Technical 2011 Twinair missfire cyl 1 only on idle and when warm

[dan1979]

Bought a 2011 TA that has missfire on cyl 1 only , and this only happens when i have driven the car for a while(you can drive the car without any problems for as long as youlike but when stopping and let it idle for 10 sec it loses cyl 1 , Mil is on and only get 2 DTC P0301 and P0300 (missfire cyl 1 and random missfire) , changed following coils,sparkplugs, upper+ lower oxygen sensor,camshaft sensor,map sensor, fuel pressure regulator,crankshaft sensor, injectors , ground under battery is checked and good but nothing helps,as soon as a part has been changed i have done replacement in autocom for that part.
Got new oil+ filter + the mini filter is checked and ok

I can see that it gets to much fule on idle when warm thats why cyl 1 dies , but if i rev it it starts up again and works until it idles again
idel is 850 rpm
It got spark (took of the coil and placed a sparkplug in it and it works but as to much fule goes in it cant ignite it.

I have autocom and what i can see the map sensor is reading 900mbar on idle and atmosfere pressure is 1000mbar so its only have 0.1 vacuum to pull the fuel regulator and i think that is to low?

Any ideas?

Tested leak with smog mashine but there is no trace at all ?

Have no more ides what i can do???

only has 120000km

 

[jrkitching]

Hello and welcome to the forum

That's the right sort of mileage and symptoms for a failing uniair module, but you'd need positive confirmation before spending the sort of money replacing it would involve.

There are a few relevant threads on this forum - I'll try and pick one or two out for you.

Meanwhile, have a read of this.

Update: read this thread and follow the links in it.

If it does turn out to be the uniair module, there's a guide in the guides section of this forum describing how to replace it.

 

[dan1979]

Thx i have done compression test and its about 12-13 bars on each cylinder, it can be the multiair module but as the car goes so good cold as warm all the time exept on idle, if idle would be 1400rpm it would not missfire at all, and what i have seen is that if i worm the car up buy reving the car there is hardly any missfire at all on idle wehn warm but if i drive the car to ots warm and thn let it idle it stops firing on cyl one all the time
It can be the multiair module but i most exclude everything else before i change that , i can test the acctors with autocom and both sides sounds exactly the same

Im more curius if 0.1- 0.15 bar is normal intake vacuum at idle on the twinair?shows up as 850-900mbar reading at map sensor

 

[jrkitching]

It can be the multiair module but i most exclude everything else before i change that

I'd agree with that. You need to be as certain as possible that this is the cause of the issue before spending this sort of money. It's definitely not something you'd do on a hunch.

I don't think a subtle uniair fault will show on a simple static compression test. Have another read of Mark Stammer's article. That shows how difficult it was to actually make the diagnosis - and that kind of test equipment isn't available to most garages, much less to home mechanics. One thing he did say was that he noticed a subjective difference between the cylinders when deliberately disabling one and running on the other - perhaps this is something you could try?

As far as I know, there's no simple way of ruling out a faulty uniair module in cases like this, and that's something that would be very useful to have. Please keep posting and let us know how you are getting on - this could help a lot of other folks.

 

[dan1979]

Does anyone know what vacuum the car should have at idle in the intake manifold?

 

[Tropicalmike]

what twin air engine do you have ? I have access to both an 85 and a 105 PS Fiat 500 twin air ( euro 6 ) and can hook up my MES to get you my value,

You can read my threads about my diagnosis trail when I had 1 cyl misfire and thinking about a worn Uniair

 

[dan1979]

Many Thx for that mine is a 85 2011 twinair, i will read the threds about the trail also, i have changed the injector also

 

[dan1979]

Cant find the thred about the diagnoise trail , can you show the link?

 

[Tropicalmike]

Cant find the thred about the diagnoise trail , can you show the link?

Hi,

I will try and get you the vacuum reading tomorrow.

Try this link, not sure how much will be relevant

Twin Air misfire after oil change ? | FIAT 500 (2007+)

I have just carried out an oil and filter change on a 64 plate twin air 105 at 35000 miles. We have had the car for 7 months. I have now had a couple of issues with a misfire and engine warning light coming on and the Start-stop unavailable showing . However , the first 3 journeys of about...

www.fiatforum.com

 

[jrkitching]

@Tropicalmike

Thanks - it's hugely relevant.

