15 replies to this topic

[tb205gti]

The mini is acting up, and I need help to find out what is going on..

 

Occasionally it will only run on 3 cylinders. It has done this before, and the last two times i replaced the sparkplug on the misfiring cylinder - and that solved the issue.

 

But lately it has started again, but this time round the spark does come back after some time. It starts firing a few times, then more often and finally it runs perfectly again.

 

Points have been checked, cap as been inspected and cleaned, wires seems good and sparkplug is ok. When it is misfiring I cannot force it to fire again by messing about with the wiring. (if it as a poor connection).

Removing the cap, cleaning the points, etc. does absolutely nothing. It only starts working again when the car decides it is time to start working again. :/ 

 

Once it is working, it never cuts out - it only happens if the car is turned off and left alone for some time. I have _never_ experienced that it would start to misfire when driving.

 

Any thoughts on what it can be?

 

[Carlos W]

Is it always the same cylinder?

 

What colour are the plugs?

[dyshipfakta]

Valve clearance properly adjusted?

[Dusky]

I WOnder, did you try a new spark plug again too?

[Cooperman]

Maybe try a new set of ignition leads, a new set of plugs, check the cap for a small crack, clean & re-set the points and adjust all the valve clearances. That is for a start. If doing all that doesn't sort it come back on here.

[tiger99]

There are only so many things that it can be and Cooperman has the likely ones all well covered. I would agree with changing the leads, cap and plugs. Get the cap from the Distributor Doctor, not a Mini specialist, and while you are there a proper rotor arm and points, if used, may be a good idea.

The other possibility is an intermittently sticking valve. It is somewhat less likely but not entirely unknown.

Assuming you have a single or twin carburettor, we can rule out fuelling, as more than one cylinder would be affected.

If you have a mapped ignition system with cam and crank sensors there are other possible problems.

[tb205gti]

I'll try to answer all your questions.

 

It is the two outmost cylinders that are acting up. Cyl#1 and cyl#4. It is not valves, if I remove the sparkplug and place it on the head and crank the engine - I do not get a spark.

 

The color on the working plugs is good, brown'ish black - a bit too the rich side. :) The one that is not firing is soaked :)

 

A new sparkplug will probably solve it, it has done that before. Running NGK BP8ES by the way.

 

I have checked the cap - seems fine, points have been checked - seems fine. (Issues with the points would affect all cylinders right?)

 

I have new leads laying around, but I need a new cap as the old leads does not remove from the cap. I'll try a new cap and the new leads..

 

Keep you posted.

[tiger99]

"Seems fine" is the problem. You can't really check a cap or leads except for very obvious faults. As I said, change them for new ones from a reputable source, as recommended. They have a finite life expectancy anyway and the new red ones even look better.

Oh, and check your distributor for sideways play in the shaft, ie wiggle the rotor arm, because a badly worn shaft can allow the points to operate normally on some cylinders but not others. It is not very likely, but I have had it happen once on a Lucas distributor on a different car. The check costs nothing so us worth doing.

[Cooperman]

Run the engine in complete darkness, open the bonnet and see if you can see any sparks around the cap and leads.

[tb205gti]

Run the engine in complete darkness, open the bonnet and see if you can see any sparks around the cap and leads.

 

Excellent idea - why did I not think of that :)

[Dusky]

Ngk bp8's Are way too cold unless its a Super Out and Out race engine.

[absx2]

Ngk bp8's Are way too cold unless its a Super Out and Out race engine.

 

I`m with Dusky on this one.

Try BP6ES / BPR6ES as this could be the route of a plug fouling problem due to the cold plugs and over rich mixture.

[tb205gti]

 

Ngk bp8's Are way too cold unless its a Super Out and Out race engine.

 

I`m with Dusky on this one.

Try BP6ES / BPR6ES as this could be the route of a plug fouling problem due to the cold plugs and over rich mixture.

 

 

998 pocketed, 12G940 head, 2xHS2, Cooper Freeflow + RC40 - so not exactly a race engine. :)

 

BP8's should not be too cold, but you may be onto something.. I'll start by cleaning the plugs - if that helps, then they must be too cold for my current setup.

[Dusky]

 

Ngk bp8's Are way too cold unless its a Super Out and Out race engine.

 
I`m with Dusky on this one.
Try BP6ES / BPR6ES as this could be the route of a plug fouling problem due to the cold plugs and over rich mixture.
 
 
998 pocketed, 12G940 head, 2xHS2, Cooper Freeflow + RC40 - so not exactly a race engine. :)
 
BP8's should not be too cold, but you may be onto something.. I'll start by cleaning the plugs - if that helps, then they must be too cold for my current setup.

Way too cold for that spec. Original plugs were 5's I urge you to try bp6 plugs.
I only use 8's in a 140 bhp race engine, on my pwn clubman I use 7's( engine has 115 bhp at the wheels).

[Cooperman]

I use BP6ES in my 1310 cc rally 'S' with 286, 11.1 CR, etc., and it runs well.