Slightly High Idle - I'm guessing O2 sensor?

[DavidProehl]

I've been reading a lot of high idle threads over the past several days and would appreciate a "yay" or "nay" based on my symptoms.

Symptoms

Idle right at 750 when it starts
After 1-2 minutes it will climb to about 1200 and stay there


Possible Contributing Factor

Car ran VERY rich about a year ago after accidentally swapping 2 spark plug wires, and resulted in a glowing cat. Probably did 50-75 miles like this of the course of about 4 drives before realizing there was a problem :mad1:


From what I've read the O2 sensor kicks in after it warms up, which is about 1 minute into idle. I also read that running rich can mess up the O2 sensor by plugging it up.

I have a new O2 sensor, but I'd likely first have to pay a shop to torch and remove the original one (it is in there WAY to tight). So I have no way to easily test this on my own by simply swapping it out. So I guess I'm asking what you think the odds are my O2 sensor is bad and do those odds warrant me spending $100 to have a shop pull the old one?

[DMCMW Dave]

I doubt that's the problem although it would not hurt to change it due to the heat issue. You can test it in place, they rarely fail without completely dying which you can detect by attempting a dwell meter CO adjustment.

I can't fathom a way that a bad O2 sensor would cause a high idle. More likely you have a bad or disconnected vacuum solenoid (or something related such as the idle speed microswitch or its wiring), and once the engine warms up you get ignition distributor vacuum when you shouldn't.

[opethmike]

First thing I would check is as Dave suggested, if you are getting vacuum advance at idle. When the car goes to high idle, pull the vacuum hose off of the distributor.

If the idle drops, you are getting vacuum advance at idle, which you should not be. You can confirm this by putting your finger on the end of the hose that you pulled off of the distributor and if you feel a vacuum, then you are indeed getting the advance that you don't want.

[DavidProehl]

Thanks for the quick responses, I'll give the hose disconnect test a try. Just to be sure I understand (haven't worked with any part of the vacuum system before).



Warm up car
Disconnect hose #29 (http://store.delorean.com/images/Category/large/2-4-0.gif) from the vacuum distributor, leaving it attached to the vacuum solenoid
If I feel a vacuum on the hose coming from the vacuum solenoid, then my solenoid is bad


Good to know it isn't the O2 sensor and that I was likely heading down the wrong path there.

[jawn101]

Between you and me it's always something, isn't it David. I had this happen recently too and it was just the electrical connector had fallen off the vacuum solenoid. Finding it back behind the motor was tough but hooking it up was easy and fixed the issue right away. Good luck!

[DavidProehl]

Yeah Jon, no kidding! I think my problem is that I get stuck on the simple things not having much car knowledge prior to owning my D.

Just went through the above procedure, no vacuum when hot. I think the vacuum is working.

That made me think a little deeper about how I was warming up the car, by revving the engine. This reminded me about step 1 when checking for high idle, make sure your throttle switch is fully disengaged. Wouldn't you know it, I push on the throttle switch and she drops from 1200 RPM back to 750. It is sticking. I feel a bit foolish now.

Now I guess I need to lube up my throttle cable or perhaps replace the spring attached to the throttle arm. Maybe both.

In any event, thanks for the tips! They got me thinking about the problem differently than I was.

[deloumis]

Thanks for the quick responses, I'll give the hose disconnect test a try. Just to be sure I understand (haven't worked with any part of the vacuum system before).



Warm up car
Disconnect hose #29 (http://store.delorean.com/images/Category/large/2-4-0.gif) from the vacuum distributor, leaving it attached to the vacuum solenoid
If I feel a vacuum on the hose coming from the vacuum solenoid, then mmy solenoid is bad


Good to know it isn't the O2 sensor and that I was likely heading down the wrong path there.

Not necessarily bad solenoid, could be wiring issue like in jawn's case.

[opethmike]

Warm up car
Disconnect hose #29 (http://store.delorean.com/images/Category/large/2-4-0.gif) from the vacuum distributor, leaving it attached to the vacuum solenoid
If I feel a vacuum on the hose coming from the vacuum solenoid, then my solenoid is bad


1 and 2 are correct.

3 is a possibility; but more likely is that your idle microswitch isn't being tripped. While you have your finger on the hose, push in on the idle microswitch. You should feel/hear it click, and vacuum should go away.

[AirmanPika]

Semi related...I have my own idle issue and didn't feel like creating a new thread.

