I had one of those days. Did the tune-up on the t/c engine yesterday and it was running pretty good. few carby/ fuel pump tinkering but it was idleing a little rich.
Finished last night [or early this morning] and went back to-day to fit the air cleaners back on, fire it up and set the idle mixture. Started the engine and it ran like a bucket of sh*t on 3 cylinders at idle. reved it and it ripped up to 6000 instantly. Back to idle and ran on 3 cylinders
OK did all the obvious checks plugs, leads, carby mixture etc,etc,etc. No good. This had me scratching my head. the carbys all over-hauled and I could not find what was wrong.
Called in my resident motor bike carby expert and after a few beers and checking he could not figure it out.
So I spat the dummy and pulled the carbys off and stripped down the offending unit. Removed the emulsion tube air feed and found the problem.
A stinking little tiny fu********************************ing flying insect had been sucked into the air supply port in the front of the carby and blocked the emulsion tube.
A whole day wasted

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Research is the difference between speculation and investment. Anyone who copys some one else will always be second
www.minisprintgt.com

Yeap, that's all it will take....................

I recon mixing a bit of Baygon to the fuel would fix those sort of problems. That was a big piss off.

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DID I MENTION THAT I AM THE BEST SUPPLIER FOR MINI ELECTRICAL PARTS AND REPAIRS?
"Let us remove your "SHORTS"

I'm having the same issue on my Rover at the moment.

Fine when you put your foot down, drives fine under power.

Let it idle and it runs on 3, coast along the road with no load on engine and runs on 3.

David, it's good to see you're sorting out all the bugs

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Too many cars, and too little time.

Maxi23, I guarantee it will be one of the Pain in The A55, vaccuum hoses under neath the EFI, check them all or its best to replace them all, it won't hurt but should fix the problem, definately sounds like a vaccuum problem....

Any better ideas will be considered.

Cheers............

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A good fuel saving feature when your not heavy under acceleration

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1965 Morris Mini Deluxe - 998cc SC12

(Totally at Davids expence of course! )

I remember reading a similar story in an old car mag, except it was a spider web in the engine of a Rolls Royce that had undergone a complete resto. Cheeky bugger had made himself at home for several months while they reassembled the vehicle, they wondered why the overhauled engine simply wouldn't run!

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I had a leyland P76 v8 that started to idle with a miss it would run fine as soon as you accelerated as i had twin exhaust that were seperate from each bank of 4 cylinders i could tell aleast the side of the motor that had the miss at idle.I tried everything like spark plugs and cables etc after one hole day of frustration and wasted time i decided i would take of the cylinder head off and have a looky inside as i had run out of ideas as it turns out i only got as far as pulling the inlet manifold of and there was a tiny little split in the inlet manifold gasket i thought you barsted thing over the years it must have shrunk and split.So put new gasket on fired the motor up and all was good .So guess there was just enough air leeking through the gasket at high vacuum at idle to lean out that one cylinder making it misfire

I had a 1926 Chev 4 paddock basher (yep, showing my age here), it went like a train until hot (normal temp) then would stop. No go until it cooled down a lot.
It had me stumped for a couple of weekends, then one day for some reason? I decided to adjust the rockers.
The exhausts were down to a couple of thou clearance- as it warmed up the valves got longer, and they all stayed off the seats until cooled.

Set them all, SAE50 oiled the felt on top (no pressure lube to rockers on Chevs back then) and bob was my uncle.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Interseting Doc, you may have just answered something that has puzzled me for the past 26 years. I had a '55 Chev back in 81-83 that used to do the same thing. Drive it for an hour and it would stop. Let it cool down and off it would go again. Mechanics at the time just scratched their heads