ruff idle 2003 sprinter 2.7 l 5 cyl MERCEDES-BENZ SPRINTER 2-t Box (901, 902)

Had similar on my '04 Sprinter after turbo swap. Turned out one of the injector seals was leaking - not enough to show black around it yet, but enough to mess with idle. Did you check if any injectors are weeping after all that work?

+1 with andrew. Also worth checking MAF sensor readings with a scanner if you have one. Mine was reading too high at idle (~560mg/h instead of 450-480) and caused rough running even though it "worked". Replaced it and ECU started controlling things properly again.

@andrew_taylor Good shout on injector seals. I'd add - check for vacuum leaks around intake manifold gasket mate. When you pulled intercooler and hoses off, easy to not get everything sealed back perfect. Spray some carb cleaner around gaskets while it's idling, if revs change you found your leak.

Might sound daft but have you checked fuel pressure? My mate's Sprinter was doing this - rough as hell at idle, ran okay under load. Fuel pressure regulator was dodgy, caused slight overfueling. No codes thrown either which was annoying.

@WILSON78 I replaced my MAF thinking that was it, didn't help at all. Turned out to be injector leak-off rates way out of spec on cylinder 2 and 4. Cost me £180 for the MAF for nothing before finding the real problem.

Check the injector seals seriously. When oil cap blew off originally that's massive crankcase pressure - could've damaged seals then. Copper washers on those need replacing every time you touch injectors or you get "black death" later and rough idle now.

Did you do any kind of adaptation reset after replacing all those parts? ECU might still be running old parameters. Worth getting it on a proper scanner to check live data - injector balance, MAF readings, fuel pressure.

@PaulRoberts94 Good point. Also @user_63261 when you say rough idle, does it smooth out above 2000rpm? If yes, classic sign of either vacuum leak or one cylinder not firing properly due to injector issue.

I'd put money on injector seals or one injector leaking off too much. You've replaced everything else! Get a leak-off test done - costs like £50-80 at most places and tells you exactly which injector(s) are knackered. Saved me weeks of guessing.

@user_63261 Also mate check your boost pressure sensor connections after all that work. Sometimes just unplugging/replugging things during repairs creates dodgy connections. Mine was loose after intercooler flush and caused surging idle til I pushed it in properly.

Honestly sounds like you've got multiple things going on. Original problem was turbo and oil in system - sorted. Now rough idle after repairs usually means either air leak you created during work, or injector issue that was masked before by the turbo problems. Start with smoke test on intake system, then injector leak-off test.