Hello everyone,

Search the internet wide but couldn't find my exact problem.

 

I have 2008 AUDI A3 Sportback 125kW. Couple of months back my fuel injectors failed and were replaced with refurbished ones. Now from time to time on idle the engine shakes a lot, I do hear some sort of knocking noise when it happens but I am not sure if its a misfire or not. ECU doesnt give any error codes what so ever so i am baffled. The shake usually stops after couple of minutes. Now its -10-14C and the shakes starts after driving a little bit then dissapears as engine warms up. I am thinking it could be spark plugs but then ECU should give an error, fuel injectors should give an error as well.

How can i diagnose this? I have Carly OBD thingy for diagnostics so maybe i can look into something with it to identify what is wrong?

I wonder if this could be an engine mount? 

In failing that rough idle could be a failing maf sensor but usually this would show up as an engine light. 

16 minutes ago, Steve Q said:

I wonder if this could be an engine mount? 

In failing that rough idle could be a failing maf sensor but usually this would show up as an engine light. 

Thank you for the fast response.

 

Wouldn't the vibrations be apparent while driving as well if it was the mount? My main guess right now is spark plugs/coil pack?(not sure if diesel has those)? Can I test MAF sensor with the Carly adapter?

Potentially it might depend on conditions. Diesels have glowplugs instead of spark plugs. Definitely check leads. 

A basic test I did with a mad on an old Volvo was to disconnect it t o see how it runs. In my old volvos case the car ran better with the mag disconnected so I knew it wasn't working right. 

Update on this, ended up changing 3 fuel injectors. The shaking is still there on cold start but goes away in 30'ish seconds or less. But now no more smoke is coming out of the exhaust so at least that's good for now. Next up I guess is spark plugs that could be causing the shake on cold start?

Mantas.

Are you really running on your second set of injectors in a few months yet the fault is still present? If so I suspect there is nothing wrong with either set of injectors, and that the fault lies elsewhere. Injectors are extremely reliable and rarely fail.

Please confirm whether your engine is petrol or diesel. The type of fuel is not clear from the above comments.

Please tell us also:

-how many miles (or kilometres) the car has done,

-whether it has been properly maintained during its life,

-whether there are any other symptoms apart from the shaking and associated knocking.