Mini Engine Running on

Post by **AndrewSkinner** » Mon Apr 16, 2007 9:01 am

Sorry if there is an original post but I cannot find it.

I have a problem with a friends Mini. After the mini has been switched off the car engine (Normaly when hot) runs on for few seconds. The time it runs on for can vary from a few revolutions to running on for a good few seconds??

What could this be?

Post by **Myko2** » Mon Apr 16, 2007 9:28 am

I have the same problem with both my coopers. I just put it in 2nd gear and gently ease off the clutch as I shut them off. I am sure it is a timing thing, but they seem to run best at the setting they are at now.

Post by **Stig** » Mon Apr 16, 2007 10:01 am

It's a common problem with high(ish) compression engines - so not that common with Minors then.

Basically the engine is running like a diesel, the fuel mixture is still going in and getting compressed but is self-igniting due to the compression and heat rather than a spark after you've turned the ignition off. It's aggravated by carbon deposits on and around the valves as these will be glowing nicely so a decoke can cure it. The running-on isn't doing the engine any real harm, though it can be annoying, but may indicate that the engine's running too hot (lean mixture, over-advanced timing etc.) or it may just be a high compression engine. What do the plugs look like?
My Metro used to do the same thing (needed a decoke) so I used to lift the clutch a bit as I switched off too.

Post by **bmcecosse** » Mon Apr 16, 2007 10:42 am

Yes - it's being ignited by a glowing piece of carbon. There is a Redex treatment that can be used - be aware it creates clouds of smoke and should be done well out in the countryside, and some say if you dribble small amount of water thorough the engine when it's hot and running at a fast idle this has the same effect. Otherwise - clean the spark plugs and perhaps just try a different brand of petrol. The ignition timing is likely to be running retarded rather than advanced to give this problem, so you could try advancing it slightly until it's 'pinking' - and then back off until it's just not quite pinking!

Post by **Dominic** » Mon Apr 16, 2007 8:33 pm

I used to have that same running on problem on a 1965 MGB roadster, that had been bored out to 2 litres. The only way to stop it quickly was to brake it with the clutch! Not very satisfactory! I was told at the time by a local sports car specialist that an anti run-on valve could be fitted? No idea where or how!
Talking of Minis, my partner's daughter has a 1990 Mini, 998cc. How often should the oil be changed? every 3000 or every 6000? She has done 3000 since buying it just before Xmas. Also, should she be using good old 20/50?
Thanks folks.

Post by **bmcecosse** » Mon Apr 16, 2007 10:31 pm

Change it as often as you can! Especially if it does lots of short runs. Most Minis dribble the oil out on the road - and so get a constant feed of new oil on a wekly basis. And yes - 20W50 it is - the Asda/Morrison stuff is fine.
Anti run-on valve just lets a slug of air into the manifold and so quenches the fire. Metros had them fitted to their A series engines - so if you really want one that may be a source! I find with a light fliywheel the engine stops dead when switched off.

Post by **Dominic** » Mon Apr 16, 2007 11:08 pm

Most Minis dribble the oil out on the road - and so get a constant feed of new oil on a wekly basis.

She's a lucky girl, her Mini has only done 30,000 in total, so engine is still oil-tight, hasn't used more than a cupful since she bought it. Looks like I'll have to share my supply of oil & filters then!

Post by **bmcecosse** » Mon Apr 16, 2007 11:10 pm

Hmmm - must be a record low oil consumption for a Mini. Write to Guinness Book of Records!

Post by **Dominic** » Mon Apr 16, 2007 11:15 pm

hmmm is the prize a pint of guiness?

Post by **Packedup** » Tue Apr 17, 2007 1:11 am

Dominic wrote:She's a lucky girl, her Mini has only done 30,000 in total, so engine is still oil-tight, hasn't used more than a cupful since she bought it. Looks like I'll have to share my supply of oil & filters then!

It's not the engine that leaks, it's the seal round the gear change rod. If there's not even a trace of oil around there, I'd be worried there wasn't any in the engine at all!

Post by **Myko2** » Tue Apr 17, 2007 6:56 am

I change the oil in the minis as soon as it starts to show a bit of color. Since they don't travel very far anyway. I'd say that's around 1K to 1.5K mi. or about every 6 months. I use 20/50 castrol. It's cheap insurance.

Post by **minor_hickup** » Tue Apr 17, 2007 5:05 pm

The only way I cured the running on in my minor was by de-coking the head, tried everything else and must have put gallons of redex through it.

Post by **bmcecosse** » Tue Apr 17, 2007 9:28 pm

Water injection does work - if you have ever taken the head off an engine where a little bit of water has been leaking into one chamber (via head gasket) then that chamber will be spotlessly clean - no carbon at all.

Post by **minor_hickup** » Tue Apr 17, 2007 10:51 pm

Admittedly I didn't try the water injection, just because I didn't like the idea of it. Mind you I took the head off because I had a broken exhaust valve, not to cure the running on, that was a pleasant side effect.

Post by **bmcecosse** » Wed Apr 18, 2007 7:41 am

Broken valve trumps running on easily!