Help with M42 running issues

[Greg Mierz Mtechnic]

I recently installed a head on a 91 318is m42, Did the chain guides also. Car was brought to me on trailer. Now with everything together, it will start but not respond to the throttle properly or idle. All air hoses were replaced are seem tight. I can find no obvious air leak. The stomp test says 1215 or airflow meter. Tried another one no difference. The TPS switch seems ok, it has variable resistor as the throttle moves. The funny thing is when I disconnect the tps switch and start the car, it pegs to redline and the key must be turned to stop it. I am at a loss with this. Tomorrow I'll go back over everything again and see if I missed any thing. Any ideas?? The crank and cam sensors must be ok as it starts ok but won't react to the pedal at all, won't hold a steady rpm anywhere.

[DesktopDave]

I thnk you're definitely on the right track with the AFM or TPS.  That's odd that a TPS would redline, unless maybe the connector on the AFM is full of water or has a broken wire.

I had a 1215 code too.  I did three things that fixed it, but I'm not sure which did the trick:
I patched a big vac leak on the ICV pipe under the manifold.
I pulled an odd little plug/extension out of the AFM harness.  It was a BMW fix that changes the resistance of the AFM for smoother running.  That plug wasn't waterproof & it likely shorted the AFM sensor readings.
I cleaned the AFM flap with some throttle body cleaner & lubed it with some light machine oil.

Once I did all that the codes went away and it runs much better now.