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| Rough Fluctuating Idle below 1000rpm https://www.ausmini.com/forums/viewtopic.php?f=2&t=28561 |
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| Author: | Razor [ Mon Feb 26, 2007 5:11 pm ] |
| Post subject: | Rough Fluctuating Idle below 1000rpm |
I thought might create a new topic instead of putting it under Ford EA Alternator conversion thread. Mods before the problem: Gemini Starter Motor Bosch 85amp Alternator a little rough below 1000 rpm, the idle sounds like its fluctuating badly but its not as bad when you look at the tacho needle. Leave it on idle for a while and it sounds like its going to stall and the idle slowly goes down. Rev the engine and it goes to 1000 - 1100rpm then leave it for like 30sec - 1min and it slowly idles down. No ALT light showing when idling a little rough. Went for a 15 minute drive and same issue when you're on full stop/idling for 30secs and over, other than that drives good. Checked all the wiring and battery cables and everything looks fine to me. I'm getting 14+V on the alternator stud, starter motor, old solenoid & battery terminals. Fan Belt is tight and not slipping, alternator pulley is well aligned with the rest. Any ideas ? |
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| Author: | Timbo [ Mon Feb 26, 2007 5:18 pm ] |
| Post subject: | |
I can't see how its related to the alternator, it should idle much longer than that even if you had no alternator. It sounds more like its running rich and slowly choking up with carbon as it idles. Tim |
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| Author: | Hanra [ Mon Feb 26, 2007 5:25 pm ] |
| Post subject: | |
Yeah thats not related to electrical, thats more mixture/timing/plugs/points..... the list goes on. You wouldnt really want ur idle much lower than 850-900 rpm anyways on a stock motor. |
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| Author: | Mike_Byron [ Mon Feb 26, 2007 7:25 pm ] |
| Post subject: | |
My bet is that the inlet is sucking air somewhere and that the dash pot oil is slowing the piston drop. Quick fix - tipout the dash pot oil and put in transmission fluid, then also make sure the piston is not catching somewhere on the the down fall - adjust the jet position if necessary. Now back to the most likely cause - check all areas, manifold, breather pipe, ets for leaks - if fine then check the carby spindles for wear. Its mostly likely the cause but you need to check the other things first because carby reco's are a bit expensive and a bit fiddly and why spend money if its a inexpensive neglect thing. Your problem is a carby / mixture thing somewhere - dont overlook a catching accelarator cable. |
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| Author: | Razor [ Mon Feb 26, 2007 7:32 pm ] |
| Post subject: | |
I'll set my idle to 850 - 900 rpm then as its running fine there I got ATF in the dash pot I'm just getting paranoid then as I changed these stuff and this issue arises making me think that the electrics is the cause. I'll check for vacuum leak carby & ignition was adjusted and set by TheMiniMan so I'm kinda didnt want to touch or adjust the setting but then again the carby might need reconditioning |
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| Author: | Hanra [ Mon Feb 26, 2007 7:33 pm ] |
| Post subject: | |
Its not electrically related. |
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| Author: | Mike_Byron [ Mon Feb 26, 2007 8:00 pm ] |
| Post subject: | |
In all fairness to TheMiniman, if the spindles were sucking air at the time he tunes the engine then he would have nioticed it and/or commented on it. I still think that your description points towards carby / manifold somewhere. |
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| Author: | Razor [ Mon Feb 26, 2007 8:45 pm ] |
| Post subject: | |
he advised to get the carby reconditioned as he cant tell whats worn & needs replacing without taking it off & open it all up and thats fair and I understand that side. It was running good no complain for me Was very happy about the service I just mentioned that cos the car was running fine till I had electrical problem thats the alternator and earthing issue. I will now concentrate on to carby/manifold/fueling to solve the problem. Thanks |
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| Author: | twintank [ Tue Feb 27, 2007 8:28 am ] |
| Post subject: | |
If you have a positive crankcase ventilation system in your car you might like to check the rubber valve diaphragm for splits or perishing. |
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| Author: | Lillee [ Tue Feb 27, 2007 8:40 am ] |
| Post subject: | |
My Idle is set to 1300 as anything under this will result in the same conditions described by you above. The issue is not really carb related although a bad carb setup will exagerate that to a point. What you have neglected to tell us is whether your cam is std or a reground mild variant. If it is a stock engine, how can you be complete sure that it is stock? I thought my 1098 was stocko but it turns out it was 1152 with a 266 cam... My point is minis are not modern day Vtec's, the cam that runs even in stock motors are not designed to idle at extremely low revs, and if you have a cam of any duration over stock, it will be "lumpy". |
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| Author: | Razor [ Tue Feb 27, 2007 12:09 pm ] |
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I have no idea if my 1275 has stock internal its got twin 1 1/2 SU thats all I know 
The thing is that it was running happily on idle around 700 - 800 rpm before no hiccups and all I changed was the starter, alternator & new 550cca exide battery and now it wont idle like before. yes I've got PCV might check the diaphragm then. |
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