Misfire, Rough idle, Running on 3 cylinders

[domruffle1984]

Hello,
i'm hoping to get some advice on a problem i have with my van it is a 2.0l Aircooled 1983 with twin solex carbs, i recently had the ignition coil replaced and whilst in the garage the timing was adjusted. a couple of weeks later i noticed on starting the van it had a very rough idle and the engine rocking as tho it was going to fall out! only keeping the revs
high would prevent it from stalling, then when driving the van if the speed is low and the revs low on acceleration it would shudder very badly, after a few simple test i discoverd that the spark coming from the ht lead then to cylinder 3 would only spark when the revs were held high. when the engine has warmed the idle improves but the running problem does not. I also noticed the new ignition coil gets very hot to touch is this normal?
I have already ordered myself new leads, spark plugs, and a new dizzy cap. I was just wondering if anyone had experienced anything like this or any advice on what else to have a look at.
cheers

[BOXY]

If you've narrowed it down to no.3 not firing. Take out the spark plug and swap it with no.4 and see if the mis-fire moves to no.4. If it does the plug is the culprit.
If there is no change, swap the HT leads over completely between 3 & 4. If the mis-fire move to no.4, then the HT lead is the culprit. If the mis-fire is still on no. 3 you now know your plugs, leads are ok and there might be a small chance the dizzie cap is the culprit. Considering how cheap they are I'd get one and keep it as a spare if it doesn't cure the mis-fire.
If it is only the no.3 that is mis-firing and you've eliminated the ignition side by doing the above, then you need to check your compression to see if you've got a valve problem. Either mis-set or a valve seat issue.

[domruffle1984]

Ok great, thanks for the advice i will carry on with looking at ignition side first and go from there.

[Ian Hulley]

after a few simple test i discoverd that the spark coming from the ht lead then to cylinder 3 would only spark when the revs were held high. when the engine has warmed the idle improves but the running problem does not. I also noticed the new ignition coil gets very hot to touch is this normal?
I have already ordered myself new leads, spark plugs, and a new dizzy cap. I was just wondering if anyone had experienced anything like this or any advice on what else to have a look at.
cheers

If the coil was faulty it would be faulty on all the cylinders, maybe the issue on #3 creates resistance and the coil gets hot. As our friend has said swap the #3 lead for a known good one and if that doesn't work swap the plug ... this is why you should always keep the last set of known good cap, arm, leads and plugs that way you can do a 'system restore'

These things are simple so usually there's a simple explanation ... and remember just cos something's 'new' doesn't mean it's good

Ian

[domruffle1984]

Thank you for your input that is a good point you made about the coil, ive got a some new parts being delivered today so hopefully i can cure the prob.

[domruffle1984]

Well after changing the spark plugs on all cylinders, all HT leads and a new dizzy cap the problem still remains, after about 5 mins of rough idle i felt around each cylinder and all are hot to touch except one which much mean it is still not firing. what would be the next line of enquiry please?

[chrisbeck]

Hi
Check the distributor for wear in the shaft and on the individual small lobes that open the points, also check the valve clearances unless its got hydrolic cam followers.
Another thing to check would be for air leaks on the intake side, if you have already eliminated all of the ignition system

Chris

[California Dreamin]

Time for a 'Compression Check' to see if all 4 cylinders are mechanically fit and producing good readings within 10 - 15% of each other.

Martin

[domruffle1984]

Is there any simple tests i can do to make sure the distributor is working correctly? i also thought i should mention when it was at the garage a couple of months back the timing was adjusted but was unable to be set 100% as the vacum can fouls on the surrounding tinware, if u look down at the unit the can is at roughly 7 o clock, i just saw a post which states if that this is the case the dizzy has been fitted 180% the wrong way round and the can should be at 4 o clock position? any thoughts please?

thank you for all your posts so far.

[kevtherev]

yes you can check the distributor.
pull out No. 3 plug with lead on, hold it on a good earth (engine) and start it up
you should see a good white spark.

have you looked at the engine running in the dark?
this sometimes shows up any tracking of the spark pulse to other places causing a weak and interrmittent spark

[BOXY]

the can is at roughly 7 o clock, i just saw a post which states if that this is the case the dizzy has been fitted 180% the wrong way round and the can should be at 4 o clock position? any thoughts

4 o'clock & 7 o'clock are 90' apart not 180'. If the dizzie had been fitted 180' out the can would be at 10 o'clock. Have a look at the side of the dizzie and see if you can read the part number. Maybe someone has fitted the wrong one?

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[domruffle1984]

Hello all well after eliminating all the simple things i resulted in using an Aircooled specialist garage to solve my prob it turned out the distributor had been in the wrong position which ment the timing could never be set correctly, so after being turned back roughly 90 degrees and timing reset and points adjusted the van has never run so smoothly.