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2008 3.0TDI (CAPA) rough idle on cold start

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1K views 7 replies 4 participants last post by  maloyutu  
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#1 · (Edited)
Hello to everyone!

I have 2008 Audi A5 coupe with 3.0TDI CAPA engine and manual transmission. Lately I have had issues on cold starts, car has random violent shakes (sitting inside I can feel it pretty good, door open I can see the door shaking a little bit also). No fault codes. Seems like it is getting a little bit worse every time. It fades away when car gets warm and after that it seems to work flawlessly. If I drive it when the engine is cold I cannot feel the shaking, only when sitting idle.

I have done some maintenance, fuel and oil filter, new oil, no changes. Also added a injector cleaner to the fuel, seems to have zero influence on the problem.

I'm not sure about DPF and EGR but it seems like someone has removed them. No wires going to EGR. DPF is visually still on the exhaust but it has had 0 faults and 0 burning. Maybe someone has drilled it, not sure.

Also checked the injection quantity variations on VCDS. On cold start the highest value was on cylinder 5, it had 1.2mg/stroke and lowest value was on cylinder 3, -0.6mg/stroke. Other cylinders were closer to the zero value. These values are not exactly perfect but it seems like these are fine and not the cause for the problem. I might be wrong also, don't know what the 'ideal' measurements are.

Can it be the PCV valve fault? How to diagnose if this is faulty? I took the intake off on the summer, and it had a little bit of oil inside it.

Any suggestions are welcome, I also have VCDS so I can check needed parameters. Car does not have any fault codes related to the problem.
 
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#3 ·
Issue still exist, don't know where to look anymore. Also noticed that engine has slight but steady vibration also somewhere around 1800RPM, holding still. Doesn't matter if engine is up to temp or not. Also not sure but seems like when engine is cold it becomes little bit smelly outside. Can't describe how it smells, just like exhaust fumes but hits 2x harder 😄

Can maybe some vacuum lines or something like this cause my issues? Maybe there are some values I could check in VCDS?
 
#4 ·
Here is the diagram of the EGR for your engine, just because it's not plugged in with no codes doesn't necessarily mean it's been mapped out correctly either. As you have no reconigtion of what's been done to the car it's a adventure down the rabbit hole.
The EGR is controlled by a vacuum solenoid number 45, if that's activated or it's failed in the open position you might have a vacuum leak
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#5 · (Edited)
I would rather suspect the timing chain. When the engine is cold and idling there is a lack of oil running through all kind of systems. The chain guides and spanners are oil operated, a streched chain will be most noticable at idle on a cold start as the spanners are not pushing the chain in position.

A broken pcv valve will whistle like crazy, I don't think that is the problem.
 
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#6 ·
Thank you guys for ideas!

Vacuum leak sounds like something that could be the reason for all this. Any good ideas how to check solenoid or replacement only shows?

About timing chain, wouldn't it rattle like crazy? I don't have heavy rattle issues, tbh it rattles very rarely, and if it rattles, it lasts maybe a second. I had good VAG specialist take a look once at this, and he told me that CAPA shouldn't have timing chain issues. I don't remeber specifics on this story, but he told me that if it starts to rattle, then engine is most likely in a need of a oil change. Has worked to this day :D
 
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#7 ·
Update: Seems like EGR solenoid is not a issue, but it was worth a shot. What I did: took it off the car. The remaining vacuum lines on the car I plugged with some screws to make it air tight and issue still exist in the mornings. Actually even gave me a engine light, so seems like everything works in that department..
 
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