean condition. A negative percentage shows the opposite. Long Term Fuel Trim is the ECMs response to STFT.

Checking the fuel trim on your car will tell you whether you have a rich or lean condition and what the ECM is doing to correct it. This is a very useful tool for helping you to diagnose faults.
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Tue 10 Feb 2015 21:17
skoda octavia vrs petrol 61reg - engine judder - sammy1

To Railroad Thanks for info on fuel open and closed loops.

Have managed to establish that car is reverting to open loop from closed when up to temperature.

temp sensor or lamda o2?? what would you think?

back to dealer

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Tue 10 Feb 2015 22:26
skoda octavia vrs petrol 61reg - engine judder - Railroad.
Could be. I doubt that being soaked in neat fuel would've done the O2 sensor much good.
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Wed 11 Feb 2015 18:40
skoda octavia vrs petrol 61reg - engine judder - elekie&a/c doctor

Mr RR's info is spot on,however this is an Fsi engine and the fuelling strategy is different to a conventional efi system.The car has air/fuel ratio sensors rather than lambda sensors as the values can vary far in excess to a normal system.As this is a direct injection system ,you may find that there is a build up of crud in the inlet manifold causing your problem,as the air inlet tract does not get washed by the fuel injectors.Late model Minis and Bmw are suffering this problem.

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Sat 14 Feb 2015 16:19
skoda octavia vrs petrol 61reg - engine judder - sammy1

took car to independant vw who dianosed oil in cylinders 2 and 4 and possibly interfering with combustion hence judder.

car not using oil prior to injector problem but since oil change at time injector

was changed used litre in 1800miles.

Pressure test on cylinders all ok

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Fri 20 Feb 2015 16:33
skoda octavia vrs petrol 61reg - engine judder - sammy1

still judder on medium acceleration also have a long term fuel trim LTFTof

minus 14 per cent which indicates fuel is running a rich mixture and smell of petrol under bonnet.

Still unable to identify the prob

Tried Terraclean on both air intake throttle flap/body and engine itself

intake manifold and valves, so hopefully carbon build up ruled out

Looking now to possible faulty air or cooling system sensor as cause

Any help comments appreciated

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Fri 20 Feb 2015 18:30
skoda octavia vrs petrol 61reg - engine judder - Railroad.
A long term fuel trim of -14% is certainly not acceptable, and you are correct in saying that the engine is running rich, and that the ECM is compensating by shortening injector duration in order to inject less fuel in response to the rich condition. The question now is why?

I can't help thinking that an injector could still be the cause, or an injector wire to the ECM chafing to earth causing an injector to open when it shouldn't be open. Could that have been the cause of your stuck open injector? Fuel injectors themselves are very reliable, and failures are rare, but that's not to say they've never failed or never could fail. Other possibilities include a restriction in the fuel return or a stuck closed fuel pressure regulator. Has your garage checked the fuel system pressure? Check the whole air intake system and change the air filter too.

A faulty O2 sensor could also be the cause. Test the upstream sensor by monitoring the STFT with a scantool. Then pull the dipstick out which on these engines will create a vacuum leak. The STFT should immediately start increasing as the ECM adds fuel in response to the lean condition, and consequently in response to that the LTFT should start to decrease. If there's little or no change you should suspect the sensor is faulty.

Edited by Railroad. on 20/02/2015 at 18:41

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Fri 20 Feb 2015 21:36
skoda octavia vrs petrol 61reg - engine juddering - elekie&a/c doctor
Replacement of the injectors on these requires removal of the inlet manifold .It is possible that an o ring joint is leaking air or the new injector seals have not been fitted correctly.(special tool reqd)
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Sat 21 Feb 2015 09:28
skoda octavia vrs petrol 61reg - engine juddering - Railroad.
Replacement of the injectors on these requires removal of the inlet manifold .It is possible that an o ring joint is leaking air or the new injector seals have not been fitted correctly.(special tool reqd)

That is indeed possible, but it should show up when testing fuel pressure which would be lower than it should be due to the leak. Also the spark plug on that cylinder would be blackened compared to the rest, which would show signs of excessive fuel.
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Sat 21 Feb 2015 10:08
skoda octavia vrs petrol 61reg - engine juddering - sammy1

to Railroad thanks for responce. I tried the dipstick Pulled it when warm.

immediately the STFT went to Plus 25% after 10s dropped back to Plus 10%

and then to +/-0.8% in 30s.

