Technical Fiat Grande Punto 1.3 engine shaking/juddering

[jackwhoo]

Hi guys,

My 1.4 8V 2013 is shaking on operational temp at idle (700rpm, VVT, Euro5). When I turn A/C , rpms are going up to 720 and theres no shaking. I feel shaking of whole car on hot idle, in steering wheel, seats, everywhere. I opened bonet on idle and watched engine movement when I quickly press gas pedal, engine shaked once "forward and then back". Also when I quickly accelerate for example on 3rd gear, it shakes with car, and when I release gas pedal, it shakes again.
So based on this quickly method it looks like dogbone engine mount has broken rubber.
I didnt eye inspection yet, just to want your opinions/experiences.
What I saw on pictures, this dogbone is made by 2 parts? One looks like "triangle" with some rubber bushings, and 2nd part is dogbone itself...is that correct please?
Or how to simply diagnose if main engine mount is bad, or lower (dogbone) is bad? My main mount has space between upper metal part and rubber part approximately 1,5cm. Is it ok? I'd like to diagnose it before creeping under car to dismaount dogbone...so any info is helpful here guys! Thx ;-)
I changed dogbone on 2 previous cars, but on one car there was also shifter movement back and forth, and on 2nd car I heard metal bang, so it was easy to identify bad dogbone...
Maybe I can shake engine via oil pan back and forth, and see movement around dogbone...this looks to me like easiest method...?

Hi rado,

I wouldn't be concerned with the slight vibration you have. From your description it sounds like 700rpm is the resonant frequency of some parts of your engine, that would explain why such a small increase in revs causes it to go away.

Dog bone mount if cheap just replace it, then you will know.



Good luck
Jack

 

[jackwhoo]

mechanic said the drive shafts looked fine. spent already 600£ on all this but havn't changed the driveshafts yet. so this might be the last resort.

I don't feel like spending anymore money on the car.

Hi,

With the best will in the world , drive shafts have to be really very bad before it is possible to detect faults in them by manipulating them by hand with vehicle elevated.

Good luck
Jack

 

[Rado77]

Hi rado,

I wouldn't be concerned with the slight vibration you have. From your description it sounds like 700rpm is the resonant frequency of some parts of your engine, that would explain why such a small increase in revs causes it to go away.

Dog bone mount if cheap just replace it, then you will know.



Good luck
Jack

Hi Jack. You are right, when engine is not fully on operational temperature, there is no vibration. I dont know if Fiat lowered idle rpm to 700, maybe because of Euro 5 limits. By diag is hot idle oscilating between 696 to 704. My problem will be solved if I could change idle rpms via diagnostics to 710 or 720 But there is also one big shake when I press gas pedal quickly and then another shake when I release pedal and engine goes back to idle rpm. Ok, I'll check that dogbone, shake with enginw through oil pan and it should be clear

 

[GrandePunto PL]

That was my suspicion too - 700 rpm is too low for 8V petrol engines to run perfectly, smoothly.
There is an irregular shaking sometimes (and yes, using A/C smooths this out completely, because rpm raise).
In the past, most of the FIRE family engines had 750-1000 rpm idle! Below that was rare.
Why they lowered it, I don't know (because VVT, Euro4 or what?)...

It can not be changed easily (via FES/MES) - it probably requires ECU hacking, programming (like tuners do), chip-tuning. Maybe "Examiner" is able to do it(?).

 

[Rado77]

Thanks for info ;-) Yes I think it's low because of Euro5 (+VVT). I shaked engine through oil pan, but I didnt move the engine even 1mm So dogbone should be good. Now Im thinking about main mount, here are some pictures of it. I dont know if its ok, or if its too low for example...I mean the 1cm gap between rubber and metal, I can put there my finger! Is it normal please?

 

[jackwhoo]

Thanks for info ;-) Yes I think it's low because of Euro5 (+VVT). I shaked engine through oil pan, but I didnt move the engine even 1mm So dogbone should be good. Now Im thinking about main mount, here are some pictures of it. I dont know if its ok, or if its too low for example...I mean the 1cm gap between rubber and metal, I can put there my finger! Is it normal please?

Yes normal
The gap is so engine doesn't transmit all it's vibrations to car body.
With out gaps you would feel lots more vibration.
Don't worry so much about vibration and engine idle , think of it as a reminder to turn off your engine rather than sit with it running at idle for long periods

 

[Rado77]

Thx for info! I though that my gap can be so big and engine is "sitting" on chasis. I'm going to refill A/C and then I'll using A/C always ON (automatic A/C). Now almost all filling is away, compressor is turning On OK, but I hear sssssssss from ventilation and theres no cooling effect. So filling A/C will solve this idle shaking issue

 

[Rado77]

So aircon full, no shaking at idle Price 85Euro including ozone desinfection. Circuit was completely empty, strange that ECU allowed compressor to turn on when pressure sensor must detect no pressure in the system...They also checked leaks with light and glasses but no leak found. They said that sometimes radiator has very small damage somewhere which cannot be detected visualy. So I will see...

 

[DGPunto]

They should have put a marker in the gas. That will leave a coloured mark where it leaks

 

[AdrianVasiloiu]

done this and around 1200-1300 revs an unusual shake is happening. So i keep it steady at this interval and it's doing it constantly. When going over these number of revs , everything seems fine

Exactly the same problem on 1.3 multijet Punto Evo. Have you managed to repair it?