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Old 31-10-2016   #1
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Question Mis-firing issue

I have a 2011 Punto Evo and am getting mis-firing problems but not all the time, usually when pulling away. It can be fine for weeks/months then starts again which makes it difficult for mechanics to trace. My local garage thought it was the MAP sensor (whatever that is)! They have replaced it twice and I have also taken it to a Fiat garage where they have done a computer upgrade. Now it has started again. I can only liken it to the feeling of the car running out of petrol or like the old days, a faulty plug. Anyone got any ideas? Its driving me nuts!!!
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Last edited by saxman23; 31-10-2016 at 13:19. Reason: Forgot vehicle details
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Old 01-11-2016   #2
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Re: Mis-firing issue

Engine size?
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Old 03-11-2016   #3
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Re: Mis-firing issue

1.4. The issue seems to do it when the engine is cold. As soon as it reaches a hot temperature it runs perfectly!
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Old 03-11-2016   #4
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Re: Mis-firing issue

Multi air?
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Old 03-11-2016   #5
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Re: Mis-firing issue

Yes Punto Evo GP Multiair
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Old 11-11-2016   #6
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Re: Mis-firing issue

Any error codes? How often is car serviced? Oil level low?
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Old 15-11-2016   #7
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Re: Mis-firing issue

Quote Originally Posted by saxman23 View Post
1.4. The issue seems to do it when the engine is cold. As soon as it reaches a hot temperature it runs perfectly!
Inlet manifold gasket (lean condition misfire)? If you have a miss at cold, it is likely something that is expanding when engine warms up. Obviously, a misfire diagnostics is a science of its own, but just a guess ...

What I would do, is read the codes with VAG OBD scanner + multiecuscan software and see if you get p0300 (multiple cylinder misfire) or any of p030x (single cylinder misfire), check the freeze frame data for the code and base the plan of attack on the result.

Another thing: Since it is a MAP engine (correct me if I'm wrong) ... How does it idle? Does it rev high? Is it rough idle? Would be nice to get the fuel trim data (short term [integrator, as they call it] mainly, keeping an eye on long term [Block Learn in FIAT terms]) live on cold idle, so that we can do some meaningful troubleshooting.
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Last edited by igno; 15-11-2016 at 11:31.
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Old 15-11-2016   #8
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Re: Mis-firing issue

Gave it another thought... As you have a new map sensor, I would look at its reading also on cold engine...
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Old 15-11-2016   #9
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Re: Mis-firing issue

Quote Originally Posted by saxman23 View Post
1.4. The issue seems to do it when the engine is cold. As soon as it reaches a hot temperature it runs perfectly!
any news..??
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Old 15-11-2016   #10
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Re: Mis-firing issue

Thank you all for your advice. Unfortunately I haven't a clue what you are all talking about when it comes to diagnostics tests and how to do them ( my first car was a 1953 Ford Prefect!!)
. At the moment the problem seems to have gone away (hopefully). I did pay 50 for a diagnostics test at a Fiat garage and all they did was update software and said it should be ok. Its happened a few times since though!!! So if it persists I suppose I will have to take it back and tell them. Thank you all once again for your help.
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Old 15-11-2016   #11
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Re: Mis-firing issue

hi,

your car uses a Multiair until to actually inject the AIR + FUEL,

when these fail, misfiring is often the 1st symptom,

is your car out of warranty..??

charlie - Oxford
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Old 15-11-2016   #12
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Re: Mis-firing issue

Quote Originally Posted by varesecrazy View Post
hi,

your car uses a Multiair until to actually inject the AIR + FUEL,

when these fail, misfiring is often the 1st symptom,

is your car out of warranty..??

charlie - Oxford
Good point on Multiair. As usually Fiat comes up with something innovative ... electromechanicalhydraulics ... Yes, this one might fail, didn't come to think on that one.

But, if Multiair fails, it should have a performance degradation as well (just a thought)? Fiat is claiming to achieve up to 10% power and even 15% torque numbers increase (just a quick read-up online, I'm no expert on newer Fiat cars) ... Why would it only act on cold (I'm not saying it is impossible, but why ...)

Again, I would check the codes, see live data, etc ... I'm rather sure that VVT failure would affect the emissions and thus lambda readings and thus fuel trims ...
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Old 15-11-2016   #13
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Re: Mis-firing issue

Quote Originally Posted by igno View Post
Good point on Multiair. Why would it only act on cold (I'm not saying it is impossible, but why ...)
cold = higher oil viscosity..?? - (maybe..)

it could be almost anything causing stutters when cold..

as you say - DIAGNOSTICS - are the key
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Old 27-11-2016   #14
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Re: Mis-firing issue

If it's a multiair my money is on the multiair unit itself. I've stripped the multiair unit and found it's weak point and have rectified it. I bought one for the wife a couple of years ago. Before I sorted the multiair unit the car wouldn't even run. She's now done 7,000 miles and it's never missed a beat. The fault I found is definitely something that's been designed to go wrong. I charge 150 for this fix
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