yorkshire_spam Posted August 23, 2022 Share Posted August 23, 2022 On the way back from the 10cr drivers briefing the car developed an issue around Sheffield... Prior to that no problems maintaining 70MPH on the motorway, but then it started to misfire/stutter, at first it was hard to tell and I thought it might just be a sudden headwind gust, but as we went on it got more frequent/severe and seemed to also affect the rev counter. Easing off seemed to mitigate the problem, but by Barnsley we were doing about 55/60MPH so I considered discretion was the better part of valor, so we turned off and came home via the minor roads rather than try to maintain motorway speed. Car ran fine all the way home at lower RPM/Speed It's an 1850 with the original delco dizzy, but a lumenition electronic ignition. Any ideas? Quote Link to comment Share on other sites More sharing options...
Clive Posted August 24, 2022 Share Posted August 24, 2022 Not helpful, but either coil or distributer related. You need to see if it does it from startup, or does it need to get hot? Do you have a spare dizzy? You can pinch the coil off the spit to carry and substitute. Quote Link to comment Share on other sites More sharing options...
yorkshire_spam Posted August 24, 2022 Author Share Posted August 24, 2022 Thanks Clive, my thought was coil starting to over-heat/break down, but only after prolonged high rpm running. It seemed to run fine after I backed off and took to the minor roads (but didn't get chance to really get it as high up the RPM - was more focused on navigating home!) More road tests later today after work. Quote Link to comment Share on other sites More sharing options...
RobPearce Posted August 24, 2022 Share Posted August 24, 2022 You said it "seemed to affect the rev counter" - do you mean the needle flickered with the misfire? If so, it suggests that it's a low-tension ignition problem, so either the dizzy or the Lumenition box. The coil is unlikely to cause this (although it's possible on very early cars with the current-sensing rev counter that's wired in series with the coil, rather than in parallel). Quote Link to comment Share on other sites More sharing options...
yorkshire_spam Posted August 24, 2022 Author Share Posted August 24, 2022 46 minutes ago, RobPearce said: You said it "seemed to affect the rev counter" - do you mean the needle flickered with the misfire? Yes Rob, exactly that - with the very brief stutter/miss I got early on it wasn't really noticeable on the rev counter, but the worst miss it did as I re-tried pushing on the motorway (felt like the engine was cutting out completely - which is what persuaded me to take to the a roads) the counter died and then came back as the engine did. For the "middle" issues it flicked each time it stuttered. The car is an early (pre-3mm pin / pre June 1973) Dolomite - but I can't make sense of the wiring diagram in the WSM as to weather it's a series or parallel rev counter) Quote Link to comment Share on other sites More sharing options...
yorkshire_spam Posted August 24, 2022 Author Share Posted August 24, 2022 A bit of reading around on the Dolomite club forum suggests it's a series tacho and could actually be the cause of the problem if there's a fault with the tacho. Great... another possible cause! Just what I needed! 😉 1 Quote Link to comment Share on other sites More sharing options...
RobPearce Posted August 24, 2022 Share Posted August 24, 2022 32 minutes ago, yorkshire_spam said: Great... another possible cause Quite easy to test for that one, though. If the misfire is repeatable, you can bypass the tacho and it will go away if the tacho is at fault. 1 Quote Link to comment Share on other sites More sharing options...
yorkshire_spam Posted August 24, 2022 Author Share Posted August 24, 2022 Until I do some more testing this evening I'm not sure I can repeat the issue, which makes me nervous about whether I can fix it or not. Quote Link to comment Share on other sites More sharing options...
yorkshire_spam Posted August 27, 2022 Author Share Posted August 27, 2022 (edited) Haven't been able to reproduce the issue either on the drive or on the road. 30 minute thrash along the M1 and then 20 minutes steady 50/60mph along the M62... no sign of the misfire. 😞 and 🙂 I hate tracking intermittent faults. Made a tacho bypass wire and tested that - car runs with that in place. Tested a spare coil and car runs with that in place. But reverted to "original configuration" after testing those, so it's back to how it was on Tuesday. Edited August 27, 2022 by yorkshire_spam Quote Link to comment Share on other sites More sharing options...
Clive Posted August 27, 2022 Share Posted August 27, 2022 7 hours ago, yorkshire_spam said: Haven't been able to reproduce the issue either on the drive or on the road. 30 minute thrash along the M1 and then 20 minutes steady 50/60mph along the M62... so sign of the misfire. 😞 and 🙂 I hate tracking intermittent faults. Made a tacho bypass wire and tested that - car runs with that in place. Tested a spare coil and car runs with that in place. But reverted to "original configuration" after testing those, so it's back to how it was on Tuesday. It's bound not to happen again until you are on your way somewhere important, or it is chucking it down with rain 🙂 1 Quote Link to comment Share on other sites More sharing options...
yorkshire_spam Posted August 27, 2022 Author Share Posted August 27, 2022 1 hour ago, Clive said: It's bound not to happen again until you are on your way somewhere important, or it is chucking it down with rain 🙂 Or half way up a mountain on the 10CR! 1 Quote Link to comment Share on other sites More sharing options...
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