Microswitch not engaging when hot

[Fox2506]

I tried to find the step by step instructions on how to adjust the throttle meticulously, but can't remember where it is.

I have a really good idle, below 1k RPM (good for an upgraded engine), but when the engine is hot, the throttle arm will only trip the microswitch if I tap the pedal (common, I know). I'm afraid I'll just have to sacrifice the low idle and back off the throttle contacts. I've tried several things that helped, but eventually fail once the engine heats up.

I shortened the balljoint arm as much as possible to make the throttle spool spring help pull back on the valve arm. It worked for a bit. If I could shorten it more, I feel like that would do the trick.

Also, I noticed the ball stud on the valve arm has some play, which isn't helping. Is this normal?

Has anyone ever added an extra spring to help the throttle arm return?

[opethmike]

When I was running K-Jet, I had the same problem. My issue was resolved after I took apart the throttle spool and greased everything judiciously.

[jawn101]

I have a similar issue, but blipping the throttle doesn't fix it. My idle is smooth at 750 when cold, but after warming up it hovers around 900. Still smooth as can be, just higher. Vacuum advance is verified hooked up and working... Weird. I did lengthen my quadrant arm a half turn recently to correct the idle micro switch not engaging, which worked. Can't remember if this issue started at the same time.

[David T]

When I was running K-Jet, I had the same problem. My issue was resolved after I took apart the throttle spool and greased everything judiciously.

Besides cleaning and lubricating everything the quadrant link ends are probably worn causing a lot of lost motion. Adjust it just a little bit longer. It has left-right handed threads and the ends are locked in with tiny spring clips like the door struts.

[Rich]

I shortened the balljoint arm as much as possible to make the throttle spool spring help pull back on the valve arm.

Did you also check to be sure that the return spring on the quadrant (the spool the accel. cable goes to) is clipped into the tighter of the two pairs of detents on top of the quadrant body?

[Fox2506]

Did you also check to be sure that the return spring on the quadrant (the spool the accel. cable goes to) is clipped into the tighter of the two pairs of detents on top of the quadrant body?

Pretty sure it is

[DeLorean03]

Photo for reference, thank you SpecialTAuto:

22819

This is a very "touchy" area of the idle system. You, in essence, have both a manual and an electric idle system working in tandem to keep the DeLorean's idle steady. Here is what I did to get a perfect 750 +/- 50 rpm:

First, you want to make sure your microswitch is just barely being tripped by the microswitch screw. With the engine off, turn your throttle spool nice and slowly to hear the microswitch disengage as you rev the throttle spool and engage as you release tension on the throttle spool. You should hear two very audible clicks - 1 for disengage and 1 for engage. Now...

1. Make sure the throttle spool spring and the linkage arm (the arm with the two ball joints on the ends) are thoroughly lubricated and in smooth working order.

2. Once you feel strongly that all is working smoothly, reference the picture above.

3. With the engine running, break loose the 8mm hexnut and turn the screw for the micro switch out until it does not trip the microswitch and you hear the idle rise. When that happens, manually trip/engage the microswitch with a microdriver/small screwdriver to ensure the microswitch is working properly. Now remove the screwdriver so your engine is idling high.

4. While your engine is idling high, break loose and back off the bottom bolt (turn it counter clockwise). What you are now doing is you are doing two things:

A. Closing the butterfly throttle plates (that you cannot see because the intake "W" pipe/elbows" are connected to the butterfly assembly - part #102856 here: Click to see (http://store.delorean.com/c-334-1-4-1-air-induction-system.aspx) ....)

B. As you are backing that resting plate screw off, once it is down far enough, the microswitch screw will also be coming down (naturally due to the design of the arm that holds the rest plate screw and the microswitch tripping screw), so you should soon hear your engine's idle come on down because the microswitch should be soon tripped. Now your throttle plates are closed and your microswitch is tripped.

5. Tighten down the hexnut on your rest plate screw. Make sure you hold your screw in place in a screwdriver as you tighten the hexnut, or the rest plate screw will move as you tighten the hexnut.

6. Give your microswitch screw a half more turn just to be 100% safe. Then tighten the hexnut down as you did in the previous step.

Now you should be nearly 100% good. If you're still have high idle issues, you can experiment with the length of the link arm (part #102555 seen here (http://store.delorean.com/c-334-1-4-1-air-induction-system.aspx)). I shortened the length of mine to where the ball joint just BARELY connected to the linkage arm, and I have had a nearly 100% perfect idle.

Of course, this is assuming your throttle cable is in solid working order as well as the electronic portion of the idle system.

