Strange engine stutter

[Omez]

Hi,

Im hoping for some bright minds that can explain my engine problems.
It runs all fine most of the time, but a few times now lately the engine has been acting up.

When driving in 1-3 and applying minimum trottle the engine accellerate/deacellerate quite rapidly causing a jerking motion. I tested it out a little more today and revving the engine it revs all fine up to 1800 rpm, there it makes somewhat strange sound that I havent quite identified. Im not shure how to describe it, if it sounds like one sylinder not firing or what, but it is too even for not only one sylinder not firing (allmost like every other sylinder is off)

If i continue to rev the engine it starts to shift between 1800-2000 rpm's quite rapidly (2000-1800-2000 in little under a second or so). As i keep applying throttle this shifting in rpm speeds up until it stops and the engine revs up to about 4500-5000 rpm.
At this rev the engine seems to work properly. If I reduce the throttle a little it goes right back to shifting between 1800-2000 rpms (I can't get it to stay at for excample 3000 rpms)

Under load the engine works perfectly and I havent noticed any lack of power when driving. I have checked the fuel filter without any luck. And the fakt that it works normaly under heavier load it doesnt seem to be the fuel pump.

Spark plugs is going to be changed again to be sure but they was changed last year so shouldnt be it.

Could it be bad injectors?
Any tips appriciated.

[evildky]

step 1. check the ecu for codes
step 2, verify the car is idling on all 6 cylinders