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Idle adjustment problems

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droppinbottom

Banned Member
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Nov 7, 2005
####, Yukon_Canada
Well guys I have never had a idle problem untill recently. I installed dsm link and in the process I made sure to check my base timing, fuel pressure, boost leak, etc. I had never put a timing light on the motor since it was built because the builder informed me that with a dsm he never put a light on any of his motors for tuning. I was instructed to set desired boost level and then pull timing untill there is no knock.

After setting timing by a light I notice my idle is higher and when the motor is cold I get idle surge. It will initially idle at about 1900 for a few seconds and then it will hold 1500rpms and then blip down to about 1200 and rise to 1500 and keep repeating untill the motor is fully warm at which time it will idle steady at 1100 with all acc off and with lights on it will be about 950.

The problem I am having with adjusting the BISS is when I look at the BISS screw, there is a reddish substance in there that looks almost like red thread sealer got pored in it and it is all hard now. I can take a small screw driver and scrape away a little bit of the red substance but I dont think I will ever be able to get a screwdriver to adjust any screw.

Here is a pic but I don't know if it will help with what I am describing as it is still hard to see.

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Thanks guys for the help and sorry if this post is not in the proper section as I was not positive on which area to post in.
 
Hard to tell from your picture, but given what you're describing, I'd be inclined to believe that whatever the "red thread sealant" type stuff that was poured over the BISS is can't be a good thing (LOL). My recommendation would be to replace the BISS entirely, just to be on the safe side. It should be safe to use a small drill bit to get it backed out, since it probably won't want to move much in its current state. haha.

With inexpensive parts like the BISS, it's always a good idea to just start fresh and do it right if you have the chance :) I'm pretty confident that this would alleviate your high idle issue - if not, we can troubleshoot further from there.
 
I just want to make sure I dont screw anything up. I am supposed to have a tune done in two weeks but I am going to make sure everything is as good as I can get it before I go since the shop is about a 3.5hr drive and getting a sat appointment is not easy.

Just to confirm, when I went to check my timing with a light I found that it was retarded quite a bit (maybe as much as 10degrees) and it would idle fine. By advancing the timing to 5 BTDC it made the motor idle faster even while the motor is up to temp? Old idle 850 with retarded timing and 1200 with timing set to 5 BTDC.
 
You should be able to set your idle with DSMLink. If it is idling funny at startup, check the FIAV. Usually it is the problem when it clears once the car reaches operating temp. Hard to adjust idle with BISS since the computer will automatically compensate and make it go back to where it was set.
 
Advancing timing will increase idle speed. The problem is that the ISC adjusts very slowly, especially in the downward direction. You would have to drive/idle it for a while to see if it will come back down. I would set the timing to what it is supposed to be since you have dSMlink. There is no reason to not give the ECU the base timing it expects to have. ALL timing adjustments made by the ECU assume that actual timing matches target timing, which is determined by setting "base timing." Then give it time to adjust the idle down.

Capture IdleSw, LearnedIdleAdj, and IdlePosition in DSMlink. With the car idling, IdleSW has to be a 1, or the ECU will not attempt closed loop control of idle speed. Ideally it will switch from 0 to 1 below 1 or 2% TPS. Learned (long term) should be around 144, and ISC position (short term) should be around 30. If the learned value is over 144, open the BISS, and vice versa. Of course this assume you can actually use your BISS. At the least check those values and see if they are way out of wack. Just like fuel trims, you need to center the ISC "trims" since it only has so much travel in either direction.
 
Thanks for the information. I logged those values and I know my idlesw works since it is 1 at idle and it changes to 0 once I give it a little throttle.

My iscposition is 0 and my lrndldleadj is 124. I am assuming that I need to adjust the BISS based on the previous post but as my delima would have it something is preventing me from doing that.

Has anyone ever tried to drill out a screw like this as I have never done it yet.

Thanks for the help again

Dan
 
Regarding the BISS screw dilema.

Try drilling into the substance with a drill bit the size of a pencil lead. Go very slowly and run the drill at a low rpm (baby speed). You should be able to feel when you hit the metal screw head. Do not hit the edges of the hole with the bit. If the substance does not crumble or crack, continue to drill more holes and pick at it with a pick tool, small screwdriver, or bent wire to remove the substance.

Repeat: Do not hit the edges of the hole with the bit. Drill like you are in slow motion
 
Whoooo Hoooo I finally got the screw loosend up. I used a bit of gasket remover to loosen up the threadlocker and scraped enough away to finally get the screw to turn. Finally the idle is being controlled by link. I know I will have to do a little more adjusting but the biggest problem is taken care of.

On a side note just wanting to make sure I am thinking correctly. When I use gnd timing on link it will be just like using the gnd timing under the hood when adjusting the biss?

Thanks for all the replys gus.
 
Make sure that grounding diag (either in DSMlink or on firewall for 95s) actually centers the ISC. IIRC, it doesn't, but it's been a few years since I messed with it. If it does, your all set. If it doesn't just set it the old fashioned way. Get LearnedIdleAdj to 144 over time. It takes forever for it to lower that number, so if you are a good bit over 144, reset the ECU to speed up the process (will start at 144).
 
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