It's about the engine going into a different regime which:
- appears out of the blue , for no reason, no matter if I accelerate or decelerate or I change the gear
- when this different regime starts , a bigger trepidation can be felt in the steering wheel and the gas pedal. Seems that there is no loss of power , or maybe a little. It's like the rythmicity or the cadence of the explosions becomes lower or not constant. It's like a wheel is not well centered. But it is not the case , the front tires are new and the wheels are centered. More ever , I renewed the geometry , so no problems there. The bumpers that keep the engine tied to the body are also ok.
- this regime keeps an aleatory amount of time (may be few seconds , few minutes or even hours)
- the way it disappears is also aleatory , like nothing special happened there before.
When I first noticed this thing (one year ago) , the proportion was 99 % time working well , 1% in trepidation regime.
Now has got to 60% working well and 40% working in trepidation regime.
About a week ago I changed the EGR , the debitmeter and had the ECU's soft rewritten by the authorized people from a Fiat service (in this exact sequence). After each change I experienced the same problem . After some time the engine goes into a strange regime with that different vibration. The people from the service could not tell me exactly what could cause this problem.
Before each of the EGR , Debitmeter and ECU rewriting , the tester was put on , but no injection faults or any other errors were reported, injectors and all other parts seemd to work ok. In total 4 injection tests were made in 4 weeks. Same good results for the injectors.
Some say it might be related to a phase variator ( but this seems to be broken more often on petrol 16 V Stilo versions and causes the vibrations to appear just after the engine is started for few minutes when there is no oil and the friction is made metal on metal.)
Some other say that might be a disk from the camshaft which has a rubber middle which wears out after some time.
Some other say that ECU might be ready to die.
Some other say that there is something wrong in the transmision.
I don't know what to think anymore. If I would have had the money I whould have changed the whole engine piece by piece just to feed my teased curiosity and find out why this happens.
But since I don't have that much money I would realy appreciate if someone who's experienced this same problem could tell me how should be solved or if someone who knows exactly what I'm talking about would come with a briliant ideea.
It seems to me like there is a piece that goes wrong in a certain moment , and after some more time it goes back again where it should be.
Or it's like there is a bug in the ECU's injection program that happens each time some conditions are met (some specific parameters are red from the sensors signals) that makes the injection and explosion timing to go wrong. But this would be harder to debug.
One more thing that I noticed and seemed a bit weird was that right after I changed the debitmeter , when I was accelerating from 2000 rpm to 3000 rpm constantly , at about 2500 rpm I was feeling some kind of kicks in the but sometimes, and othertimes just oposite (loss of power or jerks for fractions of a second) like the engine was strangling but for very short amounts of time.
After the ECU was rewritten , these kicks in the but and hickups almost dissapeared meaning they moved from 2500 to 2000 but are barely noticeable, extremely weak.
Thanks a lot for help.
