Adjusting Idle Speed

[mluder]

I just finished re-assembling the top side of my engine after replacing the water pump and repaining the intake, w-pipe, etc. as well as the fuel distributor, etc.

In the process, the curb idle screw and the screw that contacts the idle speed microswitch have been mucked up.

Is there a process for resetting them? I know the microswitch screw is designed to engage the switch when the throtle is released. However, how do I adjust the curb idle screw to set the rest position?

Right now the engine runs but there is an intermittant scraping sound that seems to come from the pressure plate on fuel mixture control unit. I think it is actually air being sucked into the small gap as when the engine is idling, the plate is being pulled down ever so slightly and there is about a 1/16 to 1/32 gap.

Any thoughts?

Cheers.
Steve

[Bitsyncmaster]

Just back it out till no contact, turn in untill contact and then add maybe a half turn. I have not checked the amount to turn it in but my guess is between 1/2 to 1 turn.

[DMCMW Dave]

I

Is there a process for resetting them? I know the microswitch screw is designed to engage the switch when the throtle is released. However, how do I adjust the curb idle screw to set the rest position?



Cheers.
Steve

Un-official but it works:

1 - Back both screws out so that the throttle is really closed.
2 - Turn the bottom screw in so that it just contacts the stop. Go another 1/2 turn.
3 - Turn the top screw in until the microswitch clicks. Go another 3/4 turn.
4 - Start the engine and let it get completely warmed up. Fans should cycle at least twice.
5 - Turn the top screw in slowly until the idle speed starts to increase. Every 1/2 turn, turn the top screw in the same amount to maintain pressure on the microswitch. Now back the lower screw out until it is just stops slowing down, i.e. just at 775 RPM.
6 - Back the top screw out until the microswitch clicks, then turn it back in until the switch just clicks and then another 3/4 turn.
7 - Lock the lock-nuts without turning the screws.

This makes sure that, when warm, the idle speed motor is more or less closed. This gives the best performance (margin for opening) when cold, and tends to minimize instances of the engine dying when the throttle is slammed shut at high rpm.

[mluder]

Thanks, Daves.

I will let you know how it goes.

Coincidentlally - I've got a nice idle hunt going right now too. I'm assuming that it's due to the engine being cold as well as probably a need to adjust the mixture. I replaced all the vacuum lines and the timing chain gasket and the rocker cover gaskets, as well as the spark plugs so I'm sure things are off from my previous conditions.

If I allow the engine to come up to temp - i.e. cycling the fans twice - I assume I adjust the idle speed first. Then the mixture with a dwell measure?

Cheers
Steve

[Bitsyncmaster]

Adjust the curb idle screw now with the engine off. You don't adjust the normal idle speed. That is set to 775 RPM via the idle ECU. You will need to adjust the mixture with a dwell meter after doing all that work.

[DeLorean03]

5 - Turn the top screw in slowly until the idle speed starts to increase. Every 1/2 turn, turn the top screw in the same amount to maintain pressure on the microswitch. Now back the lower screw out until it is just stops slowing down, i.e. just at 775 RPM.


Hey Dave,

Excuse me for asking. For the second part, did you mean "Every 1/2 turn, turn the bottom screw in the same amount..." ?

[DMCMW Dave]

Hey Dave,

Excuse me for asking. For the second part, did you mean "Every 1/2 turn, turn the bottom screw in the same amount..." ?

No - the bottom screw sets the throttle stop, the top one is the microswitch.

[mluder]

No - the bottom screw sets the throttle stop, the top one is the microswitch.

I was confused about that too. Dave said, "5 - Turn the top screw in slowly until the idle speed starts to increase. Every 1/2 turn, turn the top screw in the same amount to maintain pressure on the microswitch. Now back the lower screw out until it is just stops slowing down, i.e. just at 775 RPM."

It seems like you are saying the same screw - Are you sure you don't mean turn the BOTTOM screw until the idle speed... and then turn the TOP screw the same amount? I assumed that's what you meant.

Cheers
Steve

[DMCMW Dave]

Yeah - my bad. #5 is the only one wrong.

The bottom one is the stop screw, the top one is the microswitch. The idea is to open the throttle as far as possible while maintaining 775 rpm, and keep the switch engaged (pressed).

Long day I guess.