"Actual mileage may vary" so to speak.

[David T]

Photo for reference, thank you SpecialTAuto:

22819

This is a very "touchy" area of the idle system. You, in essence, have both a manual and an electric idle system working in tandem to keep the DeLorean's idle steady. Here is what I did to get a perfect 750 +/- 50 rpm:

First, you want to make sure your microswitch is just barely being tripped by the microswitch screw. With the engine off, turn your throttle spool nice and slowly to hear the microswitch disengage as you rev the throttle spool and engage as you release tension on the throttle spool. You should hear two very audible clicks - 1 for disengage and 1 for engage. Now...

1. Make sure the throttle spool spring and the linkage arm (the arm with the two ball joints on the ends) are thoroughly lubricated and in smooth working order.

2. Once you feel strongly that all is working smoothly, reference the picture above.

3. With the engine running, break loose the 8mm hexnut and turn the screw for the micro switch out until it does not trip the microswitch and you hear the idle rise. When that happens, manually trip/engage the microswitch with a microdriver/small screwdriver to ensure the microswitch is working properly. Now remove the screwdriver so your engine is idling high.

4. While your engine is idling high, break loose and back off the bottom bolt (turn it counter clockwise). What you are now doing is you are doing two things:

A. Closing the butterfly throttle plates (that you cannot see because the intake "W" pipe/elbows" are connected to the butterfly assembly - part #102856 here: Click to see (http://store.delorean.com/c-334-1-4-1-air-induction-system.aspx) ....)

B. As you are backing that resting plate screw off, once it is down far enough, the microswitch screw will also be coming down (naturally due to the design of the arm that holds the rest plate screw and the microswitch tripping screw), so you should soon hear your engine's idle come on down because the microswitch should be soon tripped. Now your throttle plates are closed and your microswitch is tripped.

5. Tighten down the hexnut on your rest plate screw. Make sure you hold your screw in place in a screwdriver as you tighten the hexnut, or the rest plate screw will move as you tighten the hexnut.

6. Give your microswitch screw a half more turn just to be 100% safe. Then tighten the hexnut down as you did in the previous step.

Now you should be nearly 100% good. If you're still have high idle issues, you can experiment with the length of the link arm (part #102555 seen here (http://store.delorean.com/c-334-1-4-1-air-induction-system.aspx)). I shortened the length of mine to where the ball joint just BARELY connected to the linkage arm, and I have had a nearly 100% perfect idle.

Of course, this is assuming your throttle cable is in solid working order as well as the electronic portion of the idle system.

"Actual mileage may vary" so to speak.

The order is not correct. If you are going to be doing all of these adjustments "from scratch" the very first one is the stop for the throttle plates (butterflies). It is done with the motor not running and you remove the W pipe. You want to get them closed but you do NOT want to put any stress on them closing any tighter. That is what the stop is for. If the plates touch the sides and are forced past that point repeatedly the screws holding them to the throttle shaft will fatigue and break. Unless you see the paint on the stop screw disturbed you should not have to touch it, it can't change by itself and if it wasn't disturbed it is most likely just where it should be.
The adjustment for the micro switch can change, as the switch ages the trip point can change. You should use a continuity meter also, sometimes even though you hear it click it doesn't make contact. If that happens you must replace it. As for the throttle cable, you should relubricate the cable as per the recall.

[DeLorean03]

sometimes even though you hear it click it doesn't make contact. If that happens you must replace it. As for the throttle cable, you should relubricate the cable as per the recall.


If you do what I suggested with the engine running, a click with the engine running and the idle going down means the continuity is fine.

Respectfully, you and I typed the same thing in different order of steps. The end result is the same.

For whatever reason if something DOES get disturbed or things somehow do get out of adjustment, I'd want to know how to adjust this stuff just in case. That's why I typed out a step-by-step process or list of steps.

[David T]

If you do what I suggested with the engine running, a click with the engine running and the idle going down means the continuity is fine.

Respectfully, you and I typed the same thing in different order of steps. The end result is the same.

For whatever reason if something DOES get disturbed or things somehow do get out of adjustment, I'd want to know how to adjust this stuff just in case. That's why I typed out a step-by-step process or list of steps.

Yes, we did say the same thing, just not in the same order. The problem though is the order does matter because these adjustments affect each other so if you do it in the wrong order the end result is not right. The reason I suggest using a meter is because I have seen micros that were erratic and did not always trip or trip at the same point. You might not hear that from the motor as easily as seeing it on a meter. Typically the idle micro gets damaged because it is misadjusted. People use it as a throttle stop and it gets "overtraveled". The other screw is the throttle stop and it's purpose is to prevent overtravel of the throttle plates. The idle micro screw gets set to just trip the micro and then about a 1/4 turn more once the throttle stop is set.

