Technical Random check engine

[Maryland31]

Hi, first time posting here
I have this issue that nobody is able to figure out so idk what to do.

I have this 2014 (pre-facelift) Fiat 500 Sport with the 1.2 petrol engine, the car runs smooth but sometimes (lately has become more frequent) on start (doesn’t matter if engine is warm cold or in between) the engine light comes on, engine misfires but only 2 seconds or so, then the engine starts starts running normally and the engine light comes off ( no error is stored, checked with cheap obd and checked by official fiat dealer)

Also, this is rarer, running at road speeds, nothing out of normal 80-120 km/h the check engine light comes on, the car looses a lot of power and starts misfirng for a few minutes or until restart, after that again all normal no codes saved on ecu.

Im really desperate on this because car is still in warranty from the dealer and seems like a very starnge and expensive issue to tackle

Ps. Im not a native english speaker, my apologies for the bad spelling.

 

[The Panda Nut]

These sorts of problems are usually simple things and a dealer should be able to sort it out so ask there first before doing work that could invalidate the warranty. The 1.2 is generally reliable.

There are a few simple things that you can do to improve general running. Ive had my share of odd running with our late Panda 169. The MAP sensor is prone to getting fouled with oil. it sits in the inlet manifold. Left side as you look from the front. It has a wiring plug attached and its held in place by one screw. Remove it and clean with some carb cleaner spray. Also make sure the throttle body is clean inside. If you remove the throttle body check the inside of the manifold for oil contamination. If there is pooling, clean it out with a clean rag. I hope if you do this you may see some improvement. I expect you have already replaced the spark plugs but if not add this to the list. Its worth starting with stuff like this as its low cost, before moving on. If you have warning lights the cars ECU may comgtain error codes that can lead you to any problems so a diagnostic or check with MES software is a good place to start. Check also that the car is still full of water in case there is a head gasket problem.

 

[Mike1alike]

Yes, it's strange you can't see any stored errors, they usually do store after EML lights up.
Yours sound like a misfire problem and that could be caused by bad coil packs, bad leads or bad plugs.
Take a look on the engine running in the dark, see around the leads if it lights up like the Christmas lights. If it does, the leads are bad.
Do check them all, coils, leads, plugs and maybe get new ones, good quality. See if the guarantee covers it.
Of course, the worse case scenario, the problem could be caused by damaged ECU, but by what you described, ECU should be OK.

 

[puntodeltathema]

Random misfires can be an ECU fault on the 1.2 cars. If you have mail order ECU repair places in your country it would be worth getting your dealer to pay for it to be removed and checked/repaired. (Car might be off the road for a few days).

 

[Mike1alike]

Random misfires can be an ECU fault on the 1.2 cars.

Can be, but when it is it 100% stores an error about it. And it acts a little bit different than @Maryland31 described his does. It sounds to me like his is just bad coil packs. Careful now, running with bad coils does damage the ECU. So get it fixed, sooner!

 

[rmjbn1]

I'm suspicious that EML is triggered but no codes stored?
Doesn't sound right
As Panda Nut above says, I would download MultiECUScan and try again with a decent OBDII interface
Then it should show you which cylinder is misfiring so we can start to diagnose

New timing belt recently? Limp mode at higher speed is common if phonic wheel relearn is not done after timing belt change

 

[The Panda Nut]

I did also change coil pack and leads on our Panda and it ran fine for over 50,000 miles. The coil pack was quite expensive though.