Hey guys, got a problem which has me puzzled....

This last 2 weeks my datto ute has developed an inconsistent knock/misfire at very low rpm (roughly 500-800), if I move the idle up to 900+ the knocking goes away as does the missing, acceleration and deceleration is fine as far as I can tell, the knocking seems to cause the misfire as they happen at the exact same time or perhaps its the misfire causing the knocking, but ive checked the spark plugs, dizzy cap needed a clean up, next im planning on changing the coil and leads but im hoping someone here may have an answer to my problem.......im praying its nothing mechanically wrong.......

Engine/Drivetrain specs below.

A14 engine with a A12 head, 60 series 4 speed, extractors, 32/36 weber, electronic dizzy, electric fuel pump, some mild engine and head work......

Hmmm from past experience an intermittent knock has always been bearings for me especially if it comes and goes respective to revs. But the misfire is interesting. Is your timing okay? Its not preignition is it?

Best practice is to confirm your ignition timing and valve timing and see if the symptoms persist. Good luck, hope its not serious.

I have checked all the valve clearances, they are spot on, still have not checked the timing though.

http://youtu.be/9hTX8ecEubY

Hope this video helps.

Shouldn't the idle speed be 800 or 850 anyway? Could be the idle mix isn't quite right. There's separate adjustment for that. Also, check your idle oil pressure, could be a little low which might mean the oil pump's a bit worn.

Are you suggesting that the knocking could be a result of low oil pressure?

My oil pressure sits at about 40psi at low idle and rises to about 70-75psi at a 100kmh cruise speed, not sure if that's what its meant to sit at.

That oil pressure sounds pretty good. I'm not sure of the specs either but it's higher than a fresh old holden engine sits. Is it possible the knock is something rattling when it's idling rough?