Nissan Caravan Engine Running Rich

A rich mixture, especially with those symptoms, does point towards fuel delivery issues. Has the check engine light thrown any specific codes? Have you checked the oxygen sensor or spark plugs?

I haven't checked the oxygen sensor or spark plugs yet. Where would I find the fault codes or is there a way I can check the injectors?

The fault codes can be read using an OBD2 scanner, usually plugged in under the steering wheel. If you suspect the injectors themselves, a mechanic can perform a pressure test. However, considering your symptoms, a defective injector is plausible and going to the workshop would be a good idea.

Thanks. I took it to the workshop. You were right, an injector was defective. Cost me 515€ to replace.