Intake runners clogging cause

[AutobahnJon]

Have an 04 PD Passat that I'm switching engines in due to a belt failure. The replacement engine had about 2/3 air flow capacity inside the intake runners and head ports which I've scraped out being careful not to damage the valves or guides. I'll use the manifold off the original engine with almost zero obstruction.
1. Is the grime buildup caused by too much idling, lack of oil changes, etc?

2. Does anyone think I should re-use my old injectors while I have the engine(s) apart?

3. Is it possible that the injectors were damaged when my timing belt broke and an injector swap would not be recommended?

Already replaced the timing belt, water pump and adjusters, filters and will drop the pan to check the pump and pickup but it seemed to run nicely before we pulled it from the donor.

Any other words of wisdom will be appreciated.

 

[Mechnurse]

1. This is from the EGR recirculation which carbon/oil mist mix and slowly build up to block the intake runners.
2. The injectors can be reused, how many miles on the engine if its over 100K I would recommend you have them cleaned and balanced. Do you know if there was any biodiesel used or just D2?
3.It's possible but more likely not. The injectors run off of the cam but only compress fuel nothing else

 

[50harleyrider]

Clean biodiesel will keep your injectors clean and long wearing. I'm always so happy in the spring to get back to B100.

 

[AutobahnJon]

Thanks for the info. As the car has been sitting in the garage for a year or so I've cleaned out all the tubing and egr systems not much buildup anywhere on the original. Was just waiting for the winter to end before swapping the engine. Definitely will keep an eye on everything once I get it back together.