This could be an airleak after the airflow meter, any let breathe dragged in here isn t seen by the ECU and suitably not compensated for and can thin the engine out and can as a consequence allow the engine to rev occurring subsequent to not desired causing scratchy running. As its a mechanical deformity it tends not to direction on the deformity buoyant and you can sometimes hear a hissing noise taking into account the engine running.
Thanks for your response. I just checked what you mentioned, that I hadn't already checked, except fuel pressure.Let me tell you a tiny more nearly the pain history. It currently has a master tech credited idle let breathe manage valve and tps installed. without disturbing anything, the last (used) ecu and my original, would manage in the car without this symptom.
I don't have any check engine lights unless I unplug the MAF sensor. in the same way as the MAF is plugged in then the car will stall unless I put my foot on the accelerator. There is then an intermittent popping solid coming at idle.