Any thoughts as to what would cause high idle at engine start? I thought it was microswitch because if I disconnect my switch and jump the two wires, idle drops to norm...but I'm assuming this isn't a good thing to do. Thing is I replaced the switch and same issue. It is being engaged when my foot is off the gas.

[Elvis]

one of the many repetitions:

is the switch engaged when engine off or also when engine running ?
Vacuum applied to the butterflies with worn shaft/bushings keep the butterflies a bit open.

I had this on 3-4 cars so far, I'm wondering that I am the only one repeating this.


test - at high idle push the butterflies to close all the way. does idle go down ?

fix: more force on the spring around the butterfly shaft/lever.

[Jonathan]

one of the many repetitions:

is the switch engaged when engine off or also when engine running ?
Vacuum applied to the butterflies with worn shaft/bushings keep the butterflies a bit open.

I had this on 3-4 cars so far, I'm wondering that I am the only one repeating this.


test - at high idle push the butterflies to close all the way. does idle go down ?

fix: more force on the spring around the butterfly shaft/lever.

I gotta say Elvis, I for one am pretty glad you took the time repeat this. I followed along and have seen what you described here on my car.

I was working via email with Dave S the last few days so just to recap:

I confirmed my vacuum hose routing is as per the diagram. Everything is going where it should but I'm sure how to access this thermal switch with the three connections. How much more than the air filter housing do you need to remove to get down to it?

With the air filter housing off, I ensured the throttle cable wasn't getting pinched when I put it back on.

My vacuum solenoid behind the fuel distributor is humming/buzzing with the key on and engine off. If I play with the throttle with my finger on the solenoid, I can hear/feel the pitch of the humming change but no noticeable clicking.

I confirmed with my engine off that the throttle lever arm is indeed pressing in on the micro switch when at rest.

But here's the thing, I started up the car, auto trans in park and it's idling nice around 800 RPM. I gave it some gas to rev it up some but it wouldn't settle back to 800. Instead it was around 1,000 RPM. Then sure enough, I walk back and poke my finger in there on the lever arm and what do you know it was not quite engaging the micro switch.

So if I felt it wasn't quite strong or free enough to return to rest with the engine on, how is it I can add some tension to the butterflies spring? Or is just lubing that pivoting axle going to help?

Thanks!

[sdg3205]

Jonathan,

Put me down for another owner who went through this!

I had just done a full VOD rebuild so I had lots of adjustments to make.

In addition to the butterfly springs, the throttle spool should help bring the vavles back to full rest/idle position. Check that the spool has both springs in place and is rotating properly. Apply grease if needed. Then, the length of the arm that attaches to the ball joints of the spool and butterfly vavles can be adjusted (made shorter) by loosening the nuts and turning the arm.

[sdg3205]

Also Jonathan, the thermister under the intake can be reached by touch, albeit difficult. You can verify routing this way but you'd have to remove the intake manifold to replace it. I doubt it is at fault though.

[Jonathan]

Jonathan,

Put me down for another owner who went through this!

I had just done a full VOD rebuild so I had lots of adjustments to make.

In addition to the butterfly springs, the throttle spool should help bring the vavles back to full rest/idle position. Check that the spool has both springs in place and is rotating properly. Apply grease if needed. Then, the length of the arm that attaches to the ball joints of the spool and butterfly vavles can be adjusted (made shorter) by loosening the nuts and turning the arm.

Thanks Dave.

Can I try to grease it without taking it apart? The throttle spool that is? I have never had one apart, so I was just wondering if there was a way to lube it as is. Like squirting throttle body cleaner or some sort of grease in there (perhaps equivalent to something I would use on door latches/hinges)? Same goes I guess for the butterfly valves rotating axle, which I could likely get lubed from above, and then just rotate manually a number of times to work the lube in. Good idea/bad idea?

[DavidProehl]

Jonathan,

Put me down for another owner who went through this!

I had just done a full VOD rebuild so I had lots of adjustments to make.

In addition to the butterfly springs, the throttle spool should help bring the vavles back to full rest/idle position. Check that the spool has both springs in place and is rotating properly. Apply grease if needed. Then, the length of the arm that attaches to the ball joints of the spool and butterfly vavles can be adjusted (made shorter) by loosening the nuts and turning the arm.

This is likely what happened with me. I also did a VOD rebuild fairly recently, likely I need to make a few minor adjustments to get the arm to fully rest on the switch.

[Elvis]

You can try to lube it but it won't work or will only last til the next intersection...

As the two ball joints have some play you can mess with the throttle spool without any success. Been there...try it,
lube it but don't expect too much of it.



