Technical Fiat Panda 1.1 unstable RPM

[Maatias]

Hello, this is my first forum in here.
I have a Fiat Panda mk2 1.1 2006.
My family has owned this car for about 6 years and has also become my first car.
The car always had issues with passing NCT (Irish MOT) due to fluctuating RPM at 3000 to measure emissions.
I decided to finally investigate this issue since it has not passed again and I would like to sell the car.

I have attached a video of the problem. A slight vibration can be felt as the car runs, feels like one of the cylinders does not go off and then works and does not after a few seconds as can be seen on the video.
I have attached the DTCs that have showed up.

P0351 DTC: After opening the bonnet I could hear an electric clicking noise coming from the ignition coil area. I have replaced one of the coils, the noise is gone and so is the DTC.

P0120 DTC: I have removed and cleaned the throttle body and the sensor. The car accelerates better and the DTC is gone.

"00,1d,d7,00(U1700)" : I have no idea about this one. Some sort of a short, will investigate later.

However the fluctuating RPM still persists.
I have removed and inspected the spark plugs and found no issues with them (attached pictures of them). They were replaced less then 5,000km ago, so were the coil cables and the coils (minus the one I just replaced)

I will take out and inspect the oxygen sensors when the weather allows it.

Any help will be appreciated.
Thanks

 

[koalar]

P0120 DTC: I have removed and cleaned the throttle body and the sensor. The car accelerates better and the DTC is gone

Probably the source of your fluctuating RPMs as well

Flyby wire throttle or cable throttle body

 

[koalar]

U1700

Normal, ignore it

 

[Maatias]

View attachment 460811

Probably the source of your fluctuating RPMs as well

Flyby wire throttle or cable throttle body

Hello and thanks for the quick answer, I have cleaned the sensor and the whole throttle body and the DTC no longer comes back, so I don't that is the problem.

 

[koalar]

Hello and thanks for the quick answer, I have cleaned the sensor and the whole throttle body and the DTC no longer comes back, so I don't that is the problem.

You clear the code and it not triggered again

But P0120 is not the throttle body

Is your throttle flyby wire or cable operated

 

[Maatias]

You clear the code and it not triggered again

But P0120 is not the throttle body

Is your throttle flyby wire or cable operated

Yea, deleted the code and it does not come back
Cable operated.

 

[koalar]

Photo one plug looks wet with fuel

 

[Maatias]

Photo one plug looks wet with fuel

Petrol Injector faulty?
I think I heard about the O rings going bad

 

[koalar]

Probably not firing correctly

The coils normally out last the car

They normally go bad, if the plug gap go too big or the HT lead goes faulty

What is the gap

 

[Maatias]

Probably not firing correctly

The coils normally out last the car

They normally go bad, if the plug gap go too big or the HT lead goes faulty

What is the gap

I will check for the gap tomorrow, thanks for the answers

 

[DaveMcT]

The ignition coils on Mrs Dave's 1.2 were replaced at 70K miles. Fault code showed one had gone down. I also replaced ignition leads. Spark plugs were also replaced but the originals did not look bad. No problems since. Coils are very cheap.

100HP needed a set of plug top coils at not many more miles. I found the culprit with an IR thermometer to watch the exhaust manifold stub temperatures as they warmed up. You can also wet the exhaust manifold (cold) and see which one takes longest to dry out. But then you can't quickly prove it by moving a coil.

 

[koalar]

A quick comparisons, the plugs don't appear too wide not exactly scientific
New plug

Yours

A measure would be better though

They should start at .8-1 mm depends on make and start to fail at at 1.6-1.8 mm


Check there isn't a large air leak between the inlet and head

Check all the cylinders are firing, yours will be slightly different as the coils are on the right not under the air box

If they are not check you have a strong spark at each

Make sure the spark has an easier path to ground than through you, then you will not get zapped

In your scanner

What's the long term fuel trims at idle and at 3K rpm, misfire it will be well positive

What's the manifold pressure before you start engine, does it match what Google say the pressure is, what's the pressure at idle

What the ambient temperature before you switch the engine on, does it match what Google says the temperature is

Is the coolant temperature reading right


What's the MAP sensor looking like, it's not covered in oil

Like this one someone posted earlier

 

[Maatias]

A quick comparisons, the plugs don't appear too wide not exactly scientific
New plug

View attachment 460834
Yours


View attachment 460835


A measure would be better though

They should start at .8-1 mm depends on make and start to fail at at 1.6-1.8 mm


Check there isn't a large air leak between the inlet and head

View attachment 460836


Check all the cylinders are firing, yours will be slightly different as the coils are on the right not under the air box
View attachment 460838


If they are not check you have a strong spark at each

Make sure the spark has an easier path to ground than through you, then you will not get zapped

View attachment 460837
In your scanner

What's the long term fuel trims at idle and at 3K rpm, misfire it will be well positive

What's the manifold pressure before you start engine, does it match what Google say the pressure is, what's the pressure at idle

What the ambient temperature before you switch the engine on, does it match what Google says the temperature is

Is the coolant temperature reading right


What's the MAP sensor looking like, it's not covered in oil

View attachment 460841

Like this one someone posted earlier

 

[Maatias]

Hello,
Last weekend I have checked and cleaned the two oxygen sensors, checked the seals on injectors and all was good and the issue persists.

I will check the spark plug gap, the manifold pressure and the MAP sensor like you say. Hopefully this weekend if it does not rain.
I talked to some lads at work and one of them suggested an air leak somewhere, could be like the one you mentioned here at the inlet and head.

and thank you for the replies.