Decel valve springs: replaceable?

[Morpheus]

GM everyone,

After putting my top end back together, I started it for the first time in 2 1/2 months last night.

After a few initial stumbles, the car roared to life and would not settle below 2000 RPM. I adjusted the linkage and actually held the throttle all the way closed and it had no effect. I seem to recall that when I had my throttle body apart for cleaning, the decel springs appeared to be like this picture:
39444
(not my actual springs, but they look like this)

My question is this: Since new throttle bodies appear to be NLA, is there a way to replace these springs? If so, where would one acquire them? If not, is there some other solution? Can the springs be reconditioned?

I know high idle threads are plenty here, and believe me I searched for several hours for the answer to no avail.

[Bitsyncmaster]

If your springs look like that photo, they are NG. I don't think anyone has documented a replacement. You could measure some good springs and maybe use that data to find replacements. Or you could setup a test set to measure the opening of some replacement springs. My guess would be they open around 20 inchs/mg.

[Horsebox]

I can't really help you with your question but the guy in this blog replaced his entire throttle body for NOS, which brought his high idle down somewhat but not all the way...

http://delorean6575revisited.blogspot.co.uk/2013/02/installing-new-butterfly-assembly.html

Have you gone for the low hanging fruit first? Such as microswitch connections, does the switch work electrically, does the screw actually trip the microswitch when the throttle is closed, does the idle motor get +12V, have any of the three pins in the connector on the idle motor backed out?

Sorry if that's not what you're looking for!

[Morpheus]

I was able to actually improve the idle quite a bit by adjusting the linkage and such. I'm bleeding the coolant system now, so after it cools off i'll check it again.

Unless someone knows of another source for throttle bodies, i guess i'm stuck. Best part, while tightening the 3 brass screws, I broke the head of one off. It's down tight, so I'm hoping it will hold.

[Bitsyncmaster]

I had bad deceleration springs and what would happen is with the curb idle all the way off, it would run about 1,000 RPM with a hot engine. It would hold 775 RPM until it warmed up. But with that curb idle all the way off the idle would undershoot to about 500 RPM when you took your foot off the throttle.

[Morpheus]

THat's exactly what mine does right now.

Start it up, it runs about 775 or so (haven't hooked up my dwell meter to verify, but it sounds normal and it's below 1000), then when it's hot it won't stay below 1000 - 1200.

[Delorean Industries]

I can hook you up with a good throttle butterfly and replacement brass screw. We have a surplus of good refurbished ones.

[Morpheus]

I'm very interested, Josh! What's the damage going to be?


Sent from my iPhone using Tapatalk

[DMCVegas]

THat's exactly what mine does right now.

Start it up, it runs about 775 or so (haven't hooked up my dwell meter to verify, but it sounds normal and it's below 1000), then when it's hot it won't stay below 1000 - 1200.

Lengthen the striker screw for the Idle Speed Microswitch, and then bend the bracket UP to engage quicker. You'll watch for RPMs drop at a slower rate.

[Morpheus]

Robert, how will that fix the springs on the butterflies?

[Delorean Industries]

25.00 shipped Brandon. Just let me know which screw you need. Slotted or not.

[DMCVegas]

Robert, how will that fix the springs on the butterflies?

Excellent question. BUT, I'll warn you that this isn't going to be a quick post. Though I will keep it as lean and to the point as possible.

So, the entire point of the Deceleration Valves (which is what those spring valves on the throttle plates are called) is strictly to maintain emissions. Tool lean of a mixture, you get high Nitrous Oxide (NO1 & NO2, aka NOx), and too rich and you get high Hydrocarbons (HC) which is just unburned fuel. So when you're going from a higher RPM down to idle, your butterflies will snap shut. This will cause a vacuum spike in the intake manifold between the butterflies and the intake valves. That results in a lean condition, and spikes your tailpipe emissions. So the idea behind those Deceleration Springs is that the vacuum will pull them open, and feed extra air into the manifold to reduce the lean condition and keep it as close to 14.7 as possible... Until the Idle Speed Circuit kicks in.

Why?

Well, our flavor of K-Jetronic is a bit of a different beast when it comes Idle Speeds. Earlier versions of K-Jet actually used those 3 idle speed screws to set, balance, and maintain the idle, with an Auxiliary Air Valve to feed additional air during cold engine conditions, and while air conditioning was running to up or maintain RPMs respectively. But, the thing is this: The basic Idle Speed Circuit with those screws was constantly running. Deceleration Valves were NOT needed, because the additional air would just get sucked in through the Idle Speed passages, just like any carbureted engine.