[Jonathan]

Is one aspect of that adjustment the part considering it as a lever arm, such that if the screws are both fully backed out with the throttle completely at rest, then lengthening the top screw is actually pushing the lever arm away a little more, hence the bottom screw isn't touching anymore? Where you are aiming to have it adjusted to satisfy both of the main conditions (being that the idle speed microswitch is engaged when it should be, and that the lever arm is completely at rest when it should be) BUT your adjustment is trying to get it very close to the "switching point" for each of these conditions? i.e. cutting out the lag/delay/slack.

[mluder]

Yeah - my bad. #5 is the only one wrong.

The bottom one is the stop screw, the top one is the microswitch. The idea is to open the throttle as far as possible while maintaining 775 rpm, and keep the switch engaged (pressed).

Long day I guess.

No worries, Dave. I appreciate the help.

I'll let you know how it goes.

Cheers
Steve

[DMCMW Dave]

Is one aspect of that adjustment the part considering it as a lever arm, such that if the screws are both fully backed out with the throttle completely at rest, then lengthening the top screw is actually pushing the lever arm away a little more, hence the bottom screw isn't touching anymore? Where you are aiming to have it adjusted to satisfy both of the main conditions (being that the idle speed microswitch is engaged when it should be, and that the lever arm is completely at rest when it should be) BUT your adjustment is trying to get it very close to the "switching point" for each of these conditions? i.e. cutting out the lag/delay/slack.

The bottom screw is what keeps the throttle from closing all the way. The top one triggers the microswitch. The top one should NOT be limiting travel of the throttle linkage.

The goal is to have the bottom one hold the throttle open as far as possible without increasing the idle speed, and the upper one to **just** trigger the microswitch without impacting the throttle itself.

[Grover]

Un-official but it works:

1 - Back both screws out so that the throttle is really closed.
2 - Turn the bottom screw in so that it just contacts the stop. Go another 1/2 turn.
3 - Turn the top screw in until the microswitch clicks. Go another 3/4 turn.
4 - Start the engine and let it get completely warmed up. Fans should cycle at least twice.
5 - Turn the top screw in slowly until the idle speed starts to increase. Every 1/2 turn, turn the top screw in the same amount to maintain pressure on the microswitch. Now back the lower screw out until it is just stops slowing down, i.e. just at 775 RPM.
6 - Back the top screw out until the microswitch clicks, then turn it back in until the switch just clicks and then another 3/4 turn.
7 - Lock the lock-nuts without turning the screws.

This makes sure that, when warm, the idle speed motor is more or less closed. This gives the best performance (margin for opening) when cold, and tends to minimize instances of the engine dying when the throttle is slammed shut at high rpm.

A big thumbs up and thank you for this. Seems to have fixed my sticking idle by doing this after shortening the rid linkage a bit.

[mluder]

The bottom screw is what keeps the throttle from closing all the way. The top one triggers the microswitch. The top one should NOT be limiting travel of the throttle linkage.

The goal is to have the bottom one hold the throttle open as far as possible without increasing the idle speed, and the upper one to **just** trigger the microswitch without impacting the throttle itself.

Well, Dave. I tried my best.

I can't get the idle speed low enough. I back the lower screw out and have to essentially remove it and the idle still sits at about 800-900. If i insert the screw until it just touches and turn a half turn it shoots up to over 1000. I made sure the microswitch screw was not holding open the throtle but still engaging the switch but it still seems hign.

Not sure what else to do... Is it possible that the lower screw is just unnescesary

Cheers
Steve

[mluder]

Here is how the idle sits with no lower screw in place and the switch screw just engaging the switch + 3/4 turn.

13214

Here is what that looks like.

13215


13216

Here's how they used to set...

13229

Thoughts?

Cheers
Steve

[Bitsyncmaster]

Well, Dave. I tried my best.

I can't get the idle speed low enough. I back the lower screw out and have to essentially remove it and the idle still sits at about 800-900. If i insert the screw until it just touches and turn a half turn it shoots up to over 1000. I made sure the microswitch screw was not holding open the throtle but still engaging the switch but it still seems hign.

Not sure what else to do... Is it possible that the lower screw is just unnescesary

Cheers
Steve

I had that same problem for years. Finally found out the deceleration valves on the throttle plates had bad springs. Probably not your problem but take a look at them. You need to remove the W pipe to see them.

[mluder]

I had that same problem for years. Finally found out the deceleration valves on the throttle plates had bad springs. Probably not your problem but take a look at them. You need to remove the W pipe to see them.

Thanks, Dave.

