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Old 16-08-2017   #1
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Odd Misfire issue

Hello,

First time posting.
I have a Fiat Punto 1.2 8v 2012 with 65k on the clock.
I get a P0304 and P0300 code randomly and don't notice any issues when driving. However when on the motorway for an extended period of time ie 1hour The car randomly goes into Limp Mode. I have replaced the Coil Pack, HT Leads, Spark Plugs, and now Crankshaft sensor. I have cleaned out the Throttle body and the MAP sensor but the car is still misfiring and going LIMP on the motorway. I have also checked the oil and the Cam belt has already been replaced (the issue occurred before the Cam Belt was changed)

I have also noticed that when I start it it seems to idle fine but after a drive when the engine is warm it seems to shake a little more but does not Hunt

Is it possible to remove the injector on Number 4 and replace it with Number 1 to test the Injector or do I have to replace the entire rail.

Any sensible ideas at this point would be much appreciated.

Regards
FDW
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Old 23-08-2017   #2
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Re: Odd Misfire issue

I have since reset the ECU by removing the battery terminals and shorting them for 30 minutes

I also switched the injectors from cylinder 1 to 4. I haven't reset the errors with my obdii connector as I wont have it till this evening but the Logic is

If I clear the errors and it still errors on 4 then its not the injectors it has to be wiring, or ECU (or Mechanical)

If it errors on 1 and not 4 then we know its the injector

If it doesn't error at all then we know the ECU reset has fixed the issue.

If it errors on both then,... well that will be a pain means an injector was either put in wrong or I have broken one and the other issue still remains.


I have noticed now though that so long as I do not push the revs over 4.5k on the motorway then the car will not go into limp mode. But If I accelerate from stopped to 70 as fast as possible then it will.
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Old 24-08-2017   #3
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Re: Odd Misfire issue

Just a quick update.

While checking the car last night for possible vacuum issues I noticed my backbox (rear silencer) is blowing, and from the look of it seems to have been blowing for a while, Its making a popping noise as well so I think the baffles are duff, Replacing this on the weekend.

Still not sure if the codes original P0300 and P0304 codes have come back but hoping once the backbox is replaced that it wont idle so rough.
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Old 26-08-2017   #4
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Cool Re: Odd Misfire issue

Ok so after running it for a little while I wasn't getting any codes so it seemed as though the issue was resolved. I decided to give it a good test before I decide the cars worth cleaning again.

I floored it all the way to ,... a high enough speed under a heavy load and this time I could actually feel it misfiring.

I held out at ...a high enough speed for long enough and the car went into Limp mode and started to power down, It took a little while but eventually the codes came up as P0300 and P0301 meaning the issue was now on the 1st Cylinder and not the 4th

And seeing as the only specific change I made was to switch the injectors from position 4 to 1 It has to be the injector that's faulty.

So it sucks that I changed the entire ignition system but atleast I have spares.

All I need to do is buy 4 new injectors and and a backbox and the car is all sorted
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Old 08-09-2017   #5
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Re: Odd Misfire issue

Hello,

Just a quick update. Used a cheap tool from Ebay to clean the injectors with carb cleaner, Put them back in and took them for a quick spin.

Tried really hard to get it to misfire doing what I did before and nothing.

Bit to soon to tell but seems like its sorted now.

I have also noticed that my new backbox sounds really really bad, not sure if the car is still running rough or it is the backbox.

I hope this helps someone else diagnose issues in the future.
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Old 08-09-2017   #6
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Re: Odd Misfire issue

Thanks for the posts and updates.
If you do end up needing a injector replacement you don't need to change all 4 just the faulty one.
Good job.
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Old 02-10-2017   #7
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Re: Odd Misfire issue

Hello,

After trying to clean the injectors It seemed to work but then the issue came back.

I bought a cheapo Multi-meter to test the solenoids and also bought 2 second hand injectors for 6.50 each ( similar amount of mileage as mine) as Fiat wanted 120 for one new injector which seemed ridiculous seeing as the faulty injector lasted less that 50k miles. (less mileage than my uridium spark plug costing 12)

My friend had recently changed 1 injector of four and because one was new and 3 were old the engine ran unevenly. I would recommend if replacing one old with new you replace all.

In my case I cleaned all the injectors first with an injector cleaning kit from ebay for around 5 plugged them in and the engine started with no issues at all and now runs like a dream.
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