When I put the stick back in stft went negative 25% and dropped to 0%

after 30s

There was no change to LTFT Test took about 5 mins.

Any conclusions?

For your info Skoda did the injector and as far as aware did necessary tests.

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Sat 21 Feb 2015 10:26
skoda octavia vrs petrol 61reg - engine juddering - Railroad.
Yes. The obvious conclusion is that the air/fuel ratio or O2 sensor is functioning correctly. The engine is clearly running rich, the cause of which needs to be identified. The fuel injector leak possibility is a good one, and I think that's where you should start.
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Sat 21 Feb 2015 10:51
skoda octavia vrs petrol 61reg - engine juddering - Railroad.
There are two STFT figures and two LTFT figures on VAG vehicles. One is for idle and one is for partial, or under load. You are not likely to see a change in the LTFT partial figure until the car has been driven. However, if it's operating in closed loop you should've seen a change in LTFT idle as the ECM responds to STFT idle. VCDS is the best diagnostic tool to use for this. What are you using?
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Sat 21 Feb 2015 10:54
skoda octavia vrs petrol 61reg - engine juddering - Railroad.
Also do not forget that clearing the fault codes irrespective of whether or not any codes are stored will reset the fuel trim information. Be sure to do this when the cause for the rich running condition has been cured, otherwise you could easily be led up the garden path.
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Sat 21 Feb 2015 13:36
skoda octavia vrs petrol 61reg - engine juddering - sammy1

to Railroad Thanks again Car is booked back into Skoda Monday, 7th visit!

maybe with your input and best German tech will finally solve my problem.

For your info my cheap OBD is only recording single digit misfires on all cyl.

Will report outcome here for your interest.

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Sat 21 Feb 2015 16:07
skoda octavia vrs petrol 61reg - engine juddering - Railroad.
Search the VAG forums for anyone near you with VCDS. I have, and I'm in Hampshire if that helps. Try the Skoda forum at www.briskoda.net and look on the Diagnostic and VCDS forum.
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Tue 24 Feb 2015 18:40
skoda octavia vrs petrol 61reg - engine juddering - sammy1

Car went into Skoda Monday for another shot at diagnosis. conclusion all within set parameters.

Car is still juddering on tickover and mild acceleration.!!

My OBD reports single figure misfires in 25 mile mixed driving

I tried monitoring my lamda O2 sensor but do not understand the readings

bank 1 sensor 2 active o.56volts

0.1 to 0,8 when moving

No other sensors or banks reporting as active

Does anyone know standard reading to compare or comment please

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Wed 25 Feb 2015 08:22
skoda octavia vrs petrol 61reg - engine juddering - Railroad.
Bank refers to a group of cylinders. Bank 1 is the first bank, and Bank 2 is the second. Your engine is inline and therefore only has one bank. V engines have two banks, and oxygen sensors for each bank.

Bank 1 Sensor 1 is the pre-catalyst O2 sensor on Bank 1.
Bank 2 Sensor 1 is the pre-catalyst O2 sensor on Bank 2 ( V engines)
Bank 1 Sensor 2 is the post-catalyst O2 sensor on Bank 1
Bank 2 Sensor 2 is the post-catalyst O2 sensor on Bank 2 (V engines)

The O2 sensor on B1S1 should range up and down between 0.1v and 0.9v as the engine switches between running rich and lean. The midway point is 0.45v and represents the stoichiometric where the air/fuel ratio is correct at 14.7:1. The ECM responds to information received from the sensor, and this is known as 'Closed Loop'.

The O2 sensor on B1S2 is only really there to tell the ECM that the catalyst has done its job. Its voltage reading should not range up and down, but remain fairly steady. A faulty or misreading B1S2 is very unlikely to cause any engine running issues since the ECM does not respond to information received from it.
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Wed 25 Feb 2015 14:45
skoda octavia vrs petrol 61reg - engine juddering - slkfanboy

I have had a faulty O2 sensor and it's caused much the sme issue as you are having. Mine was after a cam belt failure and engine rebuild.