There's very little real knowledge out there about how to definitively diagnose uniair faults on the 0.9TA. Given the costs and complexity of its replacement, this is badly needed. Changing one isn't a job anyone would want to do on a hunch.

As far as I know, you're the only person on the forum who's successfully identified that this was the cause of their running problems without access to specialist test equipment that even most garages won't have.

You've also successfully replaced one yourself, and written a guide about it.

You're the forum's resident expert on this!

 

[jackwhoo]

Hi,

Does anyone know what vacuum the car should have at idle in the intake manifold?

Does the intake manifold have any vacuum ? I thought twin air doesn't have a throttle plate because the air flow is controlled by the unfair module.

 

[jrkitching]

Does the intake manifold have any vacuum ?

Look at the intake manifold pressure graphs in Mark Stammer's article.

There is a clear difference in the intake pressure peaks between the cylinders when running with the faulty uniair module installed.

This would certainly help to pinpoint the fault.

You'll need a sufficiently responsive pressure transducer and an oscilloscope to see this, though.

 

[jackwhoo]

@jrkitching Thank you for linking that article - very interesting.

 

[jackwhoo]

Im more curius if 0.1- 0.15 bar is normal intake vacuum at idle on the twinair?shows up as 850-900mbar reading at map sensor
[/QUOTE]


Map sensor reads atmospheric pressure engine not running so around 1000mbar .

You read intake vacuum at idle as -100 to -150mbar but that reading is relative to atmospheric pressure.

1000mbar minus 100mbar = 900mbar
Looks correct to me.

If the twin air has no throttle body then any inlet manifold vacuum with be very low only caused by the air filter and inlet air tubing, non running turbo

 

[Tropicalmike]

This sounds correct about the MAP sensor ( Boost Pressure). I hooked up my MES today and took a screenshot for Dan1979 as below. With hindsight I should have perhaps taken another shot with the atmospheric reading that is further down. I will do it again when I have chance ( It is my wife's car ) It is quite high atmospheric pressure today it may have been around 1035 mBar . The Car was almost a full operating temp and idle speed was normal at 820 . So it looks like the vacuum I have at idle is very small , almost zero .



Based on what Dan1979 has replaced to eliminate the problem ( just about everything ) If you then assume the uniair is misbehaving. When the engine is up to temperature and the issue only occurs at idle revs . So in my case when I had a misfire it occurred with a cold engine and the actuator on cyl 1 was sticky . This issue is with a hot engine. So at idle revs you don't need much fuel and air . if the inlet valves are staying open too long due to the uniair actuator being worn on cylinder one at idle would this show as increased vacuum at MAP ?? or is it a case that the actuator is a bit sticky on cylinder1 and is not opening enough for that small amount required at idle and thus not enough air with correct fuel giving the misfire. The actuator coils have a milli amp signal, when the signal is small for minimal opening this is when the wear means the actuator does not reach the correct position.
As soon as you demand higher speed the uniair actuator is getting a much bigger signal and opening more and the problem goes away. The wear in the actuator is just in the part/range mostly used at idle. That is a theory , just trying to think of a way to prove it.

What happens is if you are driving at say 3000 rpms and you just take your foot of the gas and let the car decelerate with the engine as a brake. Does the misfire show then or only once you have the clutch down and no gas?

What grade oil is used ? I think yours is a Euro5 engine and 2011 is one of the earlier twin airs so 5W40 ? might be worth using 0W30 C2 and see if it has any effect. If you read my thread about using the higher viscosity oil that revealed cyl 1 sticking when cold . the actuator test from MES or your Autocom probably gives the full milliamp signal to the actuator so you hear the "ticking" and it is fully open . But in real running at idle that signal is going to be small for the minimal opening . The signal and actuator opening is modified when the oil is cold and also the the idle rpm is higher when cold so probably the worn area is not used.

Even at idle 820 rpm or 13,6 revs per second each actuator is operating 6,8 times per second. That is a lot of movement for 120,000 kms of driving and perhaps it may not have had the best condition/correct oil for it's entire working life . It is precision machining in the actuator variable solenoid valve and it is may be showing signs of wear. Have you seen the attached description on multiair/uniair ?

 

[Tropicalmike]

@Tropicalmike

Thanks - it's hugely relevant.