With our K-Jetronic, that is NOT so. BOSCH decided to hand over complete idle control over to a separate electronic controller that could adjust the RPMs to specifically whatever it wanted, regardless of load. But, here is the catch: It only turns on when the Microswitch is depressed. So in order for the engine to have more precise mechanical control over itself, it the electronic Idle Speed Circuit will completely disable when the vehicle is NOT idling. So the ideal is that when you let off the pedal and the engine suddenly becomes starves of oxygen, the Idle Speed Circuit will automatically engage and take over it's responsibilities.

The problem however is that at the factory, that striker screw was set to just barely trip the Microswitch when the butterflies were closed. So even after only 20 years I found that there was enough dirt and possible corrosion inside the switch that created such extra resistance on the spring, that unless I violently snapped the throttle back into it's rest position instead of gently lifting my foot of the gas pedal, I couldn't even get the circuit to engage. So I adjusted the linkage to avoid all of that buy giving the striker extra leverage, and got the circuit to turn on earlier.

Before, my engine speed would plummet to about 500 RPMs, and I'd have a 50/50 chance of the thing dying. Plus it made shifts a whole lot more difficult. But after I did the change, my RPMs would gently float down like a modern car, and I'd never have a problem with dying, or low voltage issues.

Now, even more to the point about those springs is the fact that you've also got the LAMBDA system in there too trying to correct things. Too lean of a mixture because your Deceleration Valves are stuck, and LAMBDA is going to enrich your fuel injectors. Then as your idle balances out, now your engine is too rich! So LAMBDA starts to lean things out and starves your engine of fuel to balance things out. Which BTW can affect engine speeds. Because if LAMBDA sees lean and pumps a bunch of fuel in and now your idle speed has dropped way too low, the Idle Speed Motor opens up to try and increase speed by feeding more oxygen, and thenyour engine speed will surge by itself and further cause problems because it's being feed fuel and oxygen that you. So now the idle speed motor will snap closed to lower RPMs and create another plummet. But adjusting the linkage avoids all of this.

The Deceleration Valves can cause problems, but you can even remove them without any consequences, save for a slight hit on emissions for a brief second or two. The problem I'm wagering that you're having is that because of a Microswitch with a now higher unsprung resistance, your Idle Speed Circuit isn't engaging on time, if at all in some cases. That's what is causing your low idle.


P.S.
Turbocharges cars naturally place their turbos BEFORE the butterflies because of that vacuum problem I mentioned. The BAE single and Island Twin turbo charging kits both placed their compressors between the Intake Valves and the Butterflies, right in that vacuum area. Turbos are designed for pressure, NOT vacuum. So as a result the vacuum will damage the cartridge seals and cause an oil leak. That is why turbo charged DeLoreans will typically give a puff of smoke when starting, and why so many people think that the engines in them are bad. They're not. It's just a unique problem for the DeLorean because of poorly thought out aftermarket designs. Because if you notice, the Legend Turbo cars had totally different plumbing to avoid this problem.

[Morpheus]

25.00 shipped Brandon. Just let me know which screw you need. Slotted or not.

I need a whole butterfly assembly Josh! Unless you have a way to just replace the decel springs.

[Bitsyncmaster]

I seem to remember the idle switch does not disable the function of the idle control unit when I first started designing my own idle ECU. I will try to test another stock ECU on the next core I get returned. I don't have any cores not updated with my circuit board now.

The idle switch is hardwired to turn the advance solenoid on and off. It also feeds the ECU through a diode. Not sure why they used that diode. I guess the ECU is using 5 volt logic so the diode would prevent driving 12 volts into the ECU. The diode would also prevent inductive voltage spikes produced by the advance solenoid turning off.

[FABombjoy]

So as a result the vacuum will damage the cartridge seals and cause an oil leak. That is why turbo charged DeLoreans will typically give a puff of smoke when starting, and why so many people think that the engines in them are bad.
I apologize as this is tangential to the topic, but I just spent a few months working out my own BAE-like single T3 turbo setup and learned quite a bit regarding this through experimentation. Specifically dealing with oil smoke cloud at startup of which I was able to completely resolve my issues. The lessons learned were:

1: Draw-through turbos must have a positive oil seal, also called a carbon seal. A dynamic seal will cause oil consumption.

2: Where applicable, carbon seal must be installed 100% correctly. There are ways to build/rebuild a turbo even with this style of seal and have it still not work correctly in draw-through. This was my #1 problem as the rebuilder failed in this regard.

