BAYEMVAY
08-19-2004, 11:23 AM
This is my first post, so before I get started, I would like to thank everyone who posted such useful information. I've saved hundreds of dollars in repair costs and hours of time using advice I found on this board.
As for the hunting idle problem, my '89 525i (M20) surges a bit while idling. To verify the ICV, I disconnected the 3-pin ICV connector while the car was idling. The idle speed should increase to about 2000 RPM's. My result - No increase in RPM's. Thoroughly cleaned the ICV with throttle body cleaner and verified it's ability to rotate freely. Verified the resistance measurement between outside contacts (pins 1-3) @ 40 ohms. Verified the resistance between center and outside contacts (pins 1-2 & 2-3) @ 20 ohms, +/-10%. I verified the battery voltage present at pin 2. However, the voltage between 1-2 and 2-3 should each measure about 10V. Between 1-2 I get 9.5V. Between 2-3 only 4.5V. When I remove the ICV completely, the RPM's jump to 2000 RPM's. If the disconnected ICV is supposed to cause the same 2000 RPM condition, I believe the ICV defaults to the 'wide-open' condition. Perhaps there is a spring inside that holds the valve 'open' when no voltages are present. I don't believe mine does that. I hope I'm wrong, especially at $150 ICV replacement cost. Can anyone confirm this?
Somehow, the wrong voltage at pin 2-3 still bothered me, and then I noticed that phildg2000 had the same symptom in one of his recent posts concerning an idle problem. His later found a bad throttle position senser. When he took care of his TPS, he was able to get the stomp test routine to work. Another thing my '89 won't do. So the TPS is on my to-do list. I'll let you all know how it goes. One of the things I want to find out is if the TPS repair affected the ICV voltages (I'm just trying NOT to discover a bad ICV). But even if it doesn't, I'll take a working stomp test!
As for the hunting idle problem, my '89 525i (M20) surges a bit while idling. To verify the ICV, I disconnected the 3-pin ICV connector while the car was idling. The idle speed should increase to about 2000 RPM's. My result - No increase in RPM's. Thoroughly cleaned the ICV with throttle body cleaner and verified it's ability to rotate freely. Verified the resistance measurement between outside contacts (pins 1-3) @ 40 ohms. Verified the resistance between center and outside contacts (pins 1-2 & 2-3) @ 20 ohms, +/-10%. I verified the battery voltage present at pin 2. However, the voltage between 1-2 and 2-3 should each measure about 10V. Between 1-2 I get 9.5V. Between 2-3 only 4.5V. When I remove the ICV completely, the RPM's jump to 2000 RPM's. If the disconnected ICV is supposed to cause the same 2000 RPM condition, I believe the ICV defaults to the 'wide-open' condition. Perhaps there is a spring inside that holds the valve 'open' when no voltages are present. I don't believe mine does that. I hope I'm wrong, especially at $150 ICV replacement cost. Can anyone confirm this?
Somehow, the wrong voltage at pin 2-3 still bothered me, and then I noticed that phildg2000 had the same symptom in one of his recent posts concerning an idle problem. His later found a bad throttle position senser. When he took care of his TPS, he was able to get the stomp test routine to work. Another thing my '89 won't do. So the TPS is on my to-do list. I'll let you all know how it goes. One of the things I want to find out is if the TPS repair affected the ICV voltages (I'm just trying NOT to discover a bad ICV). But even if it doesn't, I'll take a working stomp test!