my daughter has an m reg micra which has developed a really bad mis-fire when it gets hot.
i've changed the distributor, checked hoses for vacuum leaks and re-gapped the plugs, removed the air filter.
the blink codes for diagnostic don't work!
getting stuck now, any ideas please?
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I once helped a neighbour solve a similar problem albeit with a different type of car.
To prove if the problem related to just one cylinder or not, one by one we unplugged a high tension lead from the spark plug it normally attached to, and reattached it to a "spare" plug with the thread "earthed" against the engine block (this ensured that the HT had somewhere to discharge properly).
Repeated cylinder by cylinder we proved that indeed the misfire did relate to only one specific cylinder; when this HT lead was disconnected the misfire remained the same rather than getting worse as when others were removed. It turned out to be a duff plug that electrically broke down with temperature.
Plug changed, problem solved.
Just a generic idea to try.
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Well, I would say it is something on the HT side:
Leads
Plugs
Coil
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i've changed the plugs, the coil is built into the distributor (and I've replaced that with a second hand one - no change), the HT leads well, may be.
I took it up the road after changing the plugs, on tickover it's a smooth as silk, set off up the road and it's fine for a few seconds then it misfires (or so it seems) really badly, back off the gas and slip the clutch and it goes back to a good tickover then it's ok for a few more seconds????
In the short term as it only does it when it's cold i'm thinking about removing the thermostat to keep the engine cool.
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Sounds like HT side failing under load to me (spark firing voltages rises with engine load - hence HT weak spots fail under load).
I wouldn't remove the thermostat.
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Sounds like HT side failing under load to me (spark firing voltages rises with engine load - hence HT weak spots fail under load).
if it's the ht leads failing under load wouldn't it do it when it's cold as well? as it stands it pulls ok until the engine warms up!
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Exactly the same problem last year.Nothing would fix it, until I put a secondhand O2 sensor in from a scrapyard.Lovley little car now 5 minute job,the sensor is right in front of you when you open the bonnet.No lights on dash to say it was faulty either!
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If it isn't the O2 sensor, it might be the throttle body; have a look here...
www.honestjohn.co.uk/forum/post/index.htm?f=4&t=39...2
...but be aware these are available from a number of sources (e.g. eBay) at lower prices.
Please can you post a follow-up to let us know how you get on, as we have a Micra in the family and if it turns out to be an inherent fault I'd be grateful for your experiences.
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Throttle Body problems are well known with Micra's Before you spend any money they often just need to be re-soldered (the original joints just dry out).Have a search on 'ciscos micra files' check spelling! There is a step by step how to do it -Its very easy-Good luck.
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...and if you click on the link of my previous post, you will indeed see a link to these step-by-step re-soldering instructions...
(can anyone provide links/details to an "adjustment/calibration" procedure, just in case one ends up screwing up the potentiometer adjustment altogether...?)
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Get the car in somewhere dark, open the bonnet, get someone to rev and look for tracking up the plug leads,the insulation breaks down, you will see small blue flickers.
Watch you dont gas yourself though.
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