There's very little real knowledge out there about how to definitively diagnose uniair faults on the 0.9TA. Given the costs and complexity of its replacement, this is badly needed. Changing one isn't a job anyone would want to do on a hunch.

As far as I know, you're the only person on the forum who's successfully identified that this was the cause of their running problems without access to specialist test equipment that even most garages won't have.

You've also successfully replaced one yourself, and written a guide about it.

You're the forum's resident expert on this!

Thanks for the complement, though "resident expert" is bit OTT . more a case of "in the land of the blind the one eyed man is king!"

 

[Tropicalmike]

This sounds correct about the MAP sensor ( Boost Pressure). I hooked up my MES today and took a screenshot for Dan1979 as below. With hindsight I should have perhaps taken another shot with the atmospheric reading that is further down. I will do it again when I have chance ( It is my wife's car ) It is quite high atmospheric pressure today it may have been around 1035 mBar . The Car was almost a full operating temp and idle speed was normal at 820 . So it looks like the vacuum I have at idle is very small , almost zero .

View attachment 454938

Based on what Dan1979 has replaced to eliminate the problem ( just about everything ) If you then assume the uniair is misbehaving. When the engine is up to temperature and the issue only occurs at idle revs . So in my case when I had a misfire it occurred with a cold engine and the actuator on cyl 1 was sticky . This issue is with a hot engine. So at idle revs you don't need much fuel and air . if the inlet valves are staying open too long due to the uniair actuator being worn on cylinder one at idle would this show as increased vacuum at MAP ?? or is it a case that the actuator is a bit sticky on cylinder1 and is not opening enough for that small amount required at idle and thus not enough air with correct fuel giving the misfire. The actuator coils have a milli amp signal, when the signal is small for minimal opening this is when the wear means the actuator does not reach the correct position.
As soon as you demand higher speed the uniair actuator is getting a much bigger signal and opening more and the problem goes away. The wear in the actuator is just in the part/range mostly used at idle. That is a theory , just trying to think of a way to prove it.

What happens is if you are driving at say 3000 rpms and you just take your foot of the gas and let the car decelerate with the engine as a brake. Does the misfire show then or only once you have the clutch down and no gas?

What grade oil is used ? I think yours is a Euro5 engine and 2011 is one of the earlier twin airs so 5W40 ? might be worth using 0W30 C2 and see if it has any effect. If you read my thread about using the higher viscosity oil that revealed cyl 1 sticking when cold . the actuator test from MES or your Autocom probably gives the full milliamp signal to the actuator so you hear the "ticking" and it is fully open . But in real running at idle that signal is going to be small for the minimal opening . The signal and actuator opening is modified when the oil is cold and also the the idle rpm is higher when cold so probably the worn area is not used.

Even at idle 820 rpm or 13,6 revs per second each actuator is operating 6,8 times per second. That is a lot of movement for 120,000 kms of driving and perhaps it may not have had the best condition/correct oil for it's entire working life . It is precision machining in the actuator variable solenoid valve and it is may be showing signs of wear. Have you seen the attached description on multiair/uniair ?

I checked on my MES again today , at idle of 823 rpm, engine up to temp
atmospheric 1037 and boost also 1037 mBar so no vacuum at idle . So does this mean for dan1979 that his turbo is not delivering enough at idle or is there an air leak between turbo and inlet? Or is it the Uniair for cylinder1 opening the inlet too much/too long or too little causing increased vacuum? also attached is another description on Uniair . I admit I am struggling to get me head around all of it !

 

[A3jeroen]

On idle there will hardly be any pressure from the turbo. I would expect a vacuumleak in the intake.

gr J

 

[Tropicalmike]

Dan1979 says he has around 100-150 mBar vacuum on map sensor so where is the extra vacuum from if not the induction strokes from the cylinders pulling it. So too much inlet valve opening from a worn Uniair solenoid on no.1 cyl. at idle ??? If there was an air leak somewhere between turbo and inlet i think that would show up at higher revs and load but Dan says engine Ok then .

 

[jackwhoo]

Interestingly on first screen shot post 17 there is a 144mbar difference between boost pressure and intake pressure.

I don't think looking at gross inlet vacuum is going to help on an engine with no throttle plate. It appears that graphing the pulses from the map sensor can show an issue between cylinders. As per article in post 4.