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| Missing and inconsistant idle? https://www.ausmini.com/forums/viewtopic.php?f=2&t=97639 |
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| Author: | phillb [ Mon Aug 13, 2018 11:22 am ] |
| Post subject: | Missing and inconsistant idle? |
I'm have 2 really annoying issues with my car at the moment. I don't think they are related but interesting if anyone has any suggestions for either of these issues. Car has electronic points and black box. a) missing occasionally, worse when cold. Very sudden and the tacho needle always drops at the same time. sometimes it will be idling and it will just miss every few seconds. Other than this the idle and running is very smooth. b) sometimes after decelerating eg pulling up at the lights the idle will drop right down, sometimes stall. Seems to be more likely to happen if I I can also make this happen if it is idling (and it idles perfectly smoothly otherwise) and I give the throttle a little "jab" and it will sometimes drop in idle speed nearly stalling then come back up to idle perfectly. I have double checked all the linkages and springs (twin SU) and nothing is binding. Thanks in advance. |
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| Author: | Bill B [ Mon Aug 13, 2018 12:02 pm ] |
| Post subject: | Re: Missing and inconsistant idle? |
Random thoughts: *1 of the carb pistons not dropping smoothly? *interruption to petrol supply - intermittent pump or float bowl needle/seat fault? These odd things are frustrating - probably will turn out to be lose wheel nuts or whatever.... |
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| Author: | timmy201 [ Mon Aug 13, 2018 12:05 pm ] |
| Post subject: | Re: Missing and inconsistant idle? |
Is the PCV working as it should Damper oil level in carbs Low tension wires on the coil loose? Do the plugs look OK when you get the missing at idle? |
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| Author: | phillb [ Mon Aug 13, 2018 12:26 pm ] |
| Post subject: | Re: Missing and inconsistant idle? |
Bill B wrote: Random thoughts: *1 of the carb pistons not dropping smoothly? *interruption to petrol supply - intermittent pump or float bowl needle/seat fault? These odd things are frustrating - probably will turn out to be lose wheel nuts or whatever.... Ta, already checked pistons and the float needles were another I thought of so I will check these. Will check out pump and connections too. Thanks |
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| Author: | phillb [ Mon Aug 13, 2018 12:30 pm ] |
| Post subject: | Re: Missing and inconsistant idle? |
timmy201 wrote: Is the PCV working as it should Damper oil level in carbs Low tension wires on the coil loose? Do the plugs look OK when you get the missing at idle? Thanks Pcv I recently cleaned but I will recheck. Dampers I checked I checked for good connections at coil I'll recheck the plugs next time it misses but thay are usually pretty consistant |
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| Author: | Bill B [ Mon Aug 13, 2018 12:37 pm ] |
| Post subject: | Re: Missing and inconsistant idle? |
Don't assume spark plugs are reliable! Spent months rechecking everything for a miss on load. 1 faulty plug (first time I used Bosch, too). |
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| Author: | phillb [ Mon Aug 13, 2018 3:57 pm ] |
| Post subject: | Re: Missing and inconsistant idle? |
Bill B wrote: Don't assume spark plugs are reliable! Spent months rechecking everything for a miss on load. 1 faulty plug (first time I used Bosch, too). Actually its funny because I fitted new plugs recently and it initially seemed to help but the problem has slowly returned. If a plug or a lead was faulty would it also cause the tacho to be effected? A few times when it has happened badly while driving the tacho was jumping all over the place. |
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| Author: | drmini in aust [ Mon Aug 13, 2018 5:26 pm ] |
| Post subject: | Re: Missing and inconsistant idle? |
If tacho is jerking it's a low tension fault somewhere. Check the spade connectors on the fuse box and ignition switch. It could be a loose or dirty contact in the switch also. I changed all my coil spade lugs for ring terminals to avoid dodgy connections there. |
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| Author: | phillb [ Mon Aug 13, 2018 7:24 pm ] |
| Post subject: | Re: Missing and inconsistant idle? |
drmini in aust wrote: If tacho is jerking it's a low tension fault somewhere. Check the spade connectors on the fuse box and ignition switch. It could be a loose or dirty contact in the switch also. I changed all my coil spade lugs for ring terminals to avoid dodgy connections there. Thanks. I had already checked and tightened the coil ones but I hadn’t thought of all the others that could be involved. Sent from my iPhone using Tapatalk |
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| Author: | Ian_B [ Mon Aug 13, 2018 9:06 pm ] |
| Post subject: | Re: Missing and inconsistant idle? |
Tacho going missing Spark loss Ignition system. My two bobs. |
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| Author: | phillb [ Tue Aug 14, 2018 7:44 am ] |
| Post subject: | Re: Missing and inconsistant idle? |
Thanks for all the suggestions. So last night I tightened up the connections at the coil, fuse box and ign switch. Also cleaned up the fuse box a bit. At 50years old its looking a bit tired so I prob should replace it. There were a couple of not so tight spades at the ign switch and fuse box. I found after doing all this it was improved but not totally cured. Took it for a drive but it still missed a few times when cold but it didn’t seem to do it as much and not at all once fully warmed up. I might swap to a spare distributor cap an lead set and see what effect that has. The other problem with the idle is no different. I have noticed it happens mostly if I have decelerated to a stop using engine braking. Even worse if I have decelerated down a long hill. The motor will nearly stall, sometimes it does. Mostly it it just recovers by itself to a perfect idle. As mentioned a light jab of the throttle at idle will also bring about the same issue. I plan to check the float needles but interested in any other suggestions. The carbs were overhauled only a few years ago with the shafts and butterflies all professionally installed. The problem has also come about suddenly not gradually. Cheers Sent from my iPhone using Tapatalk |
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| Author: | brett [ Wed Aug 15, 2018 11:05 am ] |
| Post subject: | Re: Missing and inconsistant idle? |
Poor fuel? or crud in the float bowls. also the float needle thing can stick and cause issues |
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| Author: | phillb [ Wed Aug 15, 2018 11:26 am ] |
| Post subject: | Re: Missing and inconsistant idle? |
brett wrote: Poor fuel? or crud in the float bowls. also the float needle thing can stick and cause issues Fuel is fresh. Yes, Checking the floats needles and bowls is next on my list A MITG member suggested it may be a vacuum leak eg PCV diaphragm. Or perhaps the one way valve in the brake booster. Diaphragm was ok but found loose pcv hose and the oil cap loose. There’s been some improvement since fixing those things. Still need to check the booster. For those on Facebook I might post a video of what it is doing. Sent from my iPhone using Tapatalk |
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| Author: | Morbo28 [ Thu Jul 30, 2020 6:36 pm ] |
| Post subject: | Re: Missing and inconsistant idle? |
Phill, just wondering what was the cause and solution to this issue in the end? |
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| Author: | phillb [ Thu Jul 30, 2020 7:34 pm ] |
| Post subject: | Re: Missing and inconsistant idle? |
It seemed to very gradually improve. Although very very occasionally I still get a little miss here and there. The fact that with many new fills of fuel maybe there was water or contamination. Sorry was one of those situations with no clear answer. Sent from my iPhone using Tapatalk |
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