Technical Panda TwinAir Cold Misfire

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Technical Panda TwinAir Cold Misfire

Andrewkirsanow

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Hi all, new to this forum but I have a problem and you guys seem very knowledgeable and helpful!! I have a 62plate panda twin air which has now done 43000 miles, and recently had its second service. Since then, when started in the morning it has a lack of power and sounds like a misfire. It also sounds a bit 'tappety' like when valve clearances used to get too big. After a minute or so of trying to pull away smoothly, it smoothes out and runs perfectly for the rest of the day. Even if parked up for hours, I come back and it starts and runs fine. When left overnight, it's back to the misfire again. It's now doing my head in. I took it back to the guy who did the service and he confirmed he had used the correct oil grade with fiat and checked plugs etc. The only thing of note, he said, was an unexpectedly high snootiness on the new plug noses. Anyone else had a similar issue?? Or can offer any suggestions?? Thanks in advance!

Andy.
 
Hi,
43K miles.. should be well run in then.., (y)

did he actually re-calibrate the Multiair unit when changing the oil..??,
as that's a SLOW process he may just have skipped,;)

charlie

IF it's still doing it -I would get it into FIAT before the warranty is up..,

charlie - 2013 Punto TA
 
Hi varesecrazy, what do you mean by, ' re-calibrate the Multiair unit when changing the oil?' That's not something I've heard yet.

As for my mileage, it worries me every time I look down and see it creeping upwards!! Especially on a relatively new tech engine!

Thanks for the replies so far guys!!
 
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I haven't experienced any of these symptoms but on any other car I'd say the colour of the exhaust tail pipe shows that it's running too rich.
 
Okay, so. The plot thickens. Today the car started fine as usual and started to misfire as usual. I drove away and did about 1 mile mostly downhill and the miss didn't rectify itself this time. So I pulled over and turned off with the key. Restarted and there was no trace of a misfire. To me,this suggests that the ECU is getting confused about running trim at some stage of the cold start process. Any ideas??

Also, does anyone have any further info on what was mentioned earlier in this thread about an oil change reset or some such??

Cheers
Andy
 
Did you ever find a cure for this? Mine is in at the moment been looked at. As per usual the diagnostic equipment failed to find anything. The Dealer has escalated it up to Fiat UK and got them involved.

Some times it is so bad that you can feel the misfire through the floor pan of the car. I have a video of it that'll upload when I get chance.
 
I've suffered this before, but not on the TA (yet)
From a cold start it popped and missed and continued to run rough/rich.
Until...
I turned the engine off and restart and it ran ok.

Funny, as I seem to recall it started this around the same time of year as now.

Turned out to be the heater element part of the upstream O2 sensor.
Seems it wasn't heating fast enough, though the element wasn't broken.

As the cold engine warms, the fuel trim goes from:
Open Loop, a preset, start me up and warm me up quick, rich fueling set of values.
to
Closed Loop.
Closed Loop uses the up stream O2 to trim the fueling via heat in the exhaust, as the O2 self generates a small electrical charge depending on how hot the exhaust gases are.
So it Switches the fueling back and forth, from lean so the PCM adds more fuel, to rich so it takes fuel away.
This Switch in voltage (between 0.1v and 0.9 volt with the middle line being 0.45v which is perfect fueling) should take less than a second.

To do this quickly from cold start the O2 heats it's self rather than rely on the exhaust gas heating it (eventually) as old EFI did years ago.

A lazy heater element fails to respond quick enough, so when the PCM checks the Switch time in voltage from it against the Engine Coolant Temp Sensor and they do not fail within spec, the fueling trips into Open Loop System Fault and stays there.

So you drive around stuck in Open Loop System Fault which is rich like the Open Loop at cold start, but the exhaust gas have now heated the O2 and it will respond if required.

So now you clear it from the Open Loop System Fault by turning off the engine and restarting the car and Hey Presto, it runs fine again until the coolant and O2 sensor go stone cold again and you start all over again.

To go back to the System fault, it usually needed leaving overnight, but I did time it and got it to repeat after around 4 hours.

It drove me mad for weeks, as the Open Loop System Fault wasn't logged as a DTC, though could be viewed in real time when logging.

This lack of DTC I guessed was fact it only ever happened once every drive cycle (right at the start) and the heater element was complete (but slow) so didn't show as a open circuit fault..

The O2 (I thought) checked out ok, generating the right sort of signals when heated and the heater element resistance was reasonable when bench tested.
I even check the supply to the heater element from the fusebox to connector, all was ok.

By chance (rather than being clever) I pulled the down stream one which was same part, I also had a new one on the shelf.
When checking them on the bench, it became clear the original had a slight resistance difference within the heater element circuit.

To confirm, I tried all three in the Up Stream position.
The original failed again and again (a long process as the car needed all night to cool down) and the other two worked fine every time.
 
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Said very slowly and loudly " DO YOU SPEAK ENGLISH" gestures arms for added effect ;-)

Jesting aside that was a very informative post. Thank you for taking the time to put that together
 
Tell them to look at the UniAir control. Sounds like similar symptoms to my Sisters Alfa MiTo TwinAir, and that turned out to need a new UniAir control, which I imagine serves the same purpose as the MultiAir unit on the 4 cylinder engines and can fail too - albeit more readily than UniAir seems to on the 2 cylinder engines.
 
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