[NotAMechanic]

Hello everyone!

I have an issue with my 2009 i30 1.6 CRDi. I've searched everywhere and found some similar posts but none of the solutions worked.
When the temperature is below ~15°C, the car always starts flawlessly. However, in warm weather, the RPM keeps dropping and increasing for 5-10 seconds (closer to 5). This only happens if the cars sits for a couple of hours. If the engine runs for a minute or so, the next start is perfect again.
The fuel filter is new and so is the battery. I changed crankshaft sensor, camshaft sensor and mass air flow sensor. I removed injectors and had them diagnosed. They are not perfect but should still be fine. I also checked glow plugs and replaced a defective one without any improvement.
Those were all the clues I found on this and other forums.

This is my first attempt to repair anything in any car so I'd greatly appreciate the wisdom of this forum.

[Vitruvian]

Same problem here (1.6CRDI 81KW 2013. GD). I'm researching for years, but unfortunately it is not solved until today.
All I can say, that definitely has something to do with EGR.
If you put blanking plate to block EGR flow the problem is GONE, but not for long because car always goes in to Limp mode after some time.
I cleaned thoroughly EGR, EGR cooler and intake manifold - it didn't help. I ended up replacing EGR (just mechanic part) with original Hyundai part and the problem is still present...
I think that maybe the problem is in the software that controls EGR or in the ECU itself.