I don't think that's the problem (I hope). I didn't seem to have that problem before I took everything apart and recalling that you had had problems with those springs I was real careful not to mess with them.

Just out of curiousity what did you do before you replaced those springs - just have a slightly high idle and run without the bottom screw? I'm kinda thinking that's what I might do.

Is there a way to test the deceleration valves or a tell tale sign without taking things apart?

Cheers
Steve

[DMC5180]

Hmmm, 800-900 thats just right IMO. 775 is to low for alternator loading. Plus it's nicer pulling away from a stop with that extra rpm.

[mluder]

Hmmm, 800-900 thats just right IMO. 775 is to low for alternator loading. Plus it's nicer pulling away from a stop with that extra rpm.

So you think it's ok to run without that lower screw... I mean it's only there to adjust as need be but if it's not needed???

Cheers
Steve

[Bitsyncmaster]

Thanks, Dave.

I don't think that's the problem (I hope). I didn't seem to have that problem before I took everything apart and recalling that you had had problems with those springs I was real careful not to mess with them.

Just out of curiousity what did you do before you replaced those springs - just have a slightly high idle and run without the bottom screw? I'm kinda thinking that's what I might do.

Is there a way to test the deceleration valves or a tell tale sign without taking things apart?

Cheers
Steve

Yes, I ran with the bottom screw fully backed out. This is what bad ones look like.

[mluder]

Here's a vid of the car idleing... NOtice that teh dwell is acting kinda funny too. It's not swinging like it normally does and it actually appears to swing with the idle hunt.


https://plus.google.com/photos/114080774471355287565/albums/5788585236986119681/5788585242056026082

I'm at a loss

Cheers
Steve

[mluder]

Bump...

Looking for more input if popssible.

Cheers.
Steve

[mluder]

I had that same problem for years. Finally found out the deceleration valves on the throttle plates had bad springs. Probably not your problem but take a look at them. You need to remove the W pipe to see them.

I'm starting to think the deceleation valves is the problem. I haven't inspected them physically but I have been driving the car for a bit now and it's exhibiting some characteristics that point to that.

When the engine is warm if I slow down to stop at a light or somthing, the idle sits way high - sometimes as mucha s 1500 RPMs. If I tap the accelerator briefly it settles back into the 800 900 range.
I verified that when it sits at the high idle (1500) that the arm on the butterfly assembly is fully in the rest postion so the butterfly should be closed. The only thing I can gather is that the deceleration valves are allowing too much air to pass through and running hte idle high.

Were you able to source just the springs and if so how or where?

Cheers
Steve

[Bitsyncmaster]

I'm starting to think the deceleation valves is the problem. I haven't inspected them physically but I have been driving the car for a bit now and it's exhibiting some characteristics that point to that.

When the engine is warm if I slow down to stop at a light or somthing, the idle sits way high - sometimes as mucha s 1500 RPMs. If I tap the accelerator briefly it settles back into the 800 900 range.
I verified that when it sits at the high idle (1500) that the arm on the butterfly assembly is fully in the rest postion so the butterfly should be closed. The only thing I can gather is that the deceleration valves are allowing too much air to pass through and running hte idle high.

Were you able to source just the springs and if so how or where?

Cheers
Steve

I got another used throttle assembly. Even if you could find the springs, you would need a test bench to adjust them. They would have to be closed with normal idle vacuum. I don't know what they normally are set at. My guess would be 20 inches of mercury or more.

I did not have that problem you describe where you could tap the pedal and get the RPM to drop. Mine would just have 1000 RPM or more after the engine was hot even with the curb idle screw fully backed out.

[mluder]

I got another used throttle assembly. Even if you could find the springs, you would need a test bench to adjust them. They would have to be closed with normal idle vacuum. I don't know what they normally are set at. My guess would be 20 inches of mercury or more.

I did not have that problem you describe where you could tap the pedal and get the RPM to drop. Mine would just have 1000 RPM or more after the engine was hot even with the curb idle screw fully backed out.

Hmmmm????

Well, I'm taking it to Toby at DMCNW tomorrow to give the car a once over and make sure I've got everything back together sufficiently and set correclty so I'll have him see if he can run down the problem.

Cheers
Steve

[David T]

The tension on those springs is not all that critical. It has to be enough to hold the valves closed at idle. You may be able to use them by just stretching them. If that doesn't work maybe take some springs out of some pens. The decal valves only operate during high RPM deceleration on a 5-speed. They are really non-functional for the automatics.
David Teitelbaum

[ssr60]

Steve,

Did you ever get the high idle problem worked out. I would be interested in finding out what was going on.

