Intermittent Misfire

[jamie_1992 66 1 Cars]

my 1.4 xs has a misfire that only occurs at low revs, so either when sat idling for a minute or so or driving under load at low revs eg when putting you foot down in high gear at low speed

 

i have changed the plugs, leads, rotor arm and dizzy cap

i have also cleaned the carb but squirting some carb cleaner in it (not sure if its done anything)

 

the plugs seem to be sooting up (going black rather than the gray they are ment to be)

i have cleaned them up but still seems to be the same

 

im running out of things i can think of

any ideas anyone???????

[Liquid_106 97 1 Cars]

Aren't blackened plugs a sign of over-fuelling, either that or a weak spark so the available fuel isn't burnt completely?

[jamie_1992 66 1 Cars]

that is what i thought but im not sure how you adjust the mixture on it

[Lan 24 1 Cars]

mixture screw is at back left hand side of the carb (when your facing the front of the car) recessed in a hole, a small flat blade gets to it, anti-clockwise for leaning of mixture and vice-versa.

 

have you got a good strong spark first though?

[jamie_1992 66 1 Cars]

is there a way of telling if you have a strong spark?

[Lan 24 1 Cars]

pull the plug out have it touching a some metal to earth it, get someone to crank the engine while you watch for a spark if it is only weak or non-existent you will need a new coil, you can also get plug inline spark testers for a few quid.

[jamie_1992 66 1 Cars]

thanks il give it a test tomorrow