Rough idle on hot start

My 320CDI IL6 has developed a problem when the engine is hot and restarted after stopping for a few minutes. The engine shakes like a misfire, but after driving off and getting up to speed, it is okay and will idle fine. It seems worse when the outside temp is 30°+. It shows no faults and has had the mountings replace a year ago. I also get the common knocking noise at 1500 - 2000 revs when hot. I noticed the hot starting problem after filling up with supermarket fuel. Could this be the culprit? Where possible I use Total Excillium, which the car seems to like. Are there any other tests I can do to pinpoint the problem?

 

What year is the car?

 

2000

 

Maybe an issue with the CPS (Crank position sensor) but it needs hooked up to a Star diagnostic first I guess to eliminate the obvious stuff

 

Star shows no problems, but the idle was okay when it was plugged in. It only does it just after a hot start and then it is okay until it is switched off and restarted before it has cooled down. CPS was replaced a year ago as it was faulty.

 

Nothing to do with the CPS.

Sounds like a fuel issue, possibly injector nozzles or quantity control valve..

 

Star shows a fault. P0100-016 B 2/5 (hot film mas air flow sensor) plausibility 1. Air flow low at lower range of speed. Does this suggest that I need a new sensor?

 

I have just changed no 6 injector for a reconditioned one from a German supplier. Car back to normal. No tapping noise and fuel economy back to normal.