Technical Strange juddering when accelerating normally

[ivanjuaric]

Hi all members,

Croma 200HP 2.4 mjet Symptoms
juddering/struggling when accelerating between 1700 - 2300 rpm (not always)
it is more intensive when the car is under load

When car is cold (first acceleration in the morning)
- Car drives excellent and no juddering/struggling

When MAF sensor disconnected
- NO juddering/struggling when accelerating
- In this case, the EGR is always closed (off)

Hard acceleration
- NO juddering/struggling , car has power and everything is fine

VGT (Turbine solenoid) disconnected
- car has no power, but there is NO juddering/struggling

Driving uphill
- juddering/struggling is more intensive
- Sometimes, I receive warning (ESp, ABS, Hill holder error), but it disappears
- Hill holder, ESP and ABS works normally

Changed parts
Air Flow Meter - New
EGR - New

From my PoV it could be related to auxiliary belt or Alternator?
Does anyone had similar problems?

Thanks

 

[Hellcat]

Probably alternator and/or battery. These cars seem very delicate when it comes to their electrics.

 

[halilson]

My 2.4 had the same symptoms for several months. I disconnected the swirl flaps and fixed them in the open position and it's never happened since!
Took 10 mins. Worth a try, plus it's free

 

[ivanjuaric]

Hi Halilson,

I doubt if it is related to swirl valves, as I cleaned the whole intake manifold and swirl valves 8 months ago.

How to ensure that swirl flaps are fixed in open position? Is there any procedure?

 

[halilson]

I made sure that they were fully open and then cable tied them in place. Eventually I will remove the manifold, remove the flaps permanently and give it a thorough clean.

 

[Doofer]

Have you cleaned the boost sensor (it may go by other names). I can tell when mine needs doing, it needs 2nd instead of 3rd gear on a hill I go up regularly.

 

[JOHN COOPER]

How do you find the the boost sensor.

 

[Doofer]

https://www.fiatforum.com/croma-ii/246118-clean-your-boost-sensor-now.html

I think registration is now required to read the instructions on Vectra-C, but it's quick and free to join and a very good resource for us owners of a Vectra-in-disguise. The instructions are very good - photos and full guide.

 

[halilson]

On the 2.4 it's on the back of the plenum chamber, at the top in the middle. It's held in by one torx bolt. Very easy to get to.

 

[ivanjuaric]

In the meantime I had ESP/ABS Hill holder failure. I changed the wire of rear wheel sensor and the juddering / struggling sound disappeared. It seems that the strange sound was related to ESP / ABS. Will keep you informed.