SD4 rough idle

good evening all

I have just had to replace the water pump on my 2011 FL2 SD4

the engine starts and runs but on tickover it is rough and occasionally stalls,

when timing the engine I found I could install only the camshaft locking pin or the crankshaft pin and to me it seemed like the camshaft was set by whoever changed the belt last 1 tooth out from the locking pin hole

I locked the crankshaft with the pin and flywheel plate and painted tell tales on the camshaft & crankshaft pulleys with corresponding marks on the old belt which copied over to the new belt which is how I then proceeded to change the pump/pulleys and timing belt

it now fires up but tickover seems lumpy and occasionally stalls (not good with a auto box) which to me indicates the timing is slightly out

I have checked with my OBD code reader and no faults are showing up

if the timing is out by 1 tooth is does the camshaft pulley have a keyway or is it purely interference fit? as if it is interference fit theoretically I could time the crankshaft and then loosen the camshaft pulley to adjust the pulley to the timing locking pin point and then retighten the pulley bolt

has anyone else had this before if so how did they solve it?

TIA
martin

Both timing pins MUST be in place or the timing will be out.
The crank belt sprocket has an elongated key slot, which allows the timing to be set spot on every time the belt is changed, but in order for the belt to be timed correctly, those pins must be in place before the bottom pulley bolt is torqued to spec.

Now if it has been run for a long time with incorrect timing, then it's possible that the ECM adaptives have tweaked the timing to suit, which if subsequently corrected, could well cause all sorts of issues.

However before messing with adaptive values, you need to make sure that the belt is lined up so both pins are able to engage with the holes easily, which guarantees correct timing.