I'm struggling with my TD4. When I go to start it she cranks and goes to about 500rpm and sits there with the starter still trying to crank and there is no accelerator response. No errors are generated. We've checked the pullies and she does it with or without the belt on.
Any ideas as to what it could be? I did replace the throttle body with a generic part in March. Could that be the problem? Air filter and intercooler are clear as well

500 RPM suggests there's no compression. Normally these engines crank at about 250 to 300 RPM.
When was the timing belt last changed? Hyundai Ioniq 5 Ultimate. The family car.
2009 Rimini Red SE TD4. Gone.
2006 Tonga Green i6 HSE. Gone.
Audi A5 convertible, my daily driver.
1972 Hillman Avenger GT, the project.