audi A3 BKD engine rough idle difficult hot start

what should i check/replace first on the BKD engine to cure the rough idle? ive checked with vcds and have 2 glow plugs, or wiring to them, that is faulty. also i find it takes quite a bit of cranking when its hot to start it. for now ive patched the idle issue by increasing the idle to 900rpm, though i can still feel the odd misfire.

is there a definitive test procedure/values in vcds to check which sensor is knackered?

i did some googling and found some people have replaced everything from the crank sensor to the fuel temp sensor.

p.s. apparently its had a new starter motor according to the previous owner.

need to test but think it was the battery not spinning the engine fast enough.

misfires? rough idle?

My suggestion is to start by getting values from injector deviations (group 13), to trace any faulty cylinder.

Then a compression test.

the rough idle is probably the exhaust valve timing. ive run diesel purge through it and the deviations have improved, they were pretty good anyway.

I did notice bubbles in the return line though which increased when I revved the engine, so I might have a leaky injector seal.