Take the butterfly unit out and with a vice and screw driver you should be able to bend the end of the spring a bit to get more force on it.
I can't find a picture at the moment, but I bet once you have it out you'll see what I mean.

I did this about 8-9 years ago. Meanwhile I was in Houston (2005 ?), bought a new butterfly unit just in case...but still use my original one
with the bent spring.

Elvis








I gotta say Elvis, I for one am pretty glad you took the time repeat this. I followed along and have seen what you described here on my car.

I was working via email with Dave S the last few days so just to recap:

I confirmed my vacuum hose routing is as per the diagram. Everything is going where it should but I'm sure how to access this thermal switch with the three connections. How much more than the air filter housing do you need to remove to get down to it?

With the air filter housing off, I ensured the throttle cable wasn't getting pinched when I put it back on.

My vacuum solenoid behind the fuel distributor is humming/buzzing with the key on and engine off. If I play with the throttle with my finger on the solenoid, I can hear/feel the pitch of the humming change but no noticeable clicking.

I confirmed with my engine off that the throttle lever arm is indeed pressing in on the micro switch when at rest.

But here's the thing, I started up the car, auto trans in park and it's idling nice around 800 RPM. I gave it some gas to rev it up some but it wouldn't settle back to 800. Instead it was around 1,000 RPM. Then sure enough, I walk back and poke my finger in there on the lever arm and what do you know it was not quite engaging the micro switch.

So if I felt it wasn't quite strong or free enough to return to rest with the engine on, how is it I can add some tension to the butterflies spring? Or is just lubing that pivoting axle going to help?

Thanks!

[Bitsyncmaster]

It's so common for that last bit of throttle not to close reliably (with the engine at idle). Definitely set your spool spring to the higher notch. John at special T sells an idle switch with less spring force. That was one major issue that made me design my idle ECU to work without the idle switch. But you still need that throttle plate to close reliably.

[sdg3205]

Jonathan and Elvis

I had luck by removing the unit, doing a thorough cleaning and then fully greasing the springs and axle it spins on.

[Bitsyncmaster]

Jonathan and Elvis

I had luck by removing the unit, doing a thorough cleaning and then fully greasing the springs and axle it spins on.

Yes. I had to grease my spring a few years ago.

[Jonathan]

Here's a little update from a good day yesterday troubleshooting and learning about my car. I give a TON of credit to Dave Swingle as we traded quite a number of emails working through this. Thanks Dave.

I was getting the high idle and it was most noticeable while in park on the auto trans. In fact, the car would drive well, but both before and after being in gear, it would tend to spike up to 1,100 or even 2,000 RPM and wouldn't fall back down when you released the gas. I got poking around with the throttle spool and assembly area and would realize that even though the spool was back to it's rest position, it didn't 100% translate to the lever arm being back at the zero position.

I felt the linkage arm underneath almost had a bit of slack in it, so I was able to take it off at the ball and socket joint under the spool, loosen the lock nut, and dial it in one full turn. I greased the moving parts, ball socket, spring, etc. and put it back together. I haven't yet taken apart the butterfly valves axis and lubed it, but I did apply some grease from above (although it might not have been that effective).

Well, that 1 mm or so shortening of the linkage arm really helped. Now I have the car idling right at the 775 RPM area and when you give it gas, it does relax back to the proper spot. Dave also pointed out my spring was up in the "groove" on the end of the rod on the bracket in the spool and that I was missing the 4 snap rings that came with the deice kit. Well, interesting thing to learn, because low and behold those 4 snap rings were in the bottom of a box in a baggie of parts from that deice kit that I didn't know what to do with at the time. They are now installed and keep the end of the spring where it is supposed to be.

I also tried to confirm the wiring connections were good on the micro switch as well while I had the air filter housing off.

We looked at confirming the vacuum hose routing while we were troubleshooting and that identified something else interesting. While my hoses look to all be going where they are supposed to, Dave had me listen for a clicking of the vacuum solenoid while the key was on but engine off and you worked the throttle from behind. No clicking. We were suspicious the solenoid was not working and the test was to warm the engine up and pop off the hose going to the distributor and see if there is vacuum at idle. Yep, there was. So I am getting vacuum through the solenoid at idle which means the solenoid is not doing what it is supposed to do.

