Technical Intermittent misfire - no codes

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Technical Intermittent misfire - no codes

frazersx

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Hello All,

I have had an intermittent single cylinder misfire for around 300 miles now and have gone through certain procedures to try and get it running correctly again. The model is the 1.4 MultiAir Turbo 135.

The warranty expired a year ago and the car has now done 41000 miles, it was registered in 2013, it has not been serviced through a FIAT dealership but the correct parts and correct grade of oil have been used as per the handbook.

The misfire occurs when the car is hot and it generally (but not only) appears when you stay above the speed of 50-60MPH for any length of time, it can also appear at low revs in higher gears but less predictably, the misfire disappears when you shift down or pull over and let it idle for a moment, it never misfires on idle & there are no warning lights or codes when it does it !

So far I have changed all the spark plugs and tested each coil - the problem is still occuring, interestingly we actually unplugged a coil whilst the car was running - a warning light came on, when the car was restarted we plugged it back in and there was no historic fault code on there.

Has anybody had this problem? or have any advice? anything would be appreciated as we don't really know what to do with it next, I don't want to take it to my local dealership as they have already charged 85 to diagnose the issue and achieved nothing in two working days.

Frazer
 
Hi ! - I'm still none the wiser with this problem, had a few different garages offer to look at it but they cannot advise on what process of elimination they are going to go down (I dont want them to duplicate work)

Rather ominously when I went to see my parents today and outside another 62 plate 135 Punto was being pulled onto the tow truck for complete engine failure, they had extended warranty though so they'll be fine

Frazer
 
Had the parameters reset today - I will let you know if this works !
 
Okay it wasn't that.. Still doing it ! The start stop unavailable message came on though with a yellow triangle
 
Okay so the throttle is lumpy, car sounds like it's on its way out, when we unplugged the solenoids whilst it was running ,it didn't throw up a fault so through a process of elimination and reading the Alfa & FIAT forums we have come to the conclusion that the multi air unit is to blame (the actuator) it is going to set me back £850 GBP - I'll let you know if that works!!
 
Okay so the throttle is lumpy, car sounds like it's on its way out, when we unplugged the solenoids whilst it was running ,it didn't throw up a fault so through a process of elimination and reading the Alfa & FIAT forums we have come to the conclusion that the multi air unit is to blame (the actuator) it is going to set me back £850 GBP - I'll let you know if that works!!


Shop4parts..and the forum discount..could halve that.

Where are you based..might be worth a trip to burrowsdeano
 
Sounds to me like you have the common multiair failure. I've now thoroughly tested my fix for these and if it's the common problem you would be looking at £150 all done. Is the misfire/ rough running constant now?
 
hi both - thanks for coming back ! do you know how to obtain the forum discount on shop4parts? also - £150 sounds attractive but how is this magic possible? haha - the misfire isn't constant but it is certainly getting worse, especially when warm
 
I'm not sure how you get that discount. As for how it's possible to do the repair for £150, fiat supply no spare parts for the multiair unit and the part that fails has a built in gasket that deteriorates and then starts to loose pressure to the unit. I had gaskets specifically made for the job and have fitted a number of them now. I bought one evo that would not even start. My Mrs then covered 6000 miles with no problems at all. We've since sold that one and she's in another one now which also had a misfire up till fitting my gasket
 
Hi guys

just to update you on this - the mechanic I am using (who has been brilliant!! in contrast to the FIAT main dealership people) is going to try the following - if it fails I may give you a call burrowsdeano

he said 'they didn't tighten/use a thread locking compound on the unit and after time it becomes loose - if the unit isn't too badly damage it will simply be a case of a thread lock and re-torque to specified setting'

I'll let you know if this works, its happening Saturday
 
it works fine now ! drove from ashford to heathrow and back on saturday, gasket was resealed - fiat had used silicone which had all fallen apart, the oil strainer was filthy and clogged, will let you know if this has definitely fixed it but our mechanic has saved us lots of money . thanks for all your help - I imagines burrowsdeano would have done something similar here.
 
Hi, where are you, who's your mechanic? I have a friend with a similar problem.
 
Hello Marcos - the mechanic is in Ashford, Kent - what model & year is the car? what mileage is on it?
 
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