julianfoulger

When I had a similar problem to you, there were NO fault codes, and most sensors, including the IACV and the TPS, were replaced including the leads - but no difference. It took several weeks for me to get the right idle screw adjustment to get the car in equilibrium.

In the end, to ensure that the butterfly valve was shut and that I was adjusting from 0 degrees, I adjusted the idle crew so that it was clear the valve was shut. I then worked from there adjusting the screw in small increments until I hit 26 steps.

I assume you have replaced the faulty coolant sensor (the one feeding the ECU). Replacing the IACV is an option on the basis you have cleaned it but not operating right (not the cheapest of sensors) and perhaps if you still have the old TPS put that back in and see if this makes the difference.

I fully understand the frustration that you are going through. I spent a fortune on sensors and I ended up messing around with the idle screw and going on short test rides for several weeks before I got it right.

I learned to follow the data/evidence but the lack of any fault data being during this period made the whole episode even more frustrating. The problem is that the fault data is based on whether the ECU is getting data from sensor X and but the ECU is not smart to check whether the data is accurate.