3.9 EFI missfire

[hirot]

Hi, I am new to this forum and if all goes well, I will become an avid reader.

I was about to purchase a 1991 Range Rover 3.9 EFI engine to fit into an MGB. The vehicle had stood for about 12 months, outside, but with a new battery started first time. It ran for a few minutes then stopped, but sounded fine. It was re-started a couple of times and the same happened. It now seems to have a missfire and a rattling noise from the centre of the V.

Could this just be a sticking valve, as the vehicle had been standing, or is it likely to be more sinister. The owner has checked plugs, leads etc. and is starting to think it is tappet related.  

I am quite keen on the engine as it had a good history, done around 120,000 miles, was coming out complete with all EFI bits and is a good price.

I am hoping to visit the owner with a hope of identifying the problem by gaining more information.

Any ideas would be very gratefully received.

Regards Ian