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Old 2 Weeks Ago   #1
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Mk2 punto misfire

Hi,still having problem with this misfire.
I have new leads,plugs,and coilpack changed last year.
When the engine is cold there is no misfire.
After 25 minutes when engine is hot,it misfires when i change down a gear
for about 1 to 2 seconds then full power again.
So the problem happens when engine is hot,what does this indicate???
tony
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Old 1 Week Ago   #2
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Re: Mk2 punto misfire

Check the other thread
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Old 1 Week Ago   #3
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Re: Mk2 punto misfire

Resistance is greatly affected by heat, I would look for a dodgy sensor. Cam or crank, might be worth a look as they are close to the main heat source.
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Last edited by puntoFix; 1 Week Ago at 20:41.
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Old 1 Week Ago   #4
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Re: Mk2 punto misfire

Vacumn/air leaks are more noticeable at low rpm but as you see it when hot suggests a hole is opening when hot which would be odd or your idle valve or throttle position sensor is dodgy when hot.
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Old 1 Week Ago   #5
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Re: Mk2 punto misfire

if the sensor is effected by heat i would have the misfire all the time when the engine heats up.
it only misfires for 1 to2 seconds when i accelerate when engine is hot.
tony
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Old 1 Week Ago   #6
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Re: Mk2 punto misfire

Does it not do when at idle with a hot engine.
If you rev it from idle to say 2000 rpm at a parked position does it still do it?
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Old 1 Week Ago   #7
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Re: Mk2 punto misfire

IT generally doesnt misfire if i rev the engine when not under load.
it was bad last nite in 2nd gear,it took about 5 seconds for the misfire to clear,
if i hit the accelerator hard when its hot its bad,if i go gently its sort of ok.
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Old 1 Week Ago   #8
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Re: Mk2 punto misfire

If it only does it under load then it may be ignition system, I know you changed coils plugs etc.

Id start by checking resistance of coils see if there still on spec and you can do a quick check by removing the lead at the coil and diverting it to the chassis with a test light wire to see how far the spark jumps, that gives you a good indication of its strength, dont do it to battery terminal do it to chassis point away from battery you dont want battery to explode or if you have a pace-maker:-) do it when cold and see how far you can get then when hot. obviously its not under load but will give you and idea.


Only when hot, underload and not all the time and clears it self after a while. Its going to be tricky to test in all thoese conditions, so it might be the case you will just have to be a 'parts changer' just to find the problem.

Amazon has an amazing returns policy :-) Buy a good brand coil run it, change it to over bank, try new leads buy some NGK plugs.

Alternativly you would need to run a oscilloscope on the the ignition whilst driving it, which is doable but not ideal.

I have a Hantek 8 channel one but I never used it when driving only when parked up.
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Last edited by puntoFix; 1 Week Ago at 12:04.
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Old 1 Week Ago   #9
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Re: Mk2 punto misfire

I have the old coil pack at home,would it be worth trying that one,and if it solves the problem,i can go and buy a good quality new one,
Thanks for all your help,
tony
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Old 1 Week Ago   #10
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Re: Mk2 punto misfire

You can use the old one but you must have replaced them for a reason so its a unknown, at least with a new decent brand you would hope its OK. Its very easy to change them over but if the original one makes no difference try a new one.

Bosch one for 14
https://www.ebay.co.uk/itm/FIAT-PUNTO-176-188-Ignition-Coil-1-1-1-2-93-to-10-Bosch-46543562-46548037-New/232413826526?epid=5017013833&hash=item361cf18dde:g :tVoAAOSw3QpZbSRT:rk:1f:0

Better ones are Champion, MAgneti ,Beru etc ie cost more.


You will need a multi-meter preferably digital and get a decent 12v test light.

Check battery voltage both with car off and under electrical load, you can go a to local motor parts shop and they usually can check a battery for free. Make sure battery is working by turnign engine on and putting everything on lights fans power steering everything and make sure the alternater is working and battery is charging OK and has enough voltage ie (see video below), to run everything.


Alternator should produce enough charge to cope with load, fix/replace these if any problems.

Test resistance of coils and do the spark gap test with test light.


if nothing noticable then I would buy a new decent coil and test on both sets of cylinders. to see if it fixes it but it could be faulty lead or not sitting on sparg plug correctly or bad plugs seems most people recomend the original NGK ones you can buy a set for 8 of ebay inc shipping.
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Last edited by puntoFix; 1 Week Ago at 17:29.
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Old 6 Days Ago   #11
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Re: Mk2 punto misfire

i have tried 2 coil packs and still the same problem.
leads and plugs also changed.
It sounds like a 2 stroke engine when it misfires after about 8 to 10 miles into a journey,but only when i change down and apply a bit of power,it misfires for 2 to 3 seconds and then goes back onto full power,still cannot pinpoint this problem.
tony
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Old 5 Days Ago   #12
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Re: Mk2 punto misfire

hi,still getting this stupid misfire when engine warms up,its getting worse now,
any ideas how to fix it,getting desperate for help!
tony
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Old 5 Days Ago   #13
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Re: Mk2 punto misfire

Ok. So you have changed all of the obvious stuff related to SPARKS.

If it starts well.. you have the basics covered.

Your initial post discussed oil consumption.. has this been overcome?

I am left thinking the HOT engine misfire is through poor fuelling.

Deos the temp gauge look right. Fan cuts in as normal..?


When did you last get the emissions tested?

I am thinking Lambda..
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Old 5 Days Ago   #14
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Re: Mk2 punto misfire

It might be time to take to a mechanics. Or get a mobile diagnostic to come and have a look, they will have all the kit to find the problem. It sounds electrical to me something when hot and under load, bad ground or dodgy resistance in a part.
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