After a good run on the weekend, the mini has developed a mystery miss again.

It sounds &feels like it is running on 3 cylinders when idling (Rough and irregular engine sound) and when not under load. Put your foot down and the miss goes, and all the power is there.

What should I be looking at that may cause this ?

Would an earth strap with a fairly frayed engine block end have any effect ?

The only thing I can think of it being on you car would be plugs or leads.
The injection should take care of everything else, that is if theres a problem it (inj), it would be all wrong or nothing.

I'd be looking for a vac leak.

It will miss at idle, then on open throttle theres no vac therefore no vac leak and all will run well.

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Dean Hutton's first car was a Mini.

Both the above are what id be looking for before going any deeper

check that the inlet manifold is actually tight

edit--> as in that it`s mounted properly---> all nuts/bolts are done up tight

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No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.

I could remember something similar being posted before , not sure if it's the same issue but worth checking anyway ,

http://www.ausmini.com/forums/viewtopic ... ected+hose

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Have a look through the section relating to SPI/MPI on TMF.
Has helped me with a few problems, there is a lot of good reading on there so make a cuppa have a read.
Cheers Pete
http://www.theminiforum.co.uk/forums/in ... wforum=140

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A recent study found the average Aussie walks about 900 miles a year
Another study found Aussies drink, on average, 22 gallons of alcohol a year
That means, on average, Australians get about 41 miles per gallon

Kind of makes you proud to be an AUSSIE

Thanks for the advice people!

I will pick up some new plugs this arvo, as I swapped back to an old set of leads and still had the same problem.

I will also pull off the hoses from the manifold/ecu also and give them a check over.

Now onto the uk mini forum for some 'light' reading

Thanks!

Turns out ALL the bolts holding the exhaust and inlet manifolds on the head were not done up.

I was able to do them up tighter with my fingers before I even touched them with the spanner.

Did the water mist trick after advice from local Mini workshop guy.