A couple of months has passed since I fixed my Volvo's idle and stalling problem and I have been using and enjoying the car for fault driving duties.
But the other day the check engine light came on and VIDA reports error codes ECM-640A and ECM-640F - both indicating a fault with the variable valve timing system.
VIDA suggests that the problem could be sure to the timing belt slipping a tooth, or dirty or incorrect oil causing a restriction in the camshaft reset (VVT) valve. The VIDA page also links without explanation to the crankshaft sensor page which is concerning.
Most reports of the same problem, including the generic error code P0011, suggest that cleaning the VVT valve is of no help and that problem usually lies with the actual camshaft gear.
It's a bit suspicious that the wrong oil is a possibility and I very recently changed the oil.
It's also suspicious that the VIDA error code diagnosis page references the crankshaft sensor, which has already been a problematic area for me.
I'm not sure how I'm going to fix this problem. I will do the easy and free options of check the resistance of the VVT valve and cleaning it, but I'm not hopeful.
I already checked timing, and to the best of my skills it looks like it is correct. I have also read that these engines are unlikely to just skip one tooth.
I need to replace the timing belt so I could change the gear at the same time although that will add several hundred dollars to the job and I understand that it requires special tools.
I could change the oil again, to see if that helps.
I am not really happy with those options because I prefer to be confident that something will solve the problem rather than guessing and throwing parts at the issue in the hope that it will help.
For the moment the car is running okay. Cold starts are not right and I expect the car will be using more fuel and probably lacking power, but it is driveable.