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Old 30-06-2017   #1
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900cc Twinair rough start from cold

We have a 2013 Fiat 500 0.9 Twinair, 20k miles that runs rough from cold.

When plugged in the only code we are given is misfire on cylinder 2, have changed plugs and coil packs, but still runs rich for a minute or so from a cold start. Have flushed engine and changed the oil 5w 40 as I am told they are fussy about the oil grade.

Some mornings it seems fine other mornings it runs rough from cold as if it is over fueling?

Any one have any idea where to go next?
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Old 30-06-2017   #2
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Re: 900cc Twinair rough start from cold

Hi and welcome

What are you using to read the codes? MultiECUScan can read all the Fiat specific codes, as well as carry out resets, etc. A lot of basic readers can only read generic codes.

I've not got any personal experience yet with TA engines (we pick up my wifes tomorrow), but I'd probably start by looking for split pipes, and then test the MAP sensor (assuming the TA has one!).
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Old 30-06-2017   #3
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Re: 900cc Twinair rough start from cold

Quote Quote:
Any one have any idea where to go next?
It's only cylinder no2 that has a misfire?

If you ran the car for a few miles to get the engine thoroughly warmed up and then checked for error codes...?

I'm not familiar with your car but I would guess that it is multi point injection .. an injector per cylinder?

It's just a thought, but at start up if the injector is lazy and 'sticky' that may cause your misfire. Or it may be an electrical connection to that injector.

It sounds as though the problem is fuel/air mix to cylinder no2. If a sensor was at fault it would cause problems across all cylinders. Initially I thought that a sticking/dirty air idle valve may be the culprit - but again, that would cause problems across all cylinders.

Do the easy things first - try a can of injector cleaner in the petrol tank and take the car for a good, hard long blast. It isn't often injectors fail in the true sense of the word, but they can become a bit lazy due to either corrosion or a build up of 'gum'.

I doubt very much whether your car has any valve trouble as you haven't done enough miles..
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Old 01-07-2017   #4
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Our 11 twin suffered from this..
And I changed oil and filter twice.

Also put new plugs and coil packs on.

I then revved it's nuts of from cold and has been loads. Better.

Have you cleared code and checked since.
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Old 04-07-2017   #5
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Re: 900cc Twinair rough start from cold

I would not rev any engine hard from cold
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Old 07-07-2017   #6
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Re: 900cc Twinair rough start from cold

Quote Originally Posted by Putput100 View Post
We have a 2013 Fiat 500 0.9 Twinair, 20k miles that runs rough from cold.

When plugged in the only code we are given is misfire on cylinder 2, have changed plugs and coil packs, but still runs rich for a minute or so from a cold start. Have flushed engine and changed the oil 5w 40 as I am told they are fussy about the oil grade.

Some mornings it seems fine other mornings it runs rough from cold as if it is over fueling?

Any one have any idea where to go next?
This is a 4 year old car with only 20K miles. Does it do lots of short journeys?

Get it warm and give it some Italian tuning.

D
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Old 05-08-2017   #7
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Re: 900cc Twinair rough start from cold

Hi

Our 2012 Panda Twinair has developed the exact same problem. All following an oil change and a Multiair 'oil change' reset on Multiecuscan..
See Pic 1

Now, from a cold start (takes about 6+ hours from parking up this summer), the engine runs very rough and if allowed to idle, a misfire will develop that Multiecuscan identifies as from cylinder 2. I've swapped plugs and coils and this problem stays at cylinder 2. I suspect that the mixture is being set so rich by the ECU that it is wetting the plugs, particularly no 2 to such a degree that it cant spark, and misfires. This is detected by the system and Limp mode is sometimes engaged.

This seems to be connected with the Multiair learning process as on subsequent cold starts, the rough running is appearing to lessen.

Allowing the engine to warm up slightly, restarting the engine the misfire clears and the car can be driven normally and tickover is smooth. I seem to remember this happening to a lesser degree at the last oil change but cleared up after the first cold start or so.

I am suspecting a failure of the No1 Lambda sensor is a culprit in all of this. At the cars last MOT back in March, the tester had difficulty in passing the vehicles emission test on Lambda reading, (HC and CO were fine though). Fuel economy has never been great but the vehicle is mainly used for short journeys.

A scan on Multiecuscan shows no reading at all for Lambda1 signal (just a 'V') but other figures related to it are there.

See Pic 2

Is this confirming my suspicion of a duff Pre-Cat sensor or is this just a bug in the software?!

I'm also feeling I should forget the Multiair reset on subsequent oil changes, it being more trouble than it's worth
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Last edited by Vic20; 05-08-2017 at 18:26.
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Old 05-08-2017   #8
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Re: 900cc Twinair rough start from cold

Unplug the front lambda and see what happens and compare the reading's ?
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Old 06-08-2017   #9
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@Vic20

If its smoother with the factory infill figure ( missing lambda input ) you will have your answer.

Charlie 2012 ta
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Old 06-08-2017   #10
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Re: 900cc Twinair rough start from cold

Thanks folks, yes, unplugged Lambda and started from cold, reasonably smooth . ECUScan givas a 'Lambda resistance' DTC as expected.

Reconnected the Lambda while the engine was still running and after about 5 seconds the misfire on cylinder 2 started with the engine jumping around (still surprised how well it runs on 1 actually ). Disconnected the Lambda and everything smoothed out after 4-5 seconds. Took her out for a gentle drive with the sensor off (check engine light on) and all was ok, a quick check on the economy seemed to indicate that had improved too.

Measured the heater resistance on the sensor which I think is Blue and Yellow wires and that reads at 3 Ohms. NGK seem to indicate it should be 30 ohms so maybe a short to earth there.

Anyway, a new sensor is on order (NGK 90532). Will report back.

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Old 10-08-2017   #11
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Re: 900cc Twinair rough start from cold

New Lambda sensor fitted yesterday. All rough running on cold start is gone and fuel economy has improved markedly.

I'm suspecting this Lambda sensor hasn't been right for a few years now, you never know maybe even the Stop-Start will start working again after 4 years

Multicuscan still doesn't show a reading for Sensor 1 though. The one reading that would have probably helped all along! It also always shows the battery voltage as 0.56v I've never liked this buggy software much over much superior products availble for other makes of car and the customer support is woesome. I am using the registered version 3.1 which is over a year old but I'm damned if I'm upgrading for another 50 for a bug fix!
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