Technical Misfiring when starting hot engine

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Technical Misfiring when starting hot engine

MK2lover

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Hello,

My beloved Fiat Punto 2005 Mk2 5 doors with 60 BHP is playing games with me.

It started misfiring and showing error code P0352 (Ignition Coil B Primary/Secondary circuit). I googled the problem and replaced both Ignition Coils which solved the problem for ~1.5 weeks.

The problem is now back, with the engine misfiring on 2 cylinders. The error code has remained the same (P0352). The problem seems to only occur when the engine is HOT, turned off and started again. If I let it cool down the problem goes away.

What is most likely to be broken?
Wiring
ECU
Spark plugs
 
Change the HT leads and the spark plugs now.

Makes sense to do the cheap stuff.

I had a misfire on cylinder 2 recently and got a new coil pack, HT leads and spark plugs for around £50. Makes sense to do them all at the same time.
 
Hello,

My beloved Fiat Punto 2005 Mk2 5 doors with 60 BHP is playing games with me.

It started misfiring and showing error code P0352 (Ignition Coil B Primary/Secondary circuit). I googled the problem and replaced both Ignition Coils which solved the problem for ~1.5 weeks.

The problem is now back, with the engine misfiring on 2 cylinders. The error code has remained the same (P0352). The problem seems to only occur when the engine is HOT, turned off and started again. If I let it cool down the problem goes away.

What is most likely to be broken?
Wiring
ECU
Spark plugs


As others have said, it's wise to change leads and plugs if a coil pack fails. If a lead or plug is faulty (high impedance) the HT voltage will rise and this stresses the coil. Not much of an issue with the old style oil filled coils but can cause insulation failure in the modern moulded ones. New coil works for a while then goes same way. Change leads and plugs first maybe the coil survived. This is one case when some suppliers policy of not taking electrical parts back has a sound basis. Note that the ECU sees higher voltage too but has protection components, these can only take so much though and if they fail it's a new ECU. This is also why you should not disconnect the HT leads on a modern car.


Robert G8RPI.
 
I've changed the leads, both ignition coils and the plugs, but the problem still remains :(

However, I am now 99 % certain that the problem only occurs when the engine has been running for +20 minuttes (the car is as hot as it gets), then turned off and started again. Is it possible that a broken censor is turning of the fuel supply for the 2 not running cylinders?

Or is a new ECU the next step? (They're expensive...)
 
Here is what we just went through with daughters car, misfiring when hot then just misfiring, touchwood it has been fine now after a loose plug on l/h/s of ecu,still keeping an eye on it as dont know if we are out the woods yet
This miss and missfire was intermittent at first but only with a hot engine, it then decided to say hello permanent it might help
John
https://www.fiatforum.com/punto-ii/442231-ecu-not.html
 
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Hmm... Mine is also starting to idle poorly now. Goingup and down in reps. For some odd reason it idles as it should if I turn of the headlights? Electrical problem?

Should the next step be to change the ECU? If so can I settle for an ignition ecu module?
 
It could still be the coil. The new one might be faulty? Also, are spark plugs the correct type/gap for the car?
 
I've replaced both coils with entirely new ones. They looked perfect, and are from a trusted seller. It made no difference to the problem at all. I could reinstall one of the old coils, but I highly doubt that they're faulty.

I think I'l look for bad ground connections this weekend. Does a complete list/map/picture of all GND/VSS connections for a mk2 exists?
 
Once had an issue with a car that ran fine when cold, but misfired when engine was warm. It also didnt start very well when engine was at normal operating temperature. Turned out to be a hairline crack in the Inlet Manifold.
Basically the crack opened when the engine was warm due to metal expansion.
 
Had similar issues with my old 2004 Mk2 Active Sport 1.2 8v. Would 'purr' when idle sometimes, mostly on cold days. Dropping revs when idle and jerking when pulling away sometimes. It looked nice and was cheap on insurance for a 17/18 year old. I'm not a mechanic but have you tried a hammer? :D
 
I've replaced both coils with entirely new ones. They looked perfect, and are from a trusted seller. It made no difference to the problem at all. I could reinstall one of the old coils, but I highly doubt that they're faulty.

I think I'l look for bad ground connections this weekend. Does a complete list/map/picture of all GND/VSS connections for a mk2 exists?[/QUOTE

Yea bought a few coils myself, never cured anything, infact I had to buy a new ECU, left the old coils in just to prove to myself coils don't blow ECU's. That was 8 months ago, weak battery can cause voltage spikes, if turning H/lights off improves things better get a new battery, too late if the ECU has gone but they are cheap.
 
Bought a refurbished ECU online for 70 GBP

Disconnected the battery
Changed ECU
Connected the battery

Started the car
3 Error lamps showing (P0530, P0115, P0120)
Car slowly started up and after 5 sec. ran fine
Erased error codes
Restarted car
Car has been running perfectly both idling and driving eversince :)
 
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I meassured the voltage and the voltage seems to be pretty stabile (+-0.1V)
 
It hadn't been on for 5 days, so it was probably the battery.
 
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