Technical Car starts from cold great but as soon as it hits 60c and revs drop it gets a misfire on no 1 and sometimes 1 + 2.

[T140v]

Hi all, first post hope you can help.
I am trying to sort out the lumpy engine on my grandsons car, its a Punto Evo multiair turbo 2010 plate.
It starts from cold no problem and has no error codes or lumpy running until it hits 60c and the revs drop to around 800rpm.
It then throws up P0301 P0300 P0302 misfires in 1 & 2 never 3 or 4. So I have
Moved coilpack 4 to no1 and vica versa, same result as above.
Removed the coilpack from no1 when it says misfiring to check for a spark, good blue spark.
Changed spark plugs, same result, starts from cold and runs perfectly untill 60c then misfires.
Removed the injector rail, manually opened each injector with 12v connector and injected carb cleaner through each injector, all showing a good even fan spray.
Swapped no4 injector to no 1, refitted the injector rail and tried again from a cold engine started fine running like a sewing machine until engine got to 60c and tickover dropped to around 800 then code P0301 code P0300 P0302 back again with misfire 1 & 2 and lumpy tickover, have checked all over for leaks cleaned MAF sensor and Map sensor made no difference .
I have sent for a fuel pressure regulator valve to see if that improves things but I am running out of Ideas.
Any help greatly appreciated and thanks in advance.
Regards Stuart

 

[Pugglt Auld Jock]

Been thinking about this and as noone else has replied I thought I would. I'm not really familiar with the multiair engine but very happy with the N/A FIRE engines. Not knowing your actual car can I presume we have an engine with good compression on all cylinders? That said my first thought is that it'll be running open loop on the internal fuel map stored in the ECU when started from cold. Then, once there's some heat in it it'll switch to closed loop and bring in the MAP and upstream Oxygen sensor which will modify the fueling and this seems to may be where your problems kick in? have you tried pulling the plug to the MAP when it's misfiring? That would make it revert to the stored values so if it runs differently you'd know that would be worth investigating. Didn't know your's has a MAF - our wee ones don't - but you could try pulling it too and seeing what happens. Of course this will set codes but you seem to have a reader/scanner so you can cancel them. By the way, what diagnostic gear do you have? There seem to be people on here who have reported problems with cheaper kit giving wrong codes. I've got Multiecuscan and would recommend it. If you can graph the O2 sensor output you might find something interesting (upstream of course - the downstream sensor doesn't really affect fueling). I'm a big fan of graphing sensor outputs when trying to diagnose elusive faults. Of course misfiring and poor running at idle/low revs which goes away at higher revs is always a prime candidate for suspecting an inlet tract air leak.

Probably none of that helps, but I hope it may stir something in your mind that I've not thought off?

 

[varesecrazy]

Hi Stuart

It could still be a multiair problem

Are you within driving distance of Winchester, Hants ?

There is a specialist there who has A LOT of expertise

Charlie

 

[T140v]

Been thinking about this and as noone else has replied I thought I would. I'm not really familiar with the multiair engine but very happy with the N/A FIRE engines. Not knowing your actual car can I presume we have an engine with good compression on all cylinders? That said my first thought is that it'll be running open loop on the internal fuel map stored in the ECU when started from cold. Then, once there's some heat in it it'll switch to closed loop and bring in the MAP and upstream Oxygen sensor which will modify the fueling and this seems to may be where your problems kick in? have you tried pulling the plug to the MAP when it's misfiring? That would make it revert to the stored values so if it runs differently you'd know that would be worth investigating. Didn't know your's has a MAF - our wee ones don't - but you could try pulling it too and seeing what happens. Of course this will set codes but you seem to have a reader/scanner so you can cancel them. By the way, what diagnostic gear do you have? There seem to be people on here who have reported problems with cheaper kit giving wrong codes. I've got Multiecuscan and would recommend it. If you can graph the O2 sensor output you might find something interesting (upstream of course - the downstream sensor doesn't really affect fueling). I'm a big fan of graphing sensor outputs when trying to diagnose elusive faults. Of course misfiring and poor running at idle/low revs which goes away at higher revs is always a prime candidate for suspecting an inlet tract air leak.

