AFM reading dodgy at idle, boost creeps up
got the turbo rebuilt last month and shes running alright but the AFM seems to be throwing wonky signals at idle. boost just creeps up to about 0.8 bar when it should sit at zero, and the ECU can't seem to dial it back properly. ive checked all the vac lines, cleaned the AFM sensor with carby cleaner, and swapped in a known good intake tube. reckon its the AFM itself going dodgy or could the ECU be struggling to read it properly?
The AFM itself is your problem here. I sourced a couple of genuine Bosch units from a wrecker in Adelaide last year for $120 each, and I've still got one sitting in the shed. They're not expensive to replace compared to chasing ghosts through the ECU. The sensor gets dirty or the flap mechanism sticks slightly and the ECU reads it as rich at idle, which causes that creep. Swap it out and you'll sort it.
AFM gets flakey when theyre getting on. Mine was doing the exact same creep at idle. Chucked in a used one from a wrecker for 60 bucks and sorted it out. Might be worth trying before you start looking at ECU stuff.
had the exact same thing on mine after a rebuild. swapped the AFM for a spare and it sorted itself... reckon the sensor gets cooked during turbo work if theres heat soak. grab one off the wreckers for forty bucks, way cheaper than guessing.
Had something similar after my turbo work last year; turned out the AFM was just dirty despite cleaning it. Took it to a specialist who recalibrated the whole system and it sorted itself out. Worth checking if your ECU needs a proper reset after the rebuild.