petermcpete Posted December 24, 2018 Share Posted December 24, 2018 I've taken the Toledo 150 miles south for Christmas, but am now faced with a bit of an issue. As a present, the Toledo has given me 3 plugs firing, 1 plug not. The engine (1296cc Spitfire MK4) has started misfiring at idle. It's only the one plug, and it seems to start firing at higher revs - I've had the spark plug light tester thing on it.I've tried a few different plugs, a different HT lead and a different rotor and dizzy cap - but still exactly the same on that cylinder! Any ideas?It's still drivable - I just have to not let the revs drop at junctions - but it's certainly not ideal! Link to comment Share on other sites More sharing options...
Rocket88 Posted December 24, 2018 Share Posted December 24, 2018 I've taken the Toledo 150 miles south for Christmas, but am now faced with a bit of an issue. As a present, the Toledo has given me 3 plugs firing, 1 plug not. The engine (1296cc Spitfire MK4) has started misfiring at idle. It's only the one plug, and it seems to start firing at higher revs - I've had the spark plug light tester thing on it.I've tried a few different plugs, a different HT lead and a different rotor and dizzy cap - but still exactly the same on that cylinder! Any ideas?It's still drivable - I just have to not let the revs drop at junctions - but it's certainly not ideal! Try swapping the plug with one of the others........ petermcpete 1 Link to comment Share on other sites More sharing options...
Squirrel2 Posted December 24, 2018 Share Posted December 24, 2018 Is there any play in the distributor shaft? I.e. is it floating around and upsetting the points gap at idle? Squirrel2 Link to comment Share on other sites More sharing options...
petermcpete Posted December 24, 2018 Author Share Posted December 24, 2018 Try swapping the plug with one of the others........Yep, done that, swapped with a plug from another cylinder - no luck. Link to comment Share on other sites More sharing options...
somewhatfoolish Posted December 24, 2018 Share Posted December 24, 2018 Valve clearance closed up and not sealing? Is the head unleadified? Link to comment Share on other sites More sharing options...
petermcpete Posted December 24, 2018 Author Share Posted December 24, 2018 Is there any play in the distributor shaft? I.e. is it floating around and upsetting the points gap at idle? Squirrel2Seems alright - the rotor doesn't wobble if that's what you mean? Link to comment Share on other sites More sharing options...
petermcpete Posted December 24, 2018 Author Share Posted December 24, 2018 Valve clearance closed up and not sealing? Is the head unleadified?I'm using lead additive, but I don't think it's this, I think it's electrical - there's clearly no spark at idle, but there is at higher revs... Link to comment Share on other sites More sharing options...
N Dentressangle Posted December 24, 2018 Share Posted December 24, 2018 I'd also suspect valves: you've changed all of the ignition system components to that plug, and you still have the same consistent problem. Not hard on that engine to whip the rocker cover off and see what the clearances are on that cylinder. However, if that plug is actually not sparking at idle then you've not found the ignition component causing the problem. I would go through changing the components one at a time again, methodically, and also try a different condenser if you have one. Is the distributor body tightly clamped, ie can it be turned? Could the timing have slipped in that way? petermcpete 1 Link to comment Share on other sites More sharing options...
Guest Hooli Posted December 24, 2018 Share Posted December 24, 2018 Give the engine to Captain70s & he'll diagnose it in the months to come. More seriously, valves sound a good shout to me too. Link to comment Share on other sites More sharing options...
Squirrel2 Posted December 24, 2018 Share Posted December 24, 2018 Seems alright - the rotor doesn't wobble if that's what you mean?Yes, I was thinking that there was something that was causing the distributor cam/points follower heel to ‘wobble’ at the same spot on each rotation. With the engine running can you get the lead to the non-firing plug to spark? This would eliminate the ignition as being the source of the trouble. Squirrel2 petermcpete 1 Link to comment Share on other sites More sharing options...
petermcpete Posted December 24, 2018 Author Share Posted December 24, 2018 VID_20181224_171238.mp4Occasionally firing at idle. VID_20181224_171259.mp4Fires when given a bit of revs. Link to comment Share on other sites More sharing options...