Scott

[mluder]

Hi, Scott.

Not yet. Still simmilar circumstances. High idle and and sticking in quick deceleration.

Couple of new things - Toby at DMCNW identified an exhauset leak forming on the driver side manifold near to the O2 sensor. This could contribute to the idle hunt as the lambda is not getting consistant readings.

I have in hand a new throtle assembly from DMCH but I have not had time to install it.

We are in the process of closing on a new home with a spacious 3 car garage so I will have a lot more room to work. Couple that with the packing, etc. I'm holding off starting any projects but I will update along the way as I swap the throttle assembly and replaced the exhaust manifold gaskets.

Cheers
Steve


Steve,

Did you ever get the high idle problem worked out. I would be interested in finding out what was going on.

Scott

[OverlandMan]

Steve,

Good luck with the move. I watched the video you posted a while back detailing the issue you're having. Unrelated to the idle issue it appears that your oil gauge/sender is not registering correctly. Looks like its bouncing between 80 (peg) and 60 psi.

My car has a similar issue though not quite the same. I'll take a similar video next time I think about it and post. Curious to see what your final resolution comes to be once you get settled in your new casa.

[mluder]

For what it's worth, I get odd readings on all my guages... Battery one often reads lower than 13/14 volts but I have tested at the battery and I'm getting enough from the alternator so....

I think it's a result of poor grounding. I have cleaned connections on them as I run accross them on other projects but have not set out to fully address every one.

Could also be a bad sender on the oil guage too.

Steve


Steve,

Good luck with the move. I watched the video you posted a while back detailing the issue you're having. Unrelated to the idle issue it appears that your oil gauge/sender is not registering correctly. Looks like its bouncing between 80 (peg) and 60 psi.

My car has a similar issue though not quite the same. I'll take a similar video next time I think about it and post. Curious to see what your final resolution comes to be once you get settled in your new casa.

[Jack]

13216
I know this is an "older" post, but was the third screw missing in this picture not in place when the car was idling high?

[mluder]

13216
I know this is an "older" post, but was the third screw missing in this picture not in place when the car was idling high?

Yep. I had taken it out completely and it was still idling around 1000 RPMs. I have since put it back in so it's barely threaded. Just enough to hold it in place.
I am convinced that the little springs on the valves inside butterfly assembly are shot. I have a new assembly to install but haven't had time to do the work yet.
I'm still driving and still having the occasional idle issue but notheing that keeps me from getting out and about.

Cheers
Steve

[cybercusp]

I had a high idle issue that was fixed this weekend. Since I got the car in August the "warmed up " idle had been slowly creeping up from 750 to 1200. Cold idle remained at 750. Replaced the butterfly valve and the warm idle is now 750.

[hippieman9]

Yep. I had taken it out completely and it was still idling around 1000 RPMs. I have since put it back in so it's barely threaded. Just enough to hold it in place.
I am convinced that the little springs on the valves inside butterfly assembly are shot. I have a new assembly to install but haven't had time to do the work yet.
I'm still driving and still having the occasional idle issue but notheing that keeps me from getting out and about.

Cheers
Steve

Have you figured out this issue? I have been experiencing a similar issue since I replaced my water pump. I would start th car and have 800 rpm idle. Drive it about 40 min or so and the idle was at 1500 rpms. Not sure what’s causing it. I just did the idle adjustment Dave explained early in this post. Haven’t been able to drive it, but seems as though the idle is at 900. Still checking thins out to see if maybe I missed something .

[mluder]

Have you figured out this issue? I have been experiencing a similar issue since I replaced my water pump. I would start th car and have 800 rpm idle. Drive it about 40 min or so and the idle was at 1500 rpms. Not sure what’s causing it. I just did the idle adjustment Dave explained early in this post. Haven’t been able to drive it, but seems as though the idle is at 900. Still checking thins out to see if maybe I missed something .

Things have settled down though I can't point to any particular fix... I've since replaced the fuel pump. That's about all I can say definitively. I'll have to refresh my memory and see if anything else jumps out in terms of adjustments, etc.

Cheers
Steve

[hippieman9]

Things have settled down though I can't point to any particular fix... I've since replaced the fuel pump. That's about all I can say definitively. I'll have to refresh my memory and see if anything else jumps out in terms of adjustments, etc.

Cheers
Steve

ok cool. Just wondering. Thanks!