Skoda Yeti 110 Knocking Loudly when the accelerator is pressed down and a light pinking sound when cruising along without speeding up and disappears when on overrun.

 Our Yeti 110 diesel engine has suddenly started to make a loud knocking sound just like pinking on a petrol engine when the accelerator is pushed down to put more fuel into the engine under load.
Tick over is lumpy and improves slightly when the engine oil is hot at around 75*C. If you press the pedal down whilst in neutral without any load then it will rev up ok to 4,500rpm and sounds smooth.  I have connected up a Ross –Tech HEX-V2  to the car and no faults have come up. Unfortunately I do not know enough to see if certain parameters shown are correct or not.The loud knocking sound gets very heavy when in top gear and the engine has to work hard. About two weeks ago we did get some diesel from a Jet petrol station that we normally don’t use and noticed the engine sounded lumpy on tick over with a cold engine? Properly a red herring. Anybody with some ideas on the problem in question as the Mrs dares not to drive it to work with a loud knock that is exactly to the revs of the engine running.

Could be bad fuel as suggested.

 

I understood the engine was protected and should only rev to around 2500 when not under load?

 

Has it had the notorious emmisions fix? That is known to affect injectors, EGR valve, DPF in exhaust etc, all of which can cause it to run rough, although usually you will get a warning light on the dash?

It's not something as simple as the engine cover being loose/vibrating is it?

I have a 2014 110bhp diesel and have owned it from new. It has always done as described above when revved from cold. This is particularly noticeable in the winter. Once oil is up to 90c this does not happen. I believe it is called diesel knock, a form of pre-igntion and is not uncommon in diesel engines. I do not use supermarket fuel, usually filling up at BP or Shell.

I have now done about 33,000 miles. Engine pulls strongly, oil consumption is nill, mpg on a run is up to mid 60's and around town 48/52 in light traffic. My car has had the "fix" and this altered nothing, with exception of more frequent regens and a bit more go at higher revs leading to slightly ? increased fuel consumption. I have had no issues with the car with the exception of one false warning on a throttle position sensor.

 

Colin

 

Edited 27 April, 20188 yr by eribaMotters

@K100RS - If you suspect "bad fuel", why not fill it up with brand name and see if the knocking reduces?

Had an idea over a  coffee looking at the rain pouring down and went out to look at the fuel injector connection plugs that push into the fuel injectors. Took all four off and cleaned them out with a solvent then dried them and pushed  the four back in.

Hey presto lumpy knocking engine suddenly ran smoothly again and took it out for a ten mile run, all back to normal again pulling in all gears smoothly and no knocking.

Can only think after some 110,000 miles the resistance had gone up on the snap connectors somewhere and putting them back in with cleaning had solved the problem. Learn something new everyday.

It will be interesting to know in the next 120 mile run to work if I have actually solved the problem for good.

Yeti has not had the so called mapping fix and you are correct it does stop revving at 2,500rpm in neutral with the limiter on Kenfowler clutch was pressed in and rolling down slope.

Thanks again for your help which got my brain cells working in the rain.

 

Chris