[Joda]

Hi!
I have in my garage an Opel Astra-G Diesel, 2002 year.
The problem is if I drive and change the gear,
lift my foot from the accelerator pedal the engine is still on
the same RPM as before for a short time around 10-15sec.

It is really hard to drive with this problem.

No DTC set in the ECU.

I checked with diag tool the accelerator pedal how that is reacting when I lift my foot from it, but it works like a charm.
I also checked the wiring but no fault found...

What I found strange, the h.p. pump have a rpm reading in my diag tool, and
the rpm is still sitting high when I release the accelerator pedal.
Could the problem be in the h.p. pump?

Any idea what could be the reason or what to check?

Tanks
My best regards.

[pankar]

Check if the engine gets air from the hose of the vacuum. For check sprayed with flammable spray to the hoses and the manifold.

[reload3d]

Possibly the MAF/MAP sensor needs replacing, unplug it and try idling the car with it unplugged to see if there's a difference.
If the speedo works better then the sensor will need replacing with a genuine one only, cheap ebay ones don't tend to last long and can confuse the ECU.

If this doesn't work give your throttle body a good clean, could be sticking and causing your issue also.