[DeLorean03]

Typically the idle micro gets damaged because it is misadjusted. People use it as a throttle stop and it gets "overtraveled".

Definitely agree. That is precisely why I said:




First, you want to make sure your microswitch is just barely being tripped by the microswitch screw.



Best way to say it, we're both right. I was more systematic; you were more thorough with technical (and more accurate) details :thumbup:. Both our cars idle great, so hey, I can live with that :cheers1:.

[Elvis]

In several of these hundreds of idle threads I wrote how to overcome this problem.

try this:
when hot and the idle is high - don't touch it, just turn off the engine and restart it.
where is the idle now ??

When it's down at 775rpm again, then you have the vacuum problem which can easily be
solved with the spring solution that I posted several times - with pictures.

[Ron]

+1

...or the hoses for the vacuum solenoid are reversed (no way to vent)....

[jawn101]

In several of these hundreds of idle threads I wrote how to overcome this problem.

try this:
when hot and the idle is high - don't touch it, just turn off the engine and restart it.
where is the idle now ??

When it's down at 775rpm again, then you have the vacuum problem which can easily be
solved with the spring solution that I posted several times - with pictures.


+1

...or the hoses for the vacuum solenoid are reversed (no way to vent)....

Well, I dunno about anyone else but I'm definitely gonna try this tonight. I am 99.999% sure my vacuum hoses to the solenoid are correct, but anything's possible :)

[DeLorean03]

Speaking from experience, I had a bad/sticking throttle cable that had my car idling at 1000+ when warm, and when I turned my car off and back on, it was at 775rpm.

Elvis, is your post assuming that you can rev the throttle to make the idle come down to normal too? Just wanted to clarify as I am honestly curious/don't know.

[DMC Fanatic]

I also just adjusted those two screws recently on my car and when I rev the engine the idle takes a really small "dip" and then settles to 775rpm. Its not EXTREMELY noticeable but enough to annoy me. It usually does it more when the engine is cold than hot. The idle also stays the same at 775 cold and hot. Is this normal or should I maybe tighten the lower screw in a hair more?

[DeLorean03]

I also just adjusted those two screws recently on my car and when I rev the engine the idle takes a really small "dip" and then settles to 775rpm. Its not EXTREMELY noticeable but enough to annoy me. It usually does it more when the engine is cold than hot. The idle also stays the same at 775 cold and hot. Is this normal or should I maybe tighten the lower screw in a hair more?

Can you get a video of this ? Is it noticeable enough that you wonder if the engine might stop running, or is it VERY small - like - as if a spark plug just barely misfired?

[DMC Fanatic]

It seems pretty minor actually. Do you think its anything to worry about?

[DeLorean03]

It's kinda subjective. You could hook KJet pressure gauges and see if the fuel pressure changes (shouldn't) at all. You could also get a fancy-dancy ignition timing light like this one here (http://www.sears.com/craftsman-professional-digital-timing-light/p-00914066000P), and connect it to one spark plug wire at a time and see if there's any change in the strobe light pattern/rpms when the "small miss" occurs.

It's one of those "if it bothers you now...it prolly will later..." kinda things - all subjective.

[DMC Fanatic]

Sorry I should have mentioned this earlier: Before I readjusted the two screws, my idle would jump from 775 to like 950 rpms when hot and it never dipped. This started after the adjustment. The reason why I adjusted it is I read somewhere on this forum that your supposed to adjust the throttle screws on a hot engine to maintain the 775 rpms.

[David T]

Sorry I should have mentioned this earlier: Before I readjusted the two screws, my idle would jump from 775 to like 950 rpms when hot and it never dipped. This started after the adjustment. The reason why I adjusted it is I read somewhere on this forum that your supposed to adjust the throttle screws on a hot engine to maintain the 775 rpms.

The systems on the Delorean are not all that complex nor are they interconnected. They are each doing "their own thing" so to speak and can cause hunting and surging, The better in tune, the newer the parts, the less air leaks, the less noticable. Things are almost always better once warmed up but if it is all working right it can work well even cold or warm. Since the K-Jet is basically a mechanical injection system it can take some tweaking to get it running right and it can't compensate like modern ECU controlled systems for varying conditions. In your case it may just be a sluggish response from the idle motor because it has some gunk in it. Take it off and spray some carb cleaner into it and shake it around till you feel the shutter rotate freely. BTW, you do not adjust the air screws to set idle speed. They should be lightly closed all the way. The idle speed is set by the idle ECU and the idle motor once the throttle arm hits the idle micro. You also do not adjust the throttle stop screw or the idle switch screw to set idle speed.

