Cylinder1 misfire

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Dave70
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Drives: Mk5 9n 1.2 petrol
Location: South Lanarkshire

Cylinder1 misfire

Post by Dave70 »

Hi ,I have a 2005 1.2 polo petrol ,I'm looking for advice if anyone can help ,about a month ago my management light came on so I put my code reader on it ,cylinder 1 misfire ,got a new Coil pack and problem solved, so I thought yesterday same problem got another coil pack but this time when I ran it for about 15 mins light came back on and shuddering ,when it starts from cold its fine only when it gets up to temperature light comes on and reads cylinder 1 misfire,anybody any ideas what it could be thanx,dave
CarbonChaos
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Re: Cylinder1 misfire

Post by CarbonChaos »

It could be as simply as a failed spark plug ? but im guessing you would have replaced that already
Do a compresion test first ( all cylinders as a compairision ) to check the engine is ok and go from there,injectors dont normally fail but hey its possible

let us know your findings
Johntheo1
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Re: Cylinder1 misfire

Post by Johntheo1 »

Compression test vital as these engines suffered from valve trouble, mine (2005 1.2) did, had to get new cylinder head at ~ 50k miles.
Dave70
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Re: Cylinder1 misfire

Post by Dave70 »

OK got compression test done cylinder 1 90psi don't know about the other 2 ,have changed coil pack, spark plug and injector,it's only coming on sometimes now ,had it out a run today ,done about 10 miles got back in drive and it came on after about 5 mins idling,I switched it off and back on and light hasn't came back on , been sitting now for 20 mins now
CarbonChaos
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Re: Cylinder1 misfire

Post by CarbonChaos »

ok so 90psi is not enough buy a long shot, you dont just check 1 cylinder as this info is pretty useless you need a camparison with the other cylinders.
switching it off and on again just resets the ecu does nothing the clear the fault the light will come back when the perameters are seen again,the only way to resolve this is to find and fix the cause
Johntheo1
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Re: Cylinder1 misfire

Post by Johntheo1 »

My compressions (hot+throttle butterfly fully open) when mis firing commenced were 145/190/195 PSI,

The compression (cyl 1) finally went down to 95psi and, on advice, I replaced the cylinder head rather than repairing the original. The car had only 22k miles up (4 years) but now has 96k miles up and has never missed a beat since, compression test last December gave ~ 200/205 psi for all cylinders.
CarbonChaos
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Re: Cylinder1 misfire

Post by CarbonChaos »

Thanks for that invaluable information Johntheo1 perhaps now the OP will understand the importance of a full compression test and understanding the results, not everything can be solved by tryagnosis

These engines do tend to eat valves and/ valve seats at low mileage
Dave70
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Re: Cylinder1 misfire

Post by Dave70 »

Hi guys I done a compression test my self ,c1 was 125 , c2 was 175 and c3 was 175 but after doing that and putting it all back together I realised that I had not pressed the accelerator when doing it will that give me false reading
RUM4MO
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Re: Cylinder1 misfire

Post by RUM4MO »

Dave70 wrote: Fri Apr 08, 2022 3:25 pm Hi guys I done a compression test my self ,c1 was 125 , c2 was 175 and c3 was 175 but after doing that and putting it all back together I realised that I had not pressed the accelerator when doing it will that give me false reading
Okay, but cylinder 1 pressure is still lower than the other 2, so I would not expect a better set of reading when you keep the TB open.
Dave70
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Re: Cylinder1 misfire

Post by Dave70 »

So I believe that the cylinder 1 has a valve problem and needs a strip down to replace the valve
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