XM 2.0i RFZ staggering idle

[teuski]

I have a '90 XM 2.0i with the 89kW RFZ engine.

It is the version with MAP sensor in ECU and no MAF.

The problem is, that when the ignition is on but the car is not running the fuel pump, pump relay, fuel rail pressure regulator and canister purge electrovalve (the latter one, there are two) all make a ticking sound all the time. So the pump is running and making pressure in the rail and does not stop.

Possibly related to this the engine returns slowly to idle after revving. With high RPM it runs fine, but when i lift the throttle it goes down to around 2500rpm and then drops with little steps to normal idle. After that it runs ok on around 1100rpm but throttle response is not so good, it staggers a little if i floor the throttle.

I have the engine bay connectors and earth spots. I assume the ICV is working and when i block it (it is of the type that sticks to the intake manifold and is attached to the air inlet via a hose) the engine stalls.
If i detach the MAP sensor hose and suck it hard it affects the engine running so the MAP has to be at least somewhat alive.

Any ideas?

[teuski]

Well the ICV is bad, idles better with it disconnected.

Still rhere is the problem with the fuel pump control. Even with the relsy out the purge valve knocks. I'm i on the right track suspecting it's the ECU?

[teuski]

Turns out it was all due to a bad ECU. I got a spare one yesterday and all my woes went away. Even the idle is now good.
Before that i had diagnosed that it was the control ground from ecu for the fuel pump relay etc. that was cutting out.