I've had two 1984 318s, and I've suffered many problems with the EFI, particularly idle quality.. too fast of an idle, and/or poor running in general.


I've gotten it running pretty well, and I'd like to share what I've learned, and I hope it can help someone rescue and perhaps enjoy one of these older E30s much more quickly than I have been able to.


Having done hours of searching and reading, I've come to the conclusion that since these cars were only made in this configuration for a few years, there is little information, and it appears that people give up on the cars, or make major changes, which might not be requried or justified.


The particular car that I recently purchased has been extraordinarily difficult to get running properly, requiring replacement of every component of the fuel system. The car sat for more than 20 years, and had apparently been "worked on" by some less than knowledgable mechanics over the years. So this project was frought with separating faulty work from faulty components.


Once I got it running reasonably well, I was stuck with a car that idled at 1600 RPMS no matter what. The ICV that belongs to the car was long missing, and the correct one isn't available. The correct module for the early cars is near impossible to find, so another solution was required.


What I ended up settling on was using an auxiliary air valve from an earlier BMW with CIS injection. These devices are thermostatic, and electrically heated not unlike an electric choke that would be used on a carburetor.


Utilizing the AAV required modifying the valve body, and the throttle position switch. I removed and cleaned the throttle body. Removing the throttle stop screw is not easy. At least mine wasn't. It's not supposed to ever be adjusted (oh well). I removed the tiny threaded screw, and replaced it with a philips screw that had a jam nut. After chasing the threads, this allowed me to make adjustments by hand as long as the jam nut was left loose. The next problem is that the throttle position switch doesn't have the requried adjustment to deal with the slightly open throttle. It still needs to signal the fuel control ECU at idle and WOT in order for the fuel cuttoff to work, off idle enrichment, and WOT enrichment. I cut the slots in the switch as required to get the switch closed at idle, once I figured out where idle was.


The AAV simply bypasses the throttle. It can be installed in place of the original ICV. This way when it's open, the air is properly metered by the airflow meter, and fuel delivery is correct. When the AAV is closed, there is no airflow through it at all, to the point that vacuum will collapse the hose. Without the throttle body modification, idle speed would be too low, or non-existent.


I used one of the valve cover nuts to secure the AAV, and it's grounded at that point. Power is sourced at the coil. In the coming weeks, I will install a relay for the AAV, which will only provide power with the oil pressure switch closed- this way the heater in the AAV won't be active unless the engine is running.


What I now have is an engine that starts at 1700-1800 RPMs, and as the AAV warms up ( about 3-4 minutes) the idle settles down to around 850-900 RPMs. Additional air will be required to boost idle for A/C.. and I will work on that soon.
https://youtube.com/shorts/J5Y5vUPOrek?feature=share
AAV1.jpgAAV2.jpgAAV3.jpg