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Idle speed sucks

GVR-4

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Apr 22, 2002
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Location
Asheville, NC USA
I'm ready to sell this pile of crap. I've been working on trying to get the idle speed under control for weeks and have made no progress. Please only offer useful suggestions.

Background:

Idle surge gradually got worse about 3 months ago, so I decided to get rid of the FIAV. I removed the throttle body, FIAV freeze plug and screwed in the plunger (or whatever it's called) so it would seal off completely (per Jeff O.) and replaced the freeze plug sealing it with some Ultra Grey. The idle surge was much better, but idle was ~1500.

I replaced the BISSS o-ring, ISC stepper motor, set the throttle closed switch and TPS. I followed the guidelines for setting base idle by grounding pin 10 of the diagnostic port to put the ISC stepper motor in the middle of its range and grounded the lead for setting base timing. I can get the idle speed to stabilize at 800 under these conditions, but when I remove the ground from pin 10, the idle rises 200-300 rpm. When I remove the ground for setting base timing, the idle rises ~400 rpm and I am back at 1200-1500 rpm.

My next idea is checking for intake leaks again. Has anyone else dealt with this issues like this?

More background:

I have had ECMLink since about January and have not taken the time to learn how to use it as well as I want, so maybe I don't have something on it set correctly.

The biggest frustration is this is my daily driver, I am working mandatory 10-hour days and I have a family. Wrenching is no fun with time constraints! Please help.
 

turbowop

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Apr 29, 2001
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Yakima, WA
I know Jeff said to screw in the plunger, but I've never actually known anybody to do it. Are we sure it completely seals it off by doing this?
 

Lonewolf64

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May 17, 2006
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1,197
Location
Birmingham, Alabama
Are you sure that your throttle body is properly grounded to the chassis of the car? That problem caused me to have an unusually high idle that would not stabliize after setting the idle the proper way with the BISS screw.
 

GVR-4

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Location
Asheville, NC USA
Not sure about the plunger thing, Mark.

Yes, the throttle body is well-grounded:


 

Quoting GVR-4:
I have had ECMLink since about January and have not taken the time to learn how to use it as well as I want, so maybe I don't have something on it set correctly.



The fact that you *can* get the idle to drop to 800 with the pin grounded, and then it RISES when ungrounded, would seem to indicate to me that it is something with the DSMLink that is telling it to raise the idle. Have you posted this question on their forum? Do you have an old chip you can throw in instead? Is the DSMLink connected while you are also grounding pin #10? Does the DSMLink have its own screen for enabling the "idle setting" feature instead grounding it manually?
 

GVR-4

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Asheville, NC USA
Thanks for the response, Jeff. I figured you would be able to help.

The fact that you *can* get the idle to drop to 800 with the pin grounded, and then it RISES when ungrounded, would seem to indicate to me that it is something with the DSMLink that is telling it to raise the idle.

I agree. I looked through the tabs briefly tonight, but nothing jumped out at me.

Have you posted this question on their forum?

No. I would search and read first and I haven't yet.

Do you have an old chip you can throw in instead?

Yes. I still have the last one you burned for me and have thought about putting it in to see if the problem goes away or not.

Is the DSMLink connected while you are also grounding pin #10?

No. ECMLink plugs in to the diagnostic port.

Does the DSMLink have its own screen for enabling the "idle setting" feature instead grounding it manually?

Yes. You can ground the timing adjustment to the ECU and ground the ISC to the ECU using a check box.


Frankly, I am done working on this problem until next weekend at the earliest, except for maybe reading some more. I was just hoping someone would say "Oh yeah, I had the exact same problem and here's how I fixed it."
 

prove_it

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Jul 3, 2008
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Location
Sioux Falls, SD
I also have DsmLink V3, helpful tip would be to go into the RPM/TPS menu and check the boxes at the bottom for idle switch. Make sure that the boxes are checked right. There are three boxes to check:

enable Idle switch operation
Disable Idle switch while moving
simulate idle switch from TPS

From what you wrote I would recommend to have the first and third boxes checked. DO NOT check the middle box. I tried that and I had idle problems.
Also run the datalog and display your tps, both the % and voltage. Check to make sure your closed throttle voltage is close to .40 volts and the percentage is at 0% until you crack the throttle even just a hair. You can adjust the tps via DSMLINK on the same menu as before. Adjusting this will make a big difference.

It sounds like everything mechanically functional since the idle will drop when you ground the connector. I truly believe this is the problem.
You didn't mention your version of DSMLINK, but if you have V3 you need to check the direct access menu for temp based idle air adjust. Change it all to stock if it isn't. This will help narrow some possibilities down for you.

I hope this helps, I these settings can easily be overlooked (I did it once) and give you a huge headache. Like I said, mechanically it sounds to be all functioning correctly so I think it's in the tune and there is a conflict which is throwing everything off.
Good luck! Let me know what your settings are too.

*If you can save the ecm file and eda files and send them to me if you want. I can look them over and see if I can find something*
 
Last edited:

prove_it

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I was reading some old posts and I read about grounding the throttle body. Check to make sure your body is grounded. The idle switch won't ground when you close the throttle since there is no ground path.
Click me
This could be your problem also.
 

GVR-4

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Apr 22, 2002
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Location
Asheville, NC USA
Thanks for all the specific suggestions. I'll read all this again more thoroughly next weekend when I have the time to sit in the car with the laptop. Much appreciated.
 
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