My 2018 TD6 has begun surging, slightly, at idle mostly while cold. The idle typically hangs around 900rpm but it has begun to dip and surge between 900 and 1000 when first fired up. This causes some power loss when you first put it in drive, almost like it starves a little when you first hit the gas but then the problem essentially vanishes. It doesn't ever seem to persist once the vehicle has been driven and starts to warm up. If Occam's Razor holds true, the perpetrator should be the new fuel filter I put on it about 4 weeks ago. The only thing is, though, why would it do that. All the hoses appear to be connected tight and the electrical connection on the bottom (although now missing its metal retaining clip) is snug. Does anyone have any experience installing these? The old one I removed had a hand written torque note on it and I am wondering if maybe the threaded part on the bottom needed to be a very specific torque in order to run properly. I definitely just tightened it by hand.

It could also be my battery which I believe to be the cause of various little electrical gremlins I have been tolerating. Not sure how much the battery would mess with that unless its ****ing with pressure at the injectors. Driving it would spin the alternator, charging the battery and eliminating the issue temporarily? Anyways, can anyone help?

 

It would take serious charging system failure to surge the engine.
Can you measure both fuel pressures?

 

Im going to have to hook up the diagnostic tool because its now progressed. I hit the gas at a stop light today and nothing happened. Very staggered start off the line and only leveled out once I hit 2.5k rpm. It has to be the fuel delivery system. No warning lights but something is clearly wrong. I've got to take the fuel filter out, its the last place I intervened.

 

Ok update, I hooked up my code reader and found a P2BAE00 code which is "limit exceeded" on the NOx sensor. Anyone have experience with this?