Probably none of that helps, but I hope it may stir something in your mind that I've not thought off?

Thanks for your reply Jock, I will be doing a compression test tomorrow also looking at the PCV valve and I had thought there must be a default program to run up from cold then change over when up to temp so I will certainly look a pulling the plugs on the sensors to see if it will revert to open loop, I'll check out the upstream O2 sensor as well. I have bluetooth OBD2 dongle that I connect to a free fault reader but it does show graphs of fuel trim oxygen sensors and a list of sensors. The misfire does not go away as the revs increase one the car has warmed up.
Thanks

 

[T140v]

Hi Stuart

It could still be a multiair problem

Are you within driving distance of Winchester, Hants ?

There is a specialist there who has A LOT of expertise

Charlie

Thanks for the reply Charlie, I'm in Doncaster and I would not like to drive it out of the street at the moment, had a look at that multiair system on youtube there's a lot going on in that cylinder head. On a very steep learning curve comp test and other bits to test again tomorrow.
Regards Stuart

 

[Mike1alike]

I'd say that the problem is with the air intake manifold's gaskets and I mean especially the ones between the manifold and Cylinder head. They are worn out and need replacement and probably the ones from cylinders 1 and 2 are having more cracks/wear. They don't seal properly anymore and on high air humidity, when the engine warms up, the humidity from the air that gets in (and shouldn't) condenses and therefore the misfire.
I've seen threads about this problem (that sometimes gives no errors) and lots of people replaced electrical components with no effect. I've seen it being discribed as "The Fiat curse" by folks that didn't fix it and were very satisfied with their Fiat cars until this problem occured. I've had this on my Punto and fixed it by replacing those gaskets. I've posted about it on the Punto mk2 thread as well.

 

[varesecrazy]

Compressiontests are misleading on these.. :-(

 

[Pugglt Auld Jock]

Compressiontests are misleading on these.. :-(

? Because of the multiair unit's way of working? I'd not thought of that.

 

[T140v]

I'd say that the problem is with the air intake manifold's gaskets and I mean especially the ones between the manifold and Cylinder head. They are worn out and need replacement and probably the ones from cylinders 1 and 2 are having more cracks/wear. They don't seal properly anymore and on high air humidity, when the engine warms up, the humidity from the air that gets in (and shouldn't) condenses and therefore the misfire.
I've seen threads about this problem (that sometimes gives no errors) and lots of people replaced electrical components with no effect. I've seen it being discribed as "The Fiat curse" by folks that didn't fix it and were very satisfied with their Fiat cars until this problem occured. I've had this on my Punto and fixed it by replacing those gaskets. I've posted about it on the Punto mk2 thread as well.

I have unplugged the Map sensor and the boost sensor the car now runs on 4 cylinders, I have checked for inlet manifold leaks by spraying the area with carb cleaner there were no increase in revs. Just going to talk to an auto electrician about the MAP sensors.

 

[Mike1alike]

I think that if it would be the MAP sensor's fault, you wouldn't have misfire only on cylinders 1 an 2. Spraying carb cleaner test doesn't always work, especially when there are very small cracks.

 

[Mike1alike]

And or course, yours being multiair, that is a possible cause, if the valves on cylinders 1 and 2 are not working right. But I'm guessing that if something would be wrong there, there should be a monitoring system and you would get a specific error for it. Anyway, you shoul check it to be sure it works fine, but if it does and the problem is still there, take into consideration the replacement of those gasekets. And even more so, if they haven't been replaced untill now. Because gaskets do wear and needs to be changed.
And a little detail, my Punto is 2006 and I had this problem about 4 years ago. I'd say that after 12 years of use is not too soon to take into consideration replacing gaskets.