Missfire under load

[Turbo97]

Hi there,

I’m having a bit of trouble with a misfiring mini. I bought a 92’ 998cc Mayfair (carb) not too long ago and it has recently developed a missfire under load between 2500 and 3500rpm, it’s also very reluctant to rise above 4000rpm. Idles and revs well in neutral, 1st and 2nd gear, but 3rd and 4th are proving problematic with a significant missfire when you put your foot on the throttle. Backing off and easing gently into the revs seems to reduce the issue slightly.

I drove the car almost 140 motorway miles back home after collection with no issues and since have done only minor service type bits and pieces (timing, compression testing and spark plugs).

After doing some digging around online, owners with similar issues have pointed towards the coil and distributor (she’s on points at the moment) and timing as the main culprits for this sort of issue.

Has anyone else experienced anything similar or have any other ideas as to what might be causing the missfire?

Cheers in advance🚗

[phumy]

In order of cost effectiveness, cheapest first;

1 Clean up and adjust points.
2 Fit new condenser
3 Fit new coil
4 Fit new ignition leads

Hope that helps.

[STO]

^^^^ This plus distributor cap

[phumy]

Correct, that probably fits between 2 and 3. In fact if they haven't been done or checked for a few years I would be inclined to change the lot and be done with it. It's not too expensive in a Mini anyway.

[Turbo97]

Ok thanks that’s great. I’ll give them all a go and let you know if it works!

[Dinlowgoon]

Is there oil in the carb dashpot ?

[Lesgrandepotato]

Change one thing at a time! If not you’ll be rueing it when it won’t start again.

[rufusruffcutt]

One other thing to think about apart from what was suggested above, does the car have a vacuum advance on it? if faulty these can cause odd behaviour like the OP mentions.

[Drooles]

Yep, check vacuum advance...

Also, echo the oil in the dash pot comment. These are the very easy fixes.

Then it’s plugs, leads, points, condenser, carb set up etc.

Hope you get it sorted