3: The oil drain location(s) specified by Island & BAE may be borderline for drainage depending on oil feed pressure, which could cause oil to build up in the center section that pushes into the compressor and exhaust housings. I'm speculating a bit here as I don't know what, if any restrictors were in place or built in to the IHI or Rajay turbos. I know that RHB5s were available with dynamic seals and were retrofittable to carbon, but still it would need to be done properly to prevent oil from making its way in. I measured feed pressures using a few different restrictors and found that these engines can really drown a turbo in oil. Even a .035" restriction orifice when fed directly from the galley plug via AN4 feed line will approach 40PSI cold / 10PSI warm at the turbo - at idle RPM! For a journal bearing T3 turbo that's considered adequate.

In the end I took a page from Porsche's playbook and built a vented drip tank to provide overflow relief if needed. It would now taken an extraordinary event to have oil back up into the center section.

4: The PCV setup is mediocre for an N/A car. Without modification a BAE/Island setup will not evac the crankcase very well, possibly leading to oil backup.

There were factory draw-through cars, even with catalytic converters, so oil burning doesn't have to be a way of life :)

Thread relevant: I'm running my draw-thru turbo car with the decel valves removed. The intake / compressor side sees about 25in/hg if you go into boost and close the throttle. I have a plan to utilize the IAC valve under those conditions to provide some relief and lessen the lean spike.

Dave - If you can build me one of your IAC controllers with a falling-edge trigger, let me know!

[Elvis]

Dave is right and I wrote it like 10..15 times so far. The micro switch does NOT turn the idle ECU off !

Instead it set's the idle to a higher rpm when depressed.

BUT

if the rpm is higher than thaht set speed (somewhere above 1000rpm) the idle valve will close as far as it can.

BUT

who know a little bit somethng about control loops knows P, I and D.
there is a "D" - "Differential" - circuit that will also open the idle valve when the rpm is dropping too fast.

just some little facts for the evening...

Elvis & 6548

[Morpheus]

Excellent question. BUT, I'll warn you that this isn't going to be a quick post. Though I will keep it as lean and to the point as possible.

So, the entire point of the Deceleration Valves (which is what those spring valves on the throttle plates are called) is strictly to maintain emissions. Tool lean of a mixture, you get high Nitrous Oxide (NO1 & NO2, aka NOx), and too rich and you get high Hydrocarbons (HC) which is just unburned fuel. So when you're going from a higher RPM down to idle, your butterflies will snap shut. This will cause a vacuum spike in the intake manifold between the butterflies and the intake valves. That results in a lean condition, and spikes your tailpipe emissions. So the idea behind those Deceleration Springs is that the vacuum will pull them open, and feed extra air into the manifold to reduce the lean condition and keep it as close to 14.7 as possible... Until the Idle Speed Circuit kicks in.

Why?

Well, our flavor of K-Jetronic is a bit of a different beast when it comes Idle Speeds. Earlier versions of K-Jet actually used those 3 idle speed screws to set, balance, and maintain the idle, with an Auxiliary Air Valve to feed additional air during cold engine conditions, and while air conditioning was running to up or maintain RPMs respectively. But, the thing is this: The basic Idle Speed Circuit with those screws was constantly running. Deceleration Valves were NOT needed, because the additional air would just get sucked in through the Idle Speed passages, just like any carbureted engine.

With our K-Jetronic, that is NOT so. BOSCH decided to hand over complete idle control over to a separate electronic controller that could adjust the RPMs to specifically whatever it wanted, regardless of load. But, here is the catch: It only turns on when the Microswitch is depressed. So in order for the engine to have more precise mechanical control over itself, it the electronic Idle Speed Circuit will completely disable when the vehicle is NOT idling. So the ideal is that when you let off the pedal and the engine suddenly becomes starves of oxygen, the Idle Speed Circuit will automatically engage and take over it's responsibilities.

The problem however is that at the factory, that striker screw was set to just barely trip the Microswitch when the butterflies were closed. So even after only 20 years I found that there was enough dirt and possible corrosion inside the switch that created such extra resistance on the spring, that unless I violently snapped the throttle back into it's rest position instead of gently lifting my foot of the gas pedal, I couldn't even get the circuit to engage. So I adjusted the linkage to avoid all of that buy giving the striker extra leverage, and got the circuit to turn on earlier.

Before, my engine speed would plummet to about 500 RPMs, and I'd have a 50/50 chance of the thing dying. Plus it made shifts a whole lot more difficult. But after I did the change, my RPMs would gently float down like a modern car, and I'd never have a problem with dying, or low voltage issues.

