Idle at 1100 rpms
Thread Starter
Burning Brakes
Joined: Dec 2008
Posts: 800
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From: Colorado Springs, CO
Idle at 1100 rpms
In the [Another] idle problem thread I said that my idle was running at ~1100 rpms and some said that it was too high.
So I started looking around and I checked out some of the recommendations I've read in other threads. One was the cruise control cable. I checked it and didn't see anything out of the ordinary. Next I checked the full throttle switch at terminals 3 & 18 and it was as described in the Bentley (continuity with throttle open, and no continuity in all others).
Next I checked the Idle position switch electrically on terminals 42 and 44. I should get continuity with the throttle open about 1mm. I get an open in all positions. To double check I did the switch harness and connector test. Started the engine and let it idle (1100 rpms). Disconnected the idle switch connector and the engine speed is supposed to jump ~500 rpms, it remained at 1100.
So now is pointing to the ECM. Does this sound correct to you?
So I started looking around and I checked out some of the recommendations I've read in other threads. One was the cruise control cable. I checked it and didn't see anything out of the ordinary. Next I checked the full throttle switch at terminals 3 & 18 and it was as described in the Bentley (continuity with throttle open, and no continuity in all others).
Next I checked the Idle position switch electrically on terminals 42 and 44. I should get continuity with the throttle open about 1mm. I get an open in all positions. To double check I did the switch harness and connector test. Started the engine and let it idle (1100 rpms). Disconnected the idle switch connector and the engine speed is supposed to jump ~500 rpms, it remained at 1100.
So now is pointing to the ECM. Does this sound correct to you?
Thread Starter
Burning Brakes
Joined: Dec 2008
Posts: 800
Likes: 2
From: Colorado Springs, CO
Rusnak,
I checked the full throttle switch (is this the same as the closed throttle switch you're referring to above) at terminals 3 & 18 and it was as described in the Bentley (continuity with throttle open, and no continuity in all others).
The idle position switch didn't check out according to the procedure in the Bentley Manual.
The Bentley manual tells me to check the ECV next, except that I can't take the seat off because the previous owner stripped one of the bolts. I need to get that bolt out before I get to troubleshoot the ECV.
I checked the full throttle switch (is this the same as the closed throttle switch you're referring to above) at terminals 3 & 18 and it was as described in the Bentley (continuity with throttle open, and no continuity in all others).
The idle position switch didn't check out according to the procedure in the Bentley Manual.
The Bentley manual tells me to check the ECV next, except that I can't take the seat off because the previous owner stripped one of the bolts. I need to get that bolt out before I get to troubleshoot the ECV.
I haddah Google dat
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From: Fresno, CA
Jorge,
I am going off of memory now (Bentley manual is at home), but the closed throttle switch should be on the left hand side of the throttle. There is a lever that is connected to both the cruise control cable and the throttle shaft. At closed throttle, there should be a microswitch in a little retangular box that opens when the throttle is fully closed. You should hear it "click" when the throttle is opened about a millimeter or so of travel. Bentley should have a procedure to check it's operation and adjustment of the throttle switch.
Next, there is a procedure to set the idle, but you have to disable the ICV first.
I am going off of memory now (Bentley manual is at home), but the closed throttle switch should be on the left hand side of the throttle. There is a lever that is connected to both the cruise control cable and the throttle shaft. At closed throttle, there should be a microswitch in a little retangular box that opens when the throttle is fully closed. You should hear it "click" when the throttle is opened about a millimeter or so of travel. Bentley should have a procedure to check it's operation and adjustment of the throttle switch.
Next, there is a procedure to set the idle, but you have to disable the ICV first.
Last edited by rusnak; Mar 5, 2010 at 12:05 AM.
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Awesome diagram, rusnak! Thanks.
There is a thread on PP about hunting idle when cold and nobody could bottom-line the procedure like you have.
I've got hunting idle (850 - 1200) bounce when cold and suspect it's the ISV. I will check the base idle and then proceed to refurb the ICV. Hopefully that will fix the issue.
Thanks again
There is a thread on PP about hunting idle when cold and nobody could bottom-line the procedure like you have.
I've got hunting idle (850 - 1200) bounce when cold and suspect it's the ISV. I will check the base idle and then proceed to refurb the ICV. Hopefully that will fix the issue.
Thanks again
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I haddah Google dat
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From: Fresno, CA
you need to verify that the dme is in idle mode first. Doug is correct. Put your hand on the icv, make sure it's buzzing. If not, then either the idle switch is bad, not adjusted, or there is an icm issue. ICMs do not go out frequently. I'd check the idle position switch, adjustment next, then harness on the engine [clean and check voltage]. But start with switch adjustment.
Thread Starter
Burning Brakes
Joined: Dec 2008
Posts: 800
Likes: 2
From: Colorado Springs, CO
No joy on the ICV. I feel the vibration from the engine but no buzzing.
Bentley says to check the switch, which I did Saturday and it didn't check out.
I also checked the idle position switch. I should be able to hear a click from the microswitch. I feel something after 1 mm of travel and I can hear something but it is not as I expected.
I also need to check the wiring to the ECM.
As a side note, I'm in Colorado Springs around 6500 ft. so I think I better check the altitude sensor too.
Bentley says to check the switch, which I did Saturday and it didn't check out.
I also checked the idle position switch. I should be able to hear a click from the microswitch. I feel something after 1 mm of travel and I can hear something but it is not as I expected.
I also need to check the wiring to the ECM.
As a side note, I'm in Colorado Springs around 6500 ft. so I think I better check the altitude sensor too.
I haddah Google dat
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From: Fresno, CA
The fact that the ICV is not buzzing is a major clue. I think you're on to something. If there is no voltage to the ICV, then the computer probably doesn't know that the throttle is closed, which is why the rpm is so high. Pull the DME connection to the ICV after removing the spring clip with a small screwdriver or dental pick. Is there voltage to the ICV (key on, engine off)?
The function of the idle position switch is to disrupt power to the ICV as soon as the throttle is opened. It has to be adjusted before you can test it electronically. Check the adjustment first, in other words. Then check the switch again as per the Bentley manual. The microswitch could also be faulty or really dirty. Maybe it's stuck? Yeah, the wiring could be bad too, as well as the ECM.
The function of the idle position switch is to disrupt power to the ICV as soon as the throttle is opened. It has to be adjusted before you can test it electronically. Check the adjustment first, in other words. Then check the switch again as per the Bentley manual. The microswitch could also be faulty or really dirty. Maybe it's stuck? Yeah, the wiring could be bad too, as well as the ECM.
