Recently changed the complete engine in my 2.5TD Omega (inc. Diesel Pump etc.) with a low mileage one. Since changing I have began to have a problem with the idle. First 7-10 miles there is no problem, but then when fully hot it starts to have idle problems. It never cut's out, but starts chugging / hunting - feels like a cylinder is not firing. If left for 20 seconds or so, or with a quick blip of the throttle it begins to clear and then idle's perfectly. Then following driving again and returning to idle it continues to do this!
When actually being driven the car never misses a beat and runs very smoothly.
I've looked at the EGR Valve and ensured this and the inlet manifold has been cleaned with no gunk inside either. I've read elsewhere that a faulty EGR Valve can cause idle problems by being open at idle when it shopuld be closed? How do I blank off the EGR Valve or check if it is indeed stuck open at idle?
I've also read elsewhere that there is a potentiometer on the pump (part of the drive-by-wire throttle system) that may need a clean. However, after looking at the pump I'm not sure where this is - could be inside and require the top cover taking off which I'm nervous at doing in case I cause any other problems to what can be a potentially troublesome pump on these cars.
Can anyone offer any advice please?