The reading you have are one of two thing one the O2 sensor and 2 Air leaking into manifold after the MAF. The MAF calc's how much air is required and the O2 sensor trims the mixture. so the S term trim reading should go to zero after time and adjust the long term readings as I understand it.

I would replace the O2 sensor as a matter of course

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Wed 25 Feb 2015 19:57
skoda octavia vrs petrol 61reg - engine juddering - sammy1

hello Railroad no further advanced

Could you please explain why I cannot get a reading on

Bank 1 sensor 1 ie the sensor BEFORE the cat

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Wed 25 Feb 2015 23:05
skoda octavia vrs petrol 61reg - engine juddering - Railroad.
If the sensor is either open circuit or short circuit then a fault code to that effect would be generated. If the sensor was not producing a voltage then I'd suspect it was faulty, since the sensor produces its own voltage. Zirconia type sensors are sensitive to oxygen. They measure the difference between oxygen inside the exhaust and oxygen outside. Rich mixtures consume more oxygen than lean mixtures, and so a high voltage means a larger difference between inside and outside, and a rich mixture. A lean mixture is the opposite. I thought you said earlier that it had a good reading, ranging up and down from 0.1v to 0.9v
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Thu 26 Feb 2015 09:29
skoda octavia vrs petrol 61reg - engine juddering - sammy1

To railroad Sorry but still do not understand

If bank 1 sensor 1 is the pre cat before NOT REPORTING

bank 1 sensor 2 is the post cat after, giving the voltages

Then only the post cat is giving the voltages reported when the pre cat seems to be the important one

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Thu 26 Feb 2015 09:53
skoda octavia vrs petrol 61reg - engine juddering - Railroad.
The ECM responds to information received from B1S1 once the sensor is warmed up and working, and the fuel system is in Closed Loop. Your scantool should be telling you that the fuel system is in CL. If it stays in Open Loop then maybe B1S1 isn't working.

You also told me that the Short Term Fuel Trim figure changed dramatically when you pulled the dipstick and created a vacuum leak. That means the ECM was responding to the artificially created lean condition by adding fuel. This suggests very strongly that B1S1 is working as it should be. The ECM doesn't actually know you pulled the dipstick, it only recognises a lean condition based on the information received from B1S1.

I think you'd be well advised to find someone with VCDS to help you with this. It's much more powerful and specific than a generic EOBD scantool.
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Wed 4 Mar 2015 23:05
skoda octavia vrs petrol 61reg - engine juddering - sammy1

car back to Skoda today still no diagnosis not coding.smell of fuel and low rev judder

Took car to old school independent who did smoke test on manifold all OK

Also mentioned very slight wisps on injectors 1 and 2. which he dismissed.

Found that the the PURGE valve when operating and throttle depressed

purge valve does not shut down until 3000rpm thus delaying a stable

manifold vacuum. I read that when car is on and off the turbo gases are

directed two different ways. there is another valve controlling this.

If these valves are not working could they cause my symptoms fuel smell in particular .

Also could the injector failing open cause these valves to fail because

either the failing injector has knocked something else out or SKODA has bad workmanship

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Wed 11 Mar 2015 16:04
skoda octavia vrs petrol 61reg - engine juddering - sammy1

Back to skoda today

Removed injectors at my insistance and guess what

NIGHTMARE over, the wrong injector is fitted !!!!!!!!!!!!!!

Thank you too all who contributed

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Wed 11 Mar 2015 16:28
skoda octavia vrs petrol 61reg - engine juddering - Railroad.
Well done mate, your persistence paid off. And you have learned something about modern petrol fuel injection in the process.
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Mon 14 Sep 2015 14:24
skoda octavia vrs petrol 61reg - engine juddering - octavia_vrs20t_John

Good to read, had similar problem with 2010 2.0 TFSI octavia vrs. Came out 4 weeks ago and toke it into main dealers, said they couldn't find anything wrong then because they had been opening the injectors via laptop which makes it run fine for a short while. Problem returned today and VW specialists came out and confirmed injector issue, I should have been more persistent the first time. Hopefully will be sorted tomorrow. The VW guy said better filling at shell as supermarkets have a higher sulpher content that the injectors don't like. Anyway if it hasn't fixed it I'llbe sure to make them change the injectors! Cheers Guys

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