17 replies to this topic

[minitalia1275]

My 1990 standard Mini 998 was misfiring this morning and only running on three. While running the engine, I removed each HT lead separately to see which cylinder was dead. I found the 4th wasn't making any difference when I removed the lead.(There was a spark) I replaced it with a new lead and it was still the same. I then put in a new spark plug and everything was fine, running on all four.
I then put the faulty plug in another cylinder and it was running perfectly.
I don't understand why the plug was faulty on one cylinder but was running perfectly on another

[mini13]

do a compressin check,

 

also check the val clearances on that cylinder in case the tappets have come undone.

[rww]

   Check all your plug gaps.

 

   Whilst you were running on 3 cylinders , the fourth spark plug was being coated with petrol and the spark tracked to earth. When you put this 'wet' plug in a nice warm and 'dry' cylinder it was able to fire and clear the misfire.

 

Probably nothing seriously wrong but it might indicate you need a service or just new plugs.

[slidehammer]

What you might find is the plug wasn't good enough for a cold start (breaking down) but when put in an already warm cylinder it was producing enough of a spark to keep that cylinder running (which had warmed up a bit from your earlier attempt at starting the car). I suggest it goes in the bin. 

[minitalia1275]

Thanks for advice. I have checked the compression and it is the same in all four cylinders.
Very cold this morning and I most probably gave it too much choke, soaked the faulty plug and ran rough all morning until I replaced the plug.
The plugs were newish, about 500 miles but I will replace all four

[Northernpower]

As a "belt and braces" you may also want to check the distributor cap as well for hairline cracks around the contact where the faulty plug is connected to.

[minitalia1275]

Yes, I have bought a new distributor cap, points and condenser. I will fit them today.
The HT leads are new.
Thanks

[MIGLIACARS]

Ive always found mini love new plugs, and when ive had one foul its for the bin. Not worth the effort of trying to clean it as there so cheap.

[minitalia1275]

Job done! I just took the Mini for a run and all is perfect again. The faulty spark plugs are in the bin.
Thanks for the advice

[rww]

Thanks for advice. I have checked the compression and it is the same in all four cylinders.
Very cold this morning and I most probably gave it too much choke, soaked the faulty plug and ran rough all morning until I replaced the plug.
The plugs were newish, about 500 miles but I will replace all four

 

    It was 'VERY COLD' in Italy ?????? !!!!     

 

 

  Blimey, just looked. It's as cold as here.

Edited by rww, 28 November 2017 - 04:56 PM.

[minitalia1275]

Thanks for advice. I have checked the compression and it is the same in all four cylinders.
Very cold this morning and I most probably gave it too much choke, soaked the faulty plug and ran rough all morning until I replaced the plug.
The plugs were newish, about 500 miles but I will replace all four

 
    It was 'VERY COLD' in Italy ?????? !!!!     
 
 
  Blimey, just looked. It's as cold as here.

Yes, it was freezing this morning. Snow is forecasted for the weekend. We are not too far from the Alps, I already have the snow tyres fitted on the Mini but I never use it in the snow

[phillrulz]

Noticed yesterday after getting my mini back from the sprayer how it was running HORRIFICALLY. Sounded as if it was only running on two... Realy lumps. Got about 100m pulled over and checked leads.... After a few mins of idling and a few yanks of the throttle cable with plenty of choke it cleaned up. But i reaaaly felt like i had a problem... 

[minitalia1275]

Unfortunately the problem hasn't been resolved. New spark plugs fitted but still fouling on one cylinder and running on three. When I fit another dry plug, all is fine.
So far I have fitted new plugs, HT leads distributor cap. Carb and timing spot on. Compression perfect.

[Retroman]

It proves Miglia's point...they do like new plugs !...did you gap them all ?   have you checked the valve clearances ?

New condensor fitted ?

Wondering if its the grade of plug with it being colder air than 'normal'....

 

On Std 998 we use NGK BP5ES, not sure what plugs you run ?

[Northernpower]

Unfortunately the problem hasn't been resolved. New spark plugs fitted but still fouling on one cylinder and running on three. When I fit another dry plug, all is fine.
So far I have fitted new plugs, HT leads distributor cap. Carb and timing spot on. Compression perfect.

Just thinking outside the box, when you say it's wet, are you sure it's wet with petrol. What's your oil consumption, I'm thinking about a leaking valve stem oil seal?