petermcpete Posted December 24, 2018 Author Share Posted December 24, 2018 Yes, I was thinking that there was something that was causing the distributor cam/points follower heel to ‘wobble’ at the same spot on each rotation.With the engine running can you get the lead to the non-firing plug to spark? This would eliminate the ignition as being the source of the trouble.Squirrel2Yep - when the lead is swapped to a different plug, it fires every time. Just doesn't seem to like this plug/cylinder combo. Link to comment Share on other sites More sharing options...
petermcpete Posted December 24, 2018 Author Share Posted December 24, 2018 VID_20181224_170853.mp4Whoops - wrong one before - this is the engine at idle (occasionally fires). Link to comment Share on other sites More sharing options...
N Dentressangle Posted December 24, 2018 Share Posted December 24, 2018 OK. I'd still do the things I suggested in my previous post. What's the battery like? Is the engine earth lead in good condition? Is the battery earth lead good? petermcpete 1 Link to comment Share on other sites More sharing options...
purplebargeken Posted December 24, 2018 Share Posted December 24, 2018 At least it is a piece of pee to check stuff generally. Link to comment Share on other sites More sharing options...
Rocket88 Posted December 24, 2018 Share Posted December 24, 2018 Could be plug oiling up.....any sign of blue smoke? Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
Asimo Posted December 24, 2018 Share Posted December 24, 2018 The distributor cap? Each cylinder uses a different section of the cap - is the stud for that cylinder damaged? If the points gap has closed up it MAY be that tolerances between the 4 cam lobes allow 3 sparks but not the fourth and just at low speeds? Me? I'd check the valve clearances next. BeEP 1 Link to comment Share on other sites More sharing options...
bigstraight6 Posted December 25, 2018 Share Posted December 25, 2018 I’ve had similar issues with my old chod caused by shit quality distributor caps where the contacts inside rapidly wear and the minute metal particles off these make misfiring and running problems, the last time it happened was with the Triumph 2000 and the car was hardly driveable, a new cap sorted it... Link to comment Share on other sites More sharing options...
mercrocker Posted December 25, 2018 Share Posted December 25, 2018 I've only just come into this thread but my money would be on dizzy cap too. My mechanical knowledge is only average but my experience long and bitter..... bigstraight6 and tooSavvy 2 Link to comment Share on other sites More sharing options...
petermcpete Posted December 25, 2018 Author Share Posted December 25, 2018 I'd also suspect valves: you've changed all of the ignition system components to that plug, and you still have the same consistent problem. Not hard on that engine to whip the rocker cover off and see what the clearances are on that cylinder. However, if that plug is actually not sparking at idle then you've not found the ignition component causing the problem. I would go through changing the components one at a time again, methodically, and also try a different condenser if you have one. Is the distributor body tightly clamped, ie can it be turned? Could the timing have slipped in that way?OK. I'd still do the things I suggested in my previous post. What's the battery like? Is the engine earth lead in good condition? Is the battery earth lead good?The distributor cap? Each cylinder uses a different section of the cap - is the stud for that cylinder damaged? If the points gap has closed up it MAY be that tolerances between the 4 cam lobes allow 3 sparks but not the fourth and just at low speeds? Me? I'd check the valve clearances next.Thanks all, I've checked the valve clearances and they all seem good. It's got an electronic ignition, so no points gap to be checked. I've tried a couple of spare dizzy caps, same end result. All engine earth cables are good. My thinking is it must be the grounding of the spark plug (based on the video below attached), as it fires when grounded elsewhere - but what can I do apart from clean the thread (which I've already done), try a different spark plug, check connection between HT lead and plug is good, check plug gap...? Confusion... UPDATE: having written this out and waiting for a file to upload, I cleaned the plug holes again and cleaned the end connections on the leads...now it's all good! Took for a test drive and it quickly relapsed, but another clean and all good again...think I'll be replacing those leads (again)...Thanks all and merry Christmas! Asimo, N Dentressangle, purplebargeken and 1 other 4 Link to comment Share on other sites More sharing options...
Ghosty Posted December 26, 2018 Share Posted December 26, 2018 Give the engine to Captain70s & he'll kill it altogether in the months to come. FTFY Link to comment Share on other sites More sharing options...
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