L200 K74 Diesel 2.5 O2 Plate.

No engine light on. Very lumpy idle after a few minutes...plus black/grey emmisions.

We suspected Suction Control valve, removed and tested on bench. Solonoid worked perfectly and valve opened and closed, no blockage, filters clean.
Tested operation down to 5V and it still operated.

In the car the supply to the valve was showing 8V on first click of ignition but the valve buzzed and it did not operate.

So the question is what supplies the valve with the signal to open and what voltage should we expect. Is it direct from the ECU or does it have a relay?

Thanks Andrew

Part2 We fitted the valve but did not connect the wiring harness to see if the cars idle would continue to fail or throw up the engine warning light.. To our surprise the car ran perfectly at idle, and reved normally, the idle control was very stable and the automatic valve on the top of the engine was very stable and not cutting in as it had been? It clearly is a fuel related issue that we are having and a suction control valve that is perhaps operating when it should not....any thoughts much appreciated.

Didn't think Classics had a SCV
Thought they only came in on the 2006> B40 DID engine

Good point Nick. I didn't even read this post before cos I thought it was refering to newer models. @Andrew and Mutley . Post a pic up and we'll tell you what it is (EGR or throttle body probably)

This is a SCV for a B40 2.5 DID

See Pic below