Hello all...

Christ it seems like a long time since I've been on here, forgot my password and never got round to getting a new one.. anyway...

I'm having a rather major problem with my coupe at present, I'm beginning to think it may well be on its last legs!

When I start the car from cold (left overnight or over 5 hours) the car runs perfectly, pulls like a car with 240hp should! Also, I can drive it for hours and its still fine.

However, if I start the car when its warm (started any time after 20 mins of leaving it up until its cold again) the engine management light comes on and doesnt go off, my AFR gauge shows it running in LEAN even when under load and the car runs quite literally like a bag of sh*t! Misfiring would be one term I'd use although it sounds like its not firing on all cylinders?! if revved past 3k and allowed to settle it pop's and bang's very loudly out of the exhaust and although it sounds quite cool I'm pretty sure its over/underfueling like crazy.

I've got absolutely no idea what it could be as if it was terminal it would be like it all the time and not just when its warm!

I'm a bit limited by time and money at present as looking to move out so hopefully someone may have a clue what it is, FF hasn't ever let me down yet

Regards,

Dan

Quite possibly coil pack(s). When they're on the way out heat can affect them and their performance will drop with heatsoak, causing a weak spark and rough running.

Would that bring the Engine management light on though? Thansk for the reply!

Skate2create said:

Would that bring the Engine management light on though? Thansk for the reply!

Click to expand...

If it's causing a misfire or not igniting the fuel properly, yes.

Last possibly blindingly stupid question (I think I already have the answer but better to clarify it):

With what you're saying, the (may be more than 1) coilpacks are not functioning properly and giving power to the plugs to cause the spark which is leading to unburnt fuel entering the exhaust, the lambda sensor is seeing this excess fuel and leaning off the fuel mix to compensate. This is why my AFR gauge is showing the mixture to be very lean (unless I change gear which causes it to briefly flick into rich mix but then that is due to the coupe adding extra fuel to compensate for the recirculated air when the throttle is backed off...

Correct?

Of course I have had a shandy at lunch, I may be talking utter tosh, I hope not!

Dan

Yes, that's exactly right.

If the a coil pack is failing, it won't give enough current/voltage to make a good spark. This means that the mixture won't burn properly, giving a misfire, rough running, loss of power, etc.

Yes, as you said, the lambda will read that there is too much oxygen in the exhaust (I think it's that way round.) and that there's too much unburnt fuel, so it will lower the short-term fuel trim accordingly to compensate. (Which is why your gauge is showing lean.) Too much unburnt fuel will cause damage the the cat converter and the cylinder wall/liners (If it has liners.) and the rings.

The reason it shows rich during changes is both from the closed throttle and because as you put the clutch in there's no load on the engine.

What colour is the engine warning light? If it's red or flashing, that's usually the misfire warning. I don't know about Fiats, but in many cars when there's a bad misfire the engine warning light goes red and flashes. If that's the case with your car DO NOT drive it as you can cause serious damage.

If you go into the Punto subforum and find the thread titled something like "Diag for a laptop and a tenner" in the last few days it has the info on free Fiat diag software with a OBD-II/CAN cable off eBay. It should help you pinpoint the problem.