Technical Rough running but passed MOT emissions...?

[Newboi]

Hi all,

I used to be a regular on here back in the day *cough* 16 years ago *cough*

We now have a 2009 500 1.2; we never had any problems with it until the sump started leaking, and the rear section of the exhaust fell off.

We had both replaced. The EML light came on afterwards, and it turned out the exhaust hadn't been sealed properly, so it was re-sealed, and the EML cleared. Ever since then, it has been running rough at idle. I replaced the throttle body, checked the air filter, replaced the pre-cat O2 sensor, replaced the coils and spark plugs, and replaced the MAP sensor, and it doesn't seem to have improved.

The 500 went in for an MOT last week. The mechanic noted that it was running rough, but it went through the emissions test with flying colours.

So I'm stumped. I haven't looked at any of the fuelling side, i.e. injectors, fuel filter, fuel pump, etc., and haven't replaced the coil pack or post-cat O2 sensor, but surely the rough running would be, at the very least, affecting the emissions or triggering more EML codes?

Any help would be hugely appreciated.

 

[steveras57]

GET a second hand injector rail( only about £50 )after spending 6 months and much money chasing a low speed misfire and lumpy idle doing that cured my issues straight away!

 

[Derbyfella]

Have you checked for errors using MES?

 

[The Panda Nut]

Our Panda 169 69HP breathes a lot of muck from the crankcase breather. It pools in the inlet manifold and causes rough running. I mop it out once or twice a year and it fixes it. The engine runs very smoothly most of the time, I think it messes up the MAP sensor that lives in there, I have reduced the problem by fitting a catch can but it still needs periodic cleaning. This makes it sound awful when it goes off. Its worth a check as this costs nothing.