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87 Carerra, 3.2 liter en
 
Join Date: Aug 2008
Location: Washington, DC
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Help With Adjusting Idle Control Microswitch

Okay:

After 3 1/2 years of trying to fix a no-start problem on an 87 911 I was finally able to get the darn car started and running. Believe it or not I had not heard the car run for over 3 years and I am now sitting here typing with tears of joy in my eyes just hearing the car run.

BUT ALL PRAISE TO INGO who held my hand throughout a month long process to get the car running. He walked me thru first getting a spark (because I had none) then walked me thru the fuel side and helped me diagnos fuel issues. Ended up getting a fuel pump and then the DME or brain had to be sent to him for repair.

By the way I want to note that Ingo tried everything in the book to get me up and running. He must have spent a month corresponding with me back and forth just trying to help me. He would not give up until he got me running. After we were getting no power to the injectors after knowing we had a new fuel pump and my fuel pressure in the rails was correct we deduced the problem being the brain not sending the signals out. I sent him the brain on a Monday he got it on Wednesday and had it back in my hands that same Friday. Woaloa!!! I was up and running after 3 1/2 years!!! Talk about fast and thorough service! And I want to note I had previously sent the brain out a couple years ago to a company I will not name and they supposedly fixed it (like I said supposedly). The day Ingo got my brain he sent me back photos showing me exactly what my problem was and how the circuitry had not been properly repaired. But let me stay positive!!!

Well now I am running. I just got one last issue. The car is really surging and runs steady for 20 mins or so as long as I hold my foot to the gas. In other words the car is not idling. Before coming to you guys I did a little homework and Steve Wong wrote something I want to check but as a non-mechanic I actually do not know how to go about doing it. He spoke about testing the Idle Control Microswitch and the linkage to the . He wrote:

"Your idle microswitch may not be activating. Its the plug by the throttle body that has a two pin connector on it. Use a test meter to check that it activates closed when the throttle is closed. If not working, the switch may either need to be adjusted or the linkage may be too tight. When the switch does not activate, the computer will think it is in part throttle mode, and want to idle up at 1500-1700 rpm."

1. Guys I am sorry to have to ask this but when he states "check that it activates closed when the throttle is closed" does he mean the meter should read 0.L? I simply do not know what that means.

2. Say my microswitch does need adjusting how do I go about this?

3. Lastly, when he states "the linkage may be too tight" how do I go about adjusting the linkage he speaks about.

Sorry for all of the elementary questions, but bear with me I am up and running and just need to be hand held a little more to make the final tweaks.

Again, thanks so much Ingo for hanging in there with me if you are out there hovering around somewhere

I'M RUNNING!!!!!

SrWilliams

Last edited by Srwilliams; 11-05-2016 at 10:05 PM..
Old 11-05-2016, 09:59 PM
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Do you have the Bentley Guide?

1. You simply go to the engine bay and pull on the throttle and slowly pull back to close position. You should hear an audible "click" indicating the switch is engaging. Engine off.

2. If you do not hear the "click" the idle switch needs to be re-positioned as referenced in the Bentley Guide, but before this, do #3.

3. The linkage adjustment is mainly done at the transmission bell housing, remove the ball cap, loosen the jam nut and turn the ball cap end out one turn and make sure there is slack at the throttle body. Maybe 1-2MM. If there is no slack, I concur the linkage is too tight and may cause the micro idle switch not to engage. if there is slack and micro switch still does not "click" then adjust the micro switch.

Hope this helps,

Jim
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Old 11-05-2016, 10:08 PM
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Real quick - your DME actually didn't keep the DME relay on after releasing the key from START to RUN and that was repaired. So now on to the idle switch:

The switch needs to activate (close) when the throttle lever turns back the mechanic throttle stop. This tells the DME to enter idle mode. I tested your DME and it correctly can detect this. So your issue is either the harness or the switch or the adjustment itself. The best way to test is to disconnect the DME and then connect an Ohm meter to pin 2 and pin 17 inside the DME harness connector. If your meter has a setting for making a sound for continuity set it to that. Test the meter by holding the test leads together. It should beep.

