EDIT: The quick takeaway from my P1497 experience is that a failing turbo diverter valve causes additional codes when you have an atmospheric vent spacer, because you end up with a continuous air leak after the MAF. In my case most codes were resolved just by removing the spacer and putting the defective valve back on (at which point I was only getting a code P2885), and all codes were resolved and boost restored by replacing the diverter valve with a new one.

I'm about 3 weeks into ownership of a 2010 Cooper S manual, and just started getting an intermittent code P1497 (Bluedriver translates it to "Downstream Throttle Air Leak") a few days ago, sometimes accompanied by 2B64 and 28AA. Every time the code triggers, the computer pulls power quite a bit, like it's dumping most or all of the boost, and of course I get the half-full engine icon in the display. Weirdly, it seems like the codes do not appear if I leave the A/C compressor on for the whole trip. That leads me to believe, whatever the problem, that the car can only detect it at low throttle openings (A/C compressor requires more than minimum throttle at idle). No obvious misfires and no misfire codes.

After getting the car I changed out the water pump, cross car coolant pipe and thermostat housing (prior one was stuck open, keeping coolant temps below 170 degrees). In the process of getting to the coolant pipe, I moved the intake manifold away from the head for better access. I believe I reconnected everything properly, and have since inspected for obvious issues with my work. I had almost a week of great performance after doing the work before the first P1497 appeared.

Has anyone experienced this kind of intermittent code where a leak is only detected with the A/C off? Any ideas on the source of the issue would be much appreciated.

 

I expect the veteran owners out there will not be surprised to hear that intermittent errors became constant. I also started to get MAF codes (2B51 and 2B5F) codes because the previous owner installed an atmospheric venting spacer on the diverter valve and the diverter valve had failed at the diaphragm (vents to atmosphere all the time in this scenario, so of course the mixture is way off). I resolved all the codes by removing the atmospheric venting spacer and bolting the pieces of the defective diverter valve back on. Boost is obviously low until I get the new diverter valve next week, but at least it's more drivable than it was when constantly losing post-MAF air to the atmosphere.

I'm planning to walnut blast the intake ports this weekend, so hopefully with that and the diverter valve I'll be squared away for a while. Ignoring all the stupidly unreliable plastic components, this is a fun car.

 

I started getting P2885 codes consistently after removing the atmospheric vent spacer and before installing the new diverter valve. With the new diverter valve installed, boost is back and no codes.

Around the same time I walnut blasted the intake valves. The response is improved, but the main difference is a big reduction in vibration at high load/high rpm, presumably because the airflow is much more even across cylinders.

My valves were pretty awful looking. Before, cleaning setup and after pics:



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