1216 TPS code and poor engine operation

[RossfromAZ]

Hey all,

I am experiencing a rough idle, stalling, and what feels like a sort-of rev limiter around 3k under WOT; however, the car *will* redline under lesser throttle application. The car will idle without stalling once warm, although engine performance is still poor.

CEL flashes and will occasionally illuminate solidly, usually at idle.

After performing a stomp test, I pulled code 1216, after which I tested both the TPS and ICV with a DMM per Bently's E36 service manual procedure — both tested within normal limits with one exception, the ICV does not buzz with the key in the ON position.

Also, I did take the car to a German specialist on a whim *before* I began my own troubleshooting (met someone who made it sound like they had a ton of experience with these cars) — he could not figure it out; also, I think he messed with the throttle body limit screw, and I am not sure if that has potentially made the situation worse/more difficult to diagnose.

Any ideas, M42 experts?

*Edit I forgot to mention that the car idles fine upon starting for several seconds, then will begin to die unless the throttle is feathered until it warms-up.

Additionally, car runs *slightly* better if ICV plug is disconnected – will still stall cold though.

Thanks in advance,
Ross

[bmwman91]

What is the Bentley test procedure for the TPS? Pull back the boot and measure voltage across pins 1 & 2 to verify that it varies smoothly as you open the throttle? I think that code 1216 is one of the few Motronic faults which actually corresponds to its description lol. A somewhat common problem is that the wires which go into the connector will fatigue and break right before the crimp in the terminals. Sometimes this happens inside the insulation so you cannot see it, and you can't pick it up by measuring the TPS itself. You would test it by running a continuity test between the plug (unplugged from the TPS) and the ECU connector (unplugged from the ECU).

Wiring diagrams for the engine controls are in section 1360 of the 1991 and 1992 PDFs.

https://www.armchair.mb.ca/~dave/BMW/e30/

If the harness is bad up at the connector:
The connector housing and terminals are all available inexpensively on Digikey, so fixing it is pretty easy if you have basic crimpers for open-barrel terminals.
Housing: https://www.digikey.com/en/products/...7578-1/2054419
Terminals: https://www.digikey.com/en/products/...7771-3/2054475
Basic crimpers (I have used these myself and they work well): https://www.bmotorsports.com/shop/pr...roducts_id/364

If the ICV is not buzzing at all with the key in accessory-II position, then it is either gummed up and stuck, or seized. I would remove it and verify that the little door moves smoothly and without resistance. The easiest way is to just shake / rotate it along its axis. If the door is not gummed up, you will feel/hear it bouncing off of its stop. If it is all gummed up, you can shoot some MAF cleaner or 99% isopropyl alcohol through. Just keep the end with the hose barbs downward so that the solvents do not get into the body. You can also try smacking it with the handle of a screwdriver to see if it starts buzzing...that is also a tried-and-true method lol.