I am looking to get a replacement solenoid in there, and then we will review what my ignition timing is doing in case someone before me has adjusted it out of spec to compensate for the bad solenoid. I did hear the engine sound different while I had the hose pulled off at idle. This may mean it runs different even at speed, with possibly bad performance and or bad fuel mileage. I'm not sure of all the implications of the timing as I don't have a lot of information on that yet.

Good day overall with the car and learned quite a bit. Funny too as I had sort of forgotten that this past Tuesday was my 5 year anniversary of buying 3937 :)

[sdg3205]

Great progress, Jonathan.

[Dangermouse]

Great job!

Could you post a pic of where those snap rings went. I don't think I ever installed mine either.

[DMCMW Dave]

Great job!

Could you post a pic of where those snap rings went. I don't think I ever installed mine either.

Center of this photo. They snap over the post that the spring rests on. Also a bit of grease on the end of the spring is a good idea.

12747

[82DMC12]

I recently fixed up a car with this exact problem. Starts perfect at 750rpm, then after a couple of intersections it would be around 1000. It turned out the outer throttle spring was binding on itself slightly, even though it was well greased. I got the spring to sit slightly at an angle on the rotating part and that did the trick. It's like the spring was trying to get a coil up and inside the adjacent coil.

Andy

[DavidProehl]

Well, that 1 mm or so shortening of the linkage arm really helped. Now I have the car idling right at the 775 RPM area and when you give it gas, it does relax back to the proper spot.


Did this tonight as well on my linkage and now it idles properly as well. Amazing what that 1 mm can do!

[David T]

When working on a problem like this one you will find it is never "just" one thing. It is usually a couple to a bunch of little things that all add up. After 30 years the grease in the throttle spool is hard and gritty. The whole assembly should be taken apart, cleaned and greased. Although moving the spring a notch may work I dislike doing that. It can make it tiring holding down the gas pedal on long drives. Much better to make the quadrant link just a bit longer so it pushes the throttle arm all the way to idle. The only disadvantage there is there will be a little bit of lost motion as you depress the gas pedal. You should also lubricate the throttle cable with anti-freeze. Who knows if it was ever done and if it was it was over 25 years ago! We should add lubricating the quadrant ends to the lubrication maintenance schedule. BTW the link is a left-right hand adjustment like a turnbuckle so you can adjust it very precisely. It also has those tiny clips like on the struts so you MUST remove them before trying to remove the socket ends. Make sure the vacuum hoses are on the correct ports of the solenoid valve. It matters. If you do it the wrong way you do not release the vacuum on the distributor and leak vacuum from the intake. Very easy to verify with a timing light. Also a good check on the mechanical advance. If they are not working right you can overheat the motor and have lousey gas mileage.
David Teitelbaum

[Kevin]

I also just started having this EXACT problem where the lever arm isn't quite going all the way back down. Glad I have a whole thread of things to try, thanks all!

[Elvis]

Gentlemen, I am curious if this fixed you problem permanently or if it still does idle to high
every once and then.
As I went thru all this for a pretty long time where I tried, tested, cleaned, lubed again and again
I gave the spring a little more kick.

NOTE !!!! This only applies if the butterflies do not fully close under vacuum (engine running) but
do close completely when the engine is off !!!! Also you have to make sure the cables and springs
move easily, are cleand and lubed and adjusted properly !!!!


This is the butterfly return spring untouched. If you say - hey it's not really clean and super lubed
then I say - this is the third car where I had this problem and started with the known working solution.
(but I also cleand and lubed it afterwards. it's a bit easier to bend the spring without lubricant on it)
12957


And this is how I bent it to get more torque to close the plates.
12958

Since then my idle NEVER stayed high again. Not even when very hot and in traffic at an intersection
where you push the gas just just very slightly. No, never again - but that happened every once and
then by just doing the things mentioned in the posts before.
The new butterfly unit I bought 8 years ago is still unused in the box.
On your gas pedal this stronger spring makes no noticeable difference.


I also found it can be helpful to install the switch a bit higher to reduce the force of the switch that also
can keep the butterflies open. The two nuts I used were drilled thru, they just gave me 5-6mm more hight.
Quickly done, quickly undone and costs nothing:
12959


Hope this is of help,
Elvis & 6548 ( ~8 years with that modified spring)

[DavidProehl]

Elvis - My idle is still running where it needs to be, no change. Still, I like your modification and can't help but think this is a better solve than lengthening the throttle linkage rod. That looks like the way to go. Did you remove your butterfly unit to make this change? Seems like it would be difficult to get to otherwise. Wish I would have known about this fix when I had this all apart last winter for my VOD cleaning.