Engine Issue - Sounds terrible, misfiring and a rattle at high revs

[emc]

My 172 Cup at 84k miles, has been running quite rough and misfiring. The car had the belts done at 72k miles, but I now the dephaser has gone also in fact it probably went around 3000miles ago. I drive around 500 miles a week, so the car has been getting a lot of use.

I've got the car booked in with Dan at 519 automotive on Tuesday, but over the weekend the engine seems to have taken a turn for the worse and now sounds like something else has gone wrong. It's down on power by around 10% I'd say compared to 1 month ago. I was hoping I could use it to get to work and back on Monday, but I'm not so sure now. My Dephaser has been dead for some time, but I've been holding back to get some 438 cams fitted when it gets replaced.

This is the engine at low revs and apologies for the dodgie camera work:
http://www.youtube.com/watch?v=vMfmnKTt3nw

This is at high revs and if you listen closely you can hear the rattle at just as I let the revs off:
http://www.youtube.com/watch?v=AqO8MTT2L0g

The rattle tends to happen around 5000rpm especially when letting off power and sounds like a rock rattling in a baked bean can. I though it was the exhaust, but I've had a look around as close as I can and couldn't find any issues. I don't have any jack stands though, so this is a pretty useless inspection.

Any idea what the major issues could be or if it's safe to drive?

At the moment my list of possible issues:
Sparks
HT Leads
Exhaust Mounts
Engine Mounts
Exhaust Gasket
Timing?

 

[Laine_16v]

Sounds quite serious to me, like something in the bottom end has let go Im most probably wrong and i hope i am for your sake!

 

[emc]

My heart went into my throat reading your post. I've been putting the possibility of a serious problem into the back of my mind, but I have to be realistic I guess.

 

[Laine_16v]

Im sure Danny will be here shortly to advise, but you'll be in safes hands with him on Tuesday anyway, hope you get it sorted!

 

[Dan519]

sounds like it's running on 3

 

[emc]

Thanks for looking Dan, bit nervous about using the car if it's running on 3 cylinders after my experience with lovely Corsa engines.

Right, well it might just be mind tricks, but I've had a quick wiggle of the map sensor and it seemed lose. After that it seems to sound much better, but it's definitely still running a bit rough.

edit: No fault codes showing up when I enter the diagnostic mode, but I know that can be useless on occasion.