Fun with P1140 / P0505

[keptech]

This code seems to be one of the more over asked questions but I figured I'd ask if anyone is feeling charitable. Worst case, once I do figure it out I'll summarize it here.

When I picked up my latest ti ('98/M44) it had a stuck open thermostat -- since I corrected that and did a cooling rebuild it seems like it's been a whack a mole of correcting vacuum leaks (potentially of my own doing from the DIY) and malfunctioning emissions components where I'm not sure where to place the blame yet.

It initially ran so bad I had a shop check it out and address vacuum leaks and issues with the CVV/DISA valve. I was left with an occasional surging idle that was attributed to the Idle Control Valve. I cleaned it with no change and ended up replacing it. Replacing the ICV has left me with a "bouncing" idle (from 1000-1500 RPM) at stop/rolling that has turned into a full on bouncing all the time at idle.

I narrowed the behavior down yesterday -- If I just start it and leave it sitting, the car starts perfectly, idles great, and warms up to closed loop/full temperature without a problem, idling around 1000 RPM. But if I even blip the throttle the idle will continually bounce up and down between 1000 and 1500 RPM indefinitely and I get the P1140 and P0505.

At this point I'm thinking throttle position sensor, the throttle cable itself, or something with the alternator or electrical system. Has anyone seen anything like this? Readings are attached.

[keptech]

I did some tests on the throttle position sensor and it seemed OK, but I replaced it anyway as it was cheap enough. No effect.

Rather than keep replacing potentially related sensors, I decided to have an expert check it out again -- it turns out that the new Bosch idle control valve I had installed was a dud. The shop ordered up and installed another new ICV and it runs like a top now.

This was the first time I've had a decently expensive part be a dud out of the box. :P

[BlackBMWs]

Ya, New ICV not cheap. Glad you got it sorted, and thanks for posting the results. I'll sort through my knock sensor pre-test codes this weekend. i'm hoping it's simply a loose connector.