After a few ideas on this one if possible please, a trader brought me this car a few weeks ago because the MIL light was on due to the above DTC. The car appeared to be running fine except for the hint of a rattle (we all know what that is). I whipped the plugs out, which appeared fine, and did a compression test, all good! I put the no3 coil pack into no2 cylinder and went for a spin; can ran fine and light didn't return so I gave the car back to the customer and explained all.

Since then, the customer has sold the car and sods law the light has come on, the owner took it to VW who diagnosed a faulty timing chain due to the rattle and quoted a fantastic price, the owner then returned to my customer screaming blue murder and after some discussion they agreed to let US change the chain due to obvious cost differences.

The light was on when it came in but no running issues, cleared P0303 and replaced the chain and tensioners etc using proper timing kit. Fired up sweet so I took it for a test drive; after about 1 mile it seemed to hesitate for a second and then MIL came on, no further running issues, at 2 mile marker it lost all power and I nearly got myself killed trying to limp it off a roundabout. It continued to run like a dog in the workshop, not being sure if it was something we'd done I turned it off and read for codes, P0303, cleared it and started it up, runs sweet as a nut again!!!!

It was 5:15pm at this point so I had a look through the live data and everything looked spot-on so I rang the customer and he said he would just leave it with us to sort out, he also noted that he had never had and running issues nor had the new owner reported any, just the light.

Bit stuck for ideas really as it is very intermittent, I suspect something electrical due to DTC clear temporarily solving the issue, also I feel its fuel related due to having already tested the compression and swapping coils round but obviously theres not much I can do without the fault being present. I'm hoping somebody has had this issue before and can point me in the right direction??

Thanks
Craig