Super S slight misfire

[imp124]

Hi

Just a little thing thats been annoying me for a while. When i start her up she runs on 3 cylinders a little on idle (not so the engine is jumping about all over) and smells of petrol outsode the car really bad. But when i get going about 1 mile away its fine and the petrol smell goes away and idles fine.

Dont know what this is at the moment as i have changed:

Spark plugs

Head gasket was done not long ago and it does NOT drink coolant or put oil into water.

Tappets set correct when i did the head gasket and again recently

Dizzy Cap

HT leads

One thing i have not changed is the rotor arm would this be worth doing?

so basically it only does it when te engine is cold, also it doesnt cut out which is good

 

[Shaun]

this sounds like what im going through but my dad said well check over the carb etc just incase the 17years of abuse had finally caught up with it

 

[imp124]

it shouldnt be mine doesnt burn oil / coolant etc and didnt look bad when the head was off

 

[MLC2]

Does it sound like a misfire on one cylinder only?
If so it might be worth doing a compression test to see if one cylinder is low.

 

[superls]

mine does this, but mine is one of the ht leads tracking across to the head, keep forgetting to sort it.

 

[imp124]

Does it sound like a misfire on one cylinder only?
If so it might be worth doing a compression test to see if one cylinder is low.

it does sem like only one cylinder but will check with compression tester soon

 

[imp124]

ok so i have now done a compression test on all the cylinders, i measured and recorded my results and its quite puzzling:

cyl 1 = 130 PSI
cyl 2 = 127 PSI
cyl 3 = 134 PSI
cyl 4 = 130 PSI

The haynes bible says for the MA10 only! but this is what i was going off:

Compression pressure (standard) : 192 lbf/in2
Minimum: 164 lbf/in2
Max difference between cylinders: 14 lbf/in2

so if this is correct also for the MA12 then i have a problem as all cylinders are low on compression, i only left it turning over for approx 6 seconds to build up pressure and for the engine to misfire i was expecting to see a large drop on 1 or 2 cylinders?

any help / advice guys and girls?

 

[frank]

that 192 psi is probably the 5 speed 1.0 spec steve, and 130 psi is,nt bad for an old engine, are you sure the engine is,nt just "hunting" because the choke is on while cold ?

 

[imp124]

i thought that too Frank the choke is off although it does run better but not right when warmed up, it idles very slightly lumpy and sounds a little like a V8 when under throttle, im off to try a rotor arm, have have also changed the carb so its not that, also checked the vac lines

 

[frank]

your vac pipes will only affect closed/low throttle steve, are your plugs a good colour, and equal in colour ?

 

[imp124]

yep all the plugs are are a good colour and replaced recently

 

[hannibal]

that compression looks ok mate....nice and even....but i think frank has a point cos my k10 sounds like a v8 every morning untill its warmed up. I had it crypton tuned about 5 weeks ago and everything was fine but it still runs lumpy when cold.

 

[imp124]

it still sounds like a v8 when warm too nice sound but does my nut in when its not how its supposed to be when warm, oh and a slightly scary experience, tried turning the engine off from a journey round town and it took about 10 seconds from me taking the ignition keys out for the engine to stop! scary...

 

[hannibal]

its running on (dieseling) eather your ignition timing is to far advanced or it needs a decoke or its running verry rich (unlikley as you said the plugs look ok) have a look at your vacuum advance on the distributor,,,make sure is not stuck if its ok check your timing and mixture.also the k10 has a anti run on valve on the carb...make sure this is working (but it wouldnt cause your misfire)

 

[imp124]

i just took the carb off and converted to Weber to check if it was the carb and its not, there is not a vaccum advance on the distrubutor as its all electronic ignition, i think im going to try another set of new plugs, timing check and rotor arm

 

[Shaun]

sorry to bring this up again but did you get this sorted? as its bugging me in the mornings now...

 

[imp124]

Not yet, although my car is not on the road at the moment as im having some work done, i am going to try some carb cleaner etc as i ahve replaced all the ignition system and it does seem to be fuel linked

Steve

 

[Shaun]

okies well if you find out what it is could you kindly let us know thankyou!

 

[Nismok10]

if you go to the new testament of the bible it tells you the 1.2 and yea your running low.. considdering you heads been skimmed.

standard 181lfb/in2 and minimum 172..

 

[Nismok10]

might test mine at some point . when its all done

 

[imp124]

might test mine at some point . when its all done

its low but the main point i was testing is that all the cylinders are consistant, this shows that its wear not broken rings etc which may leave one bore with little compression, i think that would be more likely to cause the misfire imo