Then, when you measure on pin 2 and pin 17 with the throttle closed you need to see near zero Ohm and hear the same beep. If not try and pull the throttle lever towards its closed position.

The design of the throttle is such that there is an adjustable mechanic stop E. The return spring needs to return the throttle to that mechanic stop. If that doesn't work your throttle linkage is binding somewhere or the return spring is bad or missing. Do not adjust E as this requires special tools to set idle speed correctly.

The micro switch needs to be engaged (pressed) when the throttle is at its mechanic stop without acting itself as the mechanic stop. See the mechanic drawing. The screw E defines the mechanic stop and there still needs to be a very tiny gap D between the metal arm and the micro switch.



You can hear the micro switch clicking when opening and closing the throttle lever by hand. If your meter still doesn't show a low OHM reading when the switch is depressed its either damaged or the harness has a problem. You can also press the switch with a screwdriver and this needs to register on the OHM meter. If not then its an electrical issue in the switch or the harness.

Good luck,
Ingo
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Old 11-05-2016, 10:27 PM
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87 Carerra, 3.2 liter en
 
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To both Draco and Ingo:

The above from the two of you is exactly what I needed. I am on this in the morning

Thanks again guys

SrWilliams
Old 11-05-2016, 10:54 PM
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87 Carerra, 3.2 liter en
 
Join Date: Aug 2008
Location: Washington, DC
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Okay Ingo and Draco:

I did the test that both of you outlined last night.

With the engine off I disconnected the 35 pin connector and tested pins 2 and 17 for continuity and set the meter to beep as Ingo instructed. Got nothing. Then went to the engine bay and pulled the throttle towards me and as it got to the end of the pull the beep could be heard. Did this several times to verify.

1. Curious question: When I am standing outside of the engine bay and pull the throttle level towards me am i opening or closing the throttle? I ask this because when I do not pull the lever towards me I hear nothing and it is not until it is pulled completely forward that I hear a beep (if that is the case why would I necessarily hear a beep when I am inside the car and testing the 17 and 2 without anyone pulling the throttle lever forward---just curious?)

2. Here is a point I noted. When I pulled the throttle lever towards me the ohm meter beeped when the lever was 3/4 ways before reaching the end point and then continued to beep the rest of the quarter way. So, I was getting a continuity beep BEFORE reaching the end. I did this repeatedly with the same result. I found this confusing because Bently indicates that I am only supposed to get continuity at the end point with 0.L at all other points.

3. I figured my linkage needed adjusting and I tried to follow DRACO's instruction. I located the linkage at the tranny under the car. Draco wrote: "remove the ball cap, loosen the jam nut." I do not want to mess something up and so I stopped to ask the ridiculous question---Is the ball cap the metal ball with a sleeve to it that you pop off and then screw the sleeve part on the throttle cable. I m looking at the first picture on page 240-21 of Bently. I did not see anything to adjust at what that picture identifies as the actual "Throttle Linkage."
Like I said I stopped before dismantling anything because i did not want to mess anything up.

Last edited by Srwilliams; 11-06-2016 at 10:27 AM..
Old 11-06-2016, 10:23 AM
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1. opening, so pull the throttle arm toward the rear/you. If you could post a video that may help us see what you are doing???

2. I am having a hard to visualizing what you are doing, sowwy.

3. Yes, Linkage/rod not cable, actually the total linkage is made up linked steel rods except the cruise control attached to end of throttle arm.



There is the "ball cap" then the jam nut, loosen it then turn ball cap counter clockwise to loosen then tighten the jam nut, no need to over torque it. It can be easily put back to original position if need be.
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'85 Carrera Targa
Factory Marble Grey/Black * Turbo Tail * 930 Steering Wheel* Sport Seats * 17" Fuchs (r) * 3.4 * 964 Cams * 915 * LSD * Factory SS * Turbo Tie Rods * Bilsteins * Euro Pre-Muff * SW Chip on 4K DME * NGK * Sienes GSK * Targa Body Brace
PCA/POC

Last edited by DRACO A5OG; 11-06-2016 at 11:05 AM..
Old 11-06-2016, 11:03 AM
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