Technical 500 twinair stalls when engine not up to temperature

[timmys]

Hi everyone, I'm new to this forum. Just wished it was under slightly different circumstances that im writing my first thread.

I have a 500 twinaitr - ace car, I love it.. however, after having it 6 months of owning it second hand, 46000 miles it started to develop an issue. when the car is started from cold - it starts everytime, but if I drive anywhere before the engine temperature guage has turned from blue to at least 2 white bars it will struggle when I put the clutch down when approaching a junction or to change down gears, stall and not restart until ive put the car through 6 or seven starting cycles.
I had a mechanic look at it who found no faults on diagnotics. He changed the engine temp sensor but no change to the faulty.
I changed the spark plugs and this fixed the problem for around 3-4 months. I have done this 3 times now, each time its ok for a couple of months then the problem is back.
The plugs come out with a fair amount of carbon on them. more than I would expect for a 2 month old spark plug.
does anyone have any ideas????

Thank you

 

[Al D]

Welcome to the Forum. Sorry about circumstances. Has mechanic changed the coils too, was a recall on early cars.

See this thread. Lambda sensor?!
https://www.fiatforum.com/500/451649-900cc-twinair-rough-start-cold.html
Goudrons and typecastboy have bit more mechanical knowledge than me. Can you advise please Gents?

 

[typecastboy]

I would say Lambda or coil pack too. Not familiar with the coil pack on the twinair but cheap enough to get a used one I imagine although but not so many around.

 

[Al D]

Slight deal on coils. Would mechanic change them just labour to rule them out from one of his suppliers and then return ones he's got in?! Half an hour labour maybe.

https://www.shop4parts.co.uk/?name=...erm=Fiat_500_0.9_Turbo_TwinAir_Ignition_Coils

 

[Goudrons]

I've read something similar that was down to a fault with the butterfly motor in the throttle body.

I believe there's no idle bypass, so the electronics control the butterfly to control idle speed.
There's no physical link, it's all fly by wire, so if it can't position the butterfly properly, it'll likely die when you slow down and dip the clutch.

The reason this doesn't throw a code or MIL is because the throttle position sensor isn't reading outside it's perimeters, it's used to seeing the throttle between closed (1) and wide open (5), so if it's anywhere between at the wrong time, it just can't tell.
You'd only get a throttle position related code if the circuit was shorted or open (broken).


I believe the fix was to strip it down and clean out the gears from the motor to the spindle.
This was on an Italian site somewhere (in Italian).
I think I might have linked to it in the past, I'll see if I can find it.


I reckon the sooty plugs is from the excess cranking and it over fueling as it detects the throttle is open.

 

[John202020]

The sooty plugs ? Not sure more than normal cranking would cause "that much" tends to suggest wrong mixture for some reason, of which there's many, but wrong mixture is also a cause of stalling?

 

[Al D]

If changing the plugs solves the problem in short term still, in your shoes I'd have plugs again and run on Super Unleaded. My Panda TA 4x4 prefers it, runs and goes a lot better. One benefit appears to be a lot smoother restart in traffic with the stop start on. Unlikely to be miracle cure but that's what I'd do.

 

[timmys]

Update.... having a good poke around under the bonnet. I found the oil was low, just below minimum but the oil warning light had not even flickered. I’m going to give it an oil change, oil filter in a couple of weeks as it’s been 12 months. Could very low oil cause it too stall if there is not enough pressure? I topped it up yesterday and had no stalling on way home last might from work, or the cold start this morning at 6am..

 

[varesecrazy]

Are you using the correct oil?

Something is making it overfuel.. assuming you have got a clean airfilter..

If new plugs gives a short fix I doubt it is a coil pack issue.

Idea : what were the MOT emissions results : all recorded readings please

Charlie

 

[Al D]

As car due service, is it due MOT as well. As the readings on that should give a hint to the cause. And a chance to rule out the lambda sensor maybe and clean anything else needed.

 

[timmys]

Are you using the correct oil?

Something is making it overfuel.. assuming you have got a clean airfilter..

If new plugs gives a short fix I doubt it is a coil pack issue.

Idea : what were the MOT emissions results : all recorded readings please

Charlie

Here’s the mot readings... it hasn’t stalled since being full of oil though... ???