[Ron]

Well, I dunno about anyone else but I'm definitely gonna try this tonight. I am 99.999% sure my vacuum hoses to the solenoid are correct, but anything's possible :)
Easy check is to connect a timing light, rev the engine, let it idle, then see if the timing is high but drops to normal when you remove the hose going to the distributor.
If you don't have a timing light, when they are backwards, you can usually hear the solenoid "pop/ping" and the idle will drop...

[Bitsyncmaster]

The throttle can stick with the engine running but work perfectly with the engine off. It's the engine vacuum on the the closed throttle plates that makes things not move smoothly. It tries to hold those plates open a little.

You can use a low pressure micro switch.
You can use more spring pressure.

Major problem with non working idle switch is your ignition timing runs advanced. I did some testing on a warm engine and idle ECU disabled and adding vacuum advance with engine at normal idle bumped the idle RPM up 300 to 500 RPM. That gain of RPM most likely is too much for the idle system to compensate for and the result is higher than 775 RPM with a warm engine. The idle switch has very little effect itself on the idle ECU.

[Ron]

I also just adjusted those two screws recently on my car and when I rev the engine the idle takes a really small "dip" and then settles to 775rpm. Its not EXTREMELY noticeable but enough to annoy me. It usually does it more when the engine is cold than hot. The idle also stays the same at 775 cold and hot. Is this normal or should I maybe tighten the lower screw in a hair more?


It seems pretty minor actually. Do you think its anything to worry about?


Sorry I should have mentioned this earlier: Before I readjusted the two screws, my idle would jump from 775 to like 950 rpms when hot and it never dipped. This started after the adjustment. The reason why I adjusted it is I read somewhere on this forum that your supposed to adjust the throttle screws on a hot engine to maintain the 775 rpms.
This sounds normal to me...When the engine is cold, the dwell is set to a given value, the vacuum advance is disabled... Once it is warm, the system varies dwell, if the screw is adjusted correctly. So, it sounds like you set the screw correctly/close and are now just seeing the relatively long time it takes it to settle down "naturally" when cold (open loop/dumb) and comparing it to the time it takes the system to handle it (closed loop/smart) and bring it back into spec, when warm. (It's not as smart/fast as modern systems which handle cold/hot etc but better than most carb setups across the board.)
If it were extreme, I would suspect the WRU not applying the correct Control Pressure (especially when cold), delay valve, vacuum routing/leak, throttle valve springs, etc.
(BUT, all bets are off with modified cams using stock components and settings ;-)

[DMCMW Dave]

If you can manually push the throttle closed and it idles down, the problem is all in the linkages. If you close the throttle all the way, and the idle stays high but goes back down if you shut the engine off and then restart it, the decel valve springs are bad. (These are the small valves built into the throttle blades). This can be confirmed by a visual inspection of the springs (with the W-pipe off).

[Ron]

The throttle can stick with the engine running but work perfectly with the engine off. It's the engine vacuum on the the closed throttle plates that makes things not move smoothly. It tries to hold those plates open a little.

You can use a low pressure micro switch.
You can use more spring pressure.

Major problem with non working idle switch is your ignition timing runs advanced. I did some testing on a warm engine and idle ECU disabled and adding vacuum advance with engine at normal idle bumped the idle RPM up 300 to 500 RPM. That gain of RPM most likely is too much for the idle system to compensate for and the result is higher than 775 RPM with a warm engine. The idle switch has very little effect itself on the idle ECU.
+1 !!!

(This is why I like Elvis' spring fix and to set the plates barely-barely open...allows for wear in the linkage, shaft, base, etc. It's not that touchy...even so, the ISM will compensate unless one gets ridiculous).

[Fox2506]

Not sure what you guys have gotten into, but I fixed it. Yes, some of the fixes are common practice, but just for the record:

Shortened the link arm to make the spool and throttle lever springs work in tandem. Didn't work but it was a step in the right direction.

Problem 1: the throttle cable was too tight and was keeping the spool from returning to rest, where it provides optimal spring assistance on the throttle lever. So I slackened it.

Problem 2: the microswitch contact was over-engaged and rebounding the lever. backed it off to the point of barely contacting

Works fine now.

[Grover]

From another thread in which Dave at Midwest posted. This worked for me when I had the same problem you are describing.

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.