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Engine Stuttering At Low Revs, Especially When Cold


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#76 spiguy

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Posted 15 July 2015 - 10:42 AM

The low tension terminals on the coil might have markings  (+ and - ) though in any case you are better to use the colour of the wires - there should be 2 black and white wires on the negative low tension terminal of the coil, and on the positive there should be a brown with pink tracer. Your suppressor thingy should be fitted to the positive terminal. If it is fitted to the negative, then it will be interfering with the operation of the electronic ignition.



#77 Ozymandias

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Posted 15 July 2015 - 01:17 PM

Checked - it's on the positive terminal.

 

I had a quick look at lunchtime and pushed the HT leads on a bit more/gave them a tweak - started the car, there was no arcing spark and it seemed to rev reasonably alright. No time to do any more than that, but my new coil's arrived, so I'll fit that and hopefully some new HT leads tonight and see if that does it!



#78 spiguy

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Posted 15 July 2015 - 03:05 PM

Fingers crossed for you! hope it's all good. Have you tried running with the noise suppressor disconnected ?



#79 Ozymandias

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Posted 15 July 2015 - 03:30 PM

Not yet - will try this on the way home! :-)



#80 Ozymandias

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Posted 16 July 2015 - 09:03 AM

Touching every kind of wood - I think I've fixed it!!

 

Last night I fitted a new coil, new rotor arm and new HT leads. I also sanded and cleaned all the LT coil leads with isopropyl alcohol.

 

This morning, she's running a treat - good acceleration and no stuttering, even foot down at low revs.

 

The idle's still wavering a little bit, but I probably only notice it because I'm focussing on it.

 

Fingers crossed - I think it might be fixed...



#81 spiguy

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Posted 17 July 2015 - 09:49 AM

Great! Idle will always wander a little, as long as it is 750-950 then the system is doing its thing. Once I was warming the car up on the drive for some reason, popped into the kitchen to get something and when I came out it was idling *perfectly*  - like bang on 800 or so RPM, smooth and steady as a diesel. I stood there for a few minutes and it just kept going that way. I even brought my son out to see it!  Weird!



#82 RooBoonix

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Posted 17 July 2015 - 10:03 AM

Good to hear your car is running better!

That's something mine is good at... Mine idles perfectly according to engine temp. Doesn't hunt at all since I fitted silicone vacuum hoses.. Mine hesitates a bit when cold, think it's air inlet temp sensor.

Good luck!
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#83 Ozymandias

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Posted 17 July 2015 - 10:58 AM

Thanks guys! She's idling between 800 and sometimes fractionally over 1000 when warm - is that still OK?

 

I want to say a massive thanks to everyone who's helped me solve this, especially spiguy, Flying Scot and IainStallard (and also to Sprocket for his excellent tutorial thread).

 

Thanks to you I have not only been able to find and fix the problem (something which a "professional garage with a Mini specialist" couldn't even come close to!), but I now have a much better understanding of how things work under the bonnet, what might be the culprit and what to do about it next time something goes wrong.

 

TMF members, you are the best. Thank you, thank you, thank you!!



#84 RooBoonix

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Posted 17 July 2015 - 11:54 AM

Thanks guys! She's idling between 800 and sometimes fractionally over 1000 when warm - is that still OK?
 
I want to say a massive thanks to everyone who's helped me solve this, especially spiguy, Flying Scot and IainStallard (and also to Sprocket for his excellent tutorial thread).
 
Thanks to you I have not only been able to find and fix the problem (something which a "professional garage with a Mini specialist" couldn't even come close to!), but I now have a much better understanding of how things work under the bonnet, what might be the culprit and what to do about it next time something goes wrong.
 
TMF members, you are the best. Thank you, thank you, thank you!!


When hot mine drops down to 650-700rpm. It doesn't always go that low and sometimes takes a few seconds before it drops down from 800ish to 650

#85 spiguy

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Posted 17 July 2015 - 12:03 PM

Glad to help. Don't forget though that in the end you solved it yourself!  I would use the car a bit and give it a few long runs and see where you are. When warm it shouldn't really be above 950, though it depends on what you are doing, state of the battery etc. If the car was left sitting in the drive running, up to temp, it should really drop to about 800 RPM ish, and be fairly steady  - maybe +/- 50RPM. It shouldn't hunt up and down between 700 and 1000 for example. However as you have found various issues, and been tinkering etc then maybe it needs some time and good runs to clear everything out and for the ECU to re-learn the idle control.

 

If in doubt, post a video up for comment, as it is much easier to understand what it is doing that way.



#86 IainStallard

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Posted 17 July 2015 - 12:22 PM

Pop over and I'll reset your ECU using my fault reader, that should then allow it to relearn the engine and with any luck, should all return to normal!



#87 firstforward

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Posted 17 July 2015 - 02:58 PM

Ozymandias I have an SPi with air con and have not been able to find a HT lead for No1 cylinder, nearest the alternator. As you will know it needs a 60 degree or thereabouts angle to miss the alternator. Where did you get your set from? or am I wrong will a 90 degree  or straight will fit?



#88 Ozymandias

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Posted 17 July 2015 - 03:21 PM

firstforward, I ordered these ones from Minispares and they fit/work just fine - admittedly No 1 is a bit squished against the alternator bracket, but the old one was too!

 

If you find a 60 degree or straight one, do let me know, the current arrangement is probably not ideal... but it does work!



#89 spiguy

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Posted 19 July 2015 - 10:06 PM

My no 1 lead lies on top of the alternator, but is not long enough to ever wander over far enough to foul the rotating pulley / fan of the alternator. My leads are just a standard lead set from minispares. I have always run my leads that way and never had any issues with it.



#90 firstforward

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Posted 07 August 2015 - 08:17 PM

My no 1 lead lies on top of the alternator, but is not long enough to ever wander over far enough to foul the rotating pulley / fan of the alternator. My leads are just a standard lead set from minispares. I have always run my leads that way and never had any issues with it.

 

Do you have an SPi with air con? It is the fact that the alternator is located so high blocking the number 1 spark plug so a plug lead with an angle is required to avoid the alternator, also I have had to make up a special socket to remove or tighten that plug as there is not enough clearance for a straight line socket.






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