Technical Misfires at high rpm, sometimes 1.2 (2012)

[mario05]

Hello
I have a problem with my Fiat punto 1.2 (2012). I just bought it two months ago, so I don't know much about the maintenance history. The issue is that sometimes when the car is warm and I am driving on the highway above 3500 rpm, the engine management light comes on and it goes into limp mode. It is not always the case, and I can often drive 25 km above 3500 rpm and everything goes well. When the car goes into limp mode, I can immediately turn the car off and on again, and it works normally. I don't really know what it is myself. The error codes that came up are p0300 and p0302. Now, the garage has also reported that it had a misfire in the third cylinder. I replaced all the spark plugs and ignition coils, but that was not the problem. The cables between the spark plugs and ignition coil have also been replaced, and a cleaning agent has been added to the fuel.
What could be causing the issue? What steps can I take to see what is causing the issue?

I would really appreciate your help.

 

[jackwhoo]

Does the mil flash when fault occurs ? Or is it on without flashing?

 

[mario05]

yes the engine light was flashing.

I don't know if it has anything to do with it, but once when I was standing still after a ride the rpm was not constant. you can see it in the video

 

[AnthonyH]

Maybe the fuel injectors are blocked?

 

[mario05]

Is there an easy way to check that?

Is it possible that the misfires occur consistently after about 25 km?

 

[GrandePunto PL]

Yes. For example fuel tank can develop some pressure/vacuum during operation. Venting of the tank is faulty somehow.
Easiest check ever, if power loss occurs: you undo the fuel cap (ideally on running engine - spare key needed).

 

[jackwhoo]

Could need a phonic wheel relearn.

When was timing belt last changed?

 

[mario05]

The timing belt is replaced 30,000km ago. but I don't know if the previous owner also had problems with it.

Tomorrow I will check whether the fuel tank has a vacuum.

 

[jackwhoo]

When engine at normal temperature, mil flashing, car stopped, gear box neutral , hand brake on , rev engine to about 6000 rpm for 2 seconds, allow revs to drop to idle speed,wait a few seconds.
repeat twice more, switch off engine , wait 1 minute before restarting engine.

Phonic wheel learn done. Fingers xed problem fixed.

 

[mario05]

I checked yesterday to see if there was a vacuum in the fuel tank, but that was not the case.

Could it be something to do with the fuel filter?

 

[jackwhoo]

Do the phonic wheel learn

 

[mario05]

when should I do the phonic wheel learn?
If the car breaks down during misfires. Or do I need a device for it?

 

[jackwhoo]

when should I do the phonic wheel learn?
If the car breaks down during misfires. Or do I need a device for it?

Post number 9

No device needed

 

[mario05]

The last time I couldn't get the engine above 3500 rpm when the engine light was flashing.

But I'll try again next time.

 

[jackwhoo]

The last time I couldn't get the engine above 3500 rpm when the engine light was flashing.

But I'll try again next time.

If engine won't rev past 3500 rpm gear box in neutral then problem is not phonic wheel learn.

Good luck with fixing .

J

 

[GrandePunto PL]

Limits about 3000-ish RPM are about VVT for example (mechanical, hydraulic or electronics issue)...

 

[mario05]

Could it be that the rpm is limited by the misfires?
What could be causing the misfires? fuel filter?

 

[GrandePunto PL]

Lack of: air, fuel, compression, spark energy. Then timing, valves (but it's under "compression" category).
Easiest engines on the planet (last ones). You learn it NOW as a beginner/hobbyist or don't touch the cars at all if you fail at diagnosing a Punto!