Technical 500C Cult Petrol 2015 misfiring and start stop fail

[Bezzy]

Hello,

Took my car for MOT and service. Full service oil change spark plugs etc. afterwards started misfiring when cold and when accelerating intermittently. Been happening for about 3 months. No fault codes, no dash lights, no overheating, no other indicators until start stop failed the other day, into limp mode, start stop unavailable message. Stopped car, restarted, still misfiring but message gone. Car is definitely less juddery without start stop on but still not right. Took back to garage can’t find anything, all plugs checked. Drove 250 Mile round trip no issues except the intermittent misfiring on acceleration. Any clues??? Thanks in advance

 

[John202020]

Ignore stop start altogether.
Started misfiring after servicing think that's the first starting point go to a trusted mechanic explaining what's happening don't leave the issue probably a simple issue note you need Fiat specific software on a pc to read the codes.

 

[Bezzy]

Ignore stop start altogether.
Started misfiring after servicing think that's the first starting point go to a trusted mechanic explaining what's happening don't leave the issue probably a simple issue note you need Fiat specific software on a pc to read the codes.

Thanks for the advice, can you (or do you know anyone who can) recommend a good Fiat mechanic in Nottm?

 

[John202020]

Sorry I'm "up north" but other members should be along

 

[AndyRKett]

It’s extremely unlikely there would be no error codes given the limp mode cutting.

Misfiring is usually accompanied by a flashing engine warning light do you have this ?

I’d suggest the current garage are giving you the runaround and don’t want to take responsibility for whatever the cause is

 

[Ralf S.]

If they changed the plugs they might have yanked the HT caps off by pulling on the cables rather than the caps, and that might have damaged one.

If the coils are good and sending volts to the HT caps, then I'm not sure whether you would get an error code if one of the caps is not able to pass the joy on to the spark plug. There's nothing "not working" as far as the ECU is concerned. But... if your "S/S unavailable" is lit, then there must be an error code, so try to read the codes when the error is showing.


Ralf S.