BMW E28: ICV Cleaning and Replacing Hose and Oil Change

Not sure how this car ran so decently with all the worn out and dirty bits in the engine... but that's German engineering for ya.

[@rodrigoandrescepedaperez7877]

Hello dear friend. By chance you have the vehicle manual where it specifies the tests that can be carried out in the ICV. I'm having idle instability issues on my 1990 e30 320i. I came across a magazine article that said between the center pin (+) of the ICV connector and ground, you need to measure the battery voltage. And between the center pin (2) and pins 1 and 3, it should measure 10 VDC. In my case, pin 2 and pin 3 measure 4.1 VDC. I measured it at the output of the ECU (positive battery and pin 4 ECU) and the value is the same. I changed the ECU and the output voltage value between positive battery and pin 4 ECU is 4.1 VDC. Some help ?. Greetings from Chile, South America.

[@b.ba.bakana]

Hey Rodrigo, I am not sure I can really help you but I have a Bentley manual and this is what it says: -With engine running, disconnect IAC electrical connector and idle should increase to about 2,000 RPM. -If it does not change, then: 1. Turn engine off and unplug the electrical connector from IAC 2. Using ohmmeter, check the resistance on the two outer terminals of the IAC. There should be about 40ohms of resistance. Check the resistance on the center and outside terminals and they should both be at 20 ohms. *If this test fails on any of the resistance tests, then you should replace the IAC. 4. If the IAC passes the tests, then check the voltage at the connector. 5. Put ignition key ON, turn off any accessories, and there should be battery voltage at the center terminal. There should be about 10 volts at the center and outer terminals. *If there is no voltage reading, then you need to have the IAC or ECU diagnosed by service shop (this is what the Bentley manual says). In any case, just make sure all vacuum lines have been checked, air filter and MAF/AFM are clean, fuel lines are not old, spark plugs are good, etc. The normal stuff. I did have an old E28 that had a weird idle problem that would happen every so often and I found out the ignition was just old and the contacts were worn out. After replacing the ignition it never had the idle/stalling issue. But I doubt that is your case. Good luck!

[@rodrigoandrescepedaperez7877]

@@b.ba.bakana Thank you very much for your prompt reply. I did everything you described and I had read so in the vehicle manual. My problem is that in one of the ECU outputs to ICV, I have 4.1 VDC ... in the other I have 9.8 VDC (close to the 10 you were telling me). I tried 3 ECU's and it is impossible that 3 are bad. I measured the ICV terminals and the Ohmic references are fine. Greetings again.

[@b.ba.bakana]

@@rodrigoandrescepedaperez7877 Then it looks like it could just be related to the wiring of that specific terminal that is at 4.1. You might need to follow the wire and see if it’s shorted anywhere or something. Also, you can just try a replacement IAC, and if that doesn’t work, the problem may just be in another area.