Now, even more to the point about those springs is the fact that you've also got the LAMBDA system in there too trying to correct things. Too lean of a mixture because your Deceleration Valves are stuck, and LAMBDA is going to enrich your fuel injectors. Then as your idle balances out, now your engine is too rich! So LAMBDA starts to lean things out and starves your engine of fuel to balance things out. Which BTW can affect engine speeds. Because if LAMBDA sees lean and pumps a bunch of fuel in and now your idle speed has dropped way too low, the Idle Speed Motor opens up to try and increase speed by feeding more oxygen, and thenyour engine speed will surge by itself and further cause problems because it's being feed fuel and oxygen that you. So now the idle speed motor will snap closed to lower RPMs and create another plummet. But adjusting the linkage avoids all of this.

The Deceleration Valves can cause problems, but you can even remove them without any consequences, save for a slight hit on emissions for a brief second or two. The problem I'm wagering that you're having is that because of a Microswitch with a now higher unsprung resistance, your Idle Speed Circuit isn't engaging on time, if at all in some cases. That's what is causing your low idle.


P.S.
Turbocharges cars naturally place their turbos BEFORE the butterflies because of that vacuum problem I mentioned. The BAE single and Island Twin turbo charging kits both placed their compressors between the Intake Valves and the Butterflies, right in that vacuum area. Turbos are designed for pressure, NOT vacuum. So as a result the vacuum will damage the cartridge seals and cause an oil leak. That is why turbo charged DeLoreans will typically give a puff of smoke when starting, and why so many people think that the engines in them are bad. They're not. It's just a unique problem for the DeLorean because of poorly thought out aftermarket designs. Because if you notice, the Legend Turbo cars had totally different plumbing to avoid this problem.


Wow, thanks for that wealth of information! Actually, the problem is what Dave described in that it idles somewhat normally until warmed up, and then will not drop below 1000 no matter what I do. Sometimes, I have surging, which is probably the Lambda fighting the Idle speed computer. I actually have the microswitch set to engage well before the bottom pin, which is backed out beyond the point where the butterflies are fully closed... it just barely touches the striker plate.

[DMCVegas]

I seem to remember the idle switch does not disable the function of the idle control unit when I first started designing my own idle ECU. I will try to test another stock ECU on the next core I get returned. I don't have any cores not updated with my circuit board now.

The idle switch is hardwired to turn the advance solenoid on and off. It also feeds the ECU through a diode. Not sure why they used that diode. I guess the ECU is using 5 volt logic so the diode would prevent driving 12 volts into the ECU. The diode would also prevent inductive voltage spikes produced by the advance solenoid turning off.

I may be wrong on that then. I'm basing this off of what my observations were with my own car. I'd drop down to 500 RPMs after higher RPMs. And I do mean drop. It would just plummet. BUT, if I had the striker engage earlier, then it would allow the RPMs to gently float down at a slower rate to settle in with no surging to it's idle speed.

But absolutely with that LAMBDA operating independently, it will cause the idle to surge from vacuum leaks and bad Deceleration Valves.

[Bitsyncmaster]

I may be wrong on that then. I'm basing this off of what my observations were with my own car. I'd drop down to 500 RPMs after higher RPMs. And I do mean drop. It would just plummet. BUT, if I had the striker engage earlier, then it would allow the RPMs to gently float down at a slower rate to settle in with no surging to it's idle speed.

But absolutely with that LAMBDA operating independently, it will cause the idle to surge from vacuum leaks and bad Deceleration Valves.

When the idle switch is engaged earlier, it would remove the advance. I would think that would cause idle to drop quicker. You may be correct the switch has something that changes how the idle ECU works.

Yes the Lambda does cause idle RPM changes. it's one of the main reasons some engines get idle hunt.

[DMCVegas]

When the idle switch is engaged earlier, it would remove the advance. I would think that would cause idle to drop quicker. You may be correct the switch has something that changes how the idle ECU works.

Yes the Lambda does cause idle RPM changes. it's one of the main reasons some engines get idle hunt.

Rev your engine up to like 3,500 or so RPMs, and then just turn the engine off at the ignition switch. The RPMs will just go into freefall. That is *exactly* how my engine always acted. Every single time without fail whenever I let my foot off of the accelerator pedal. What was worse was if I was creeping along like in a parking lot or a situation like that were I'd only need to slightly press the pedal and would just gently let off the pedal.

The spring on the Idle Speed Microswitch was stiff enough that it would actually hold the entire linkage up, and keep from ever tripping the the switch at all. Everytime that happened, the engine would die without fail. Whomever set that linkage at the factory tried to do so to where the striker screw would just barely touch the Microswitch, and only enough to trigger it. When the Microswitch spring gets that stiff over time due to dirt and has more resistance, the Throttle Spool Spring having now been gently unsprung, doesn't have enough leverage to push the Microswitch down in that position. Not unless you slap the gas pedal and make the entire linkage slam back down into it's resting position.

So, by extending the striker screw, and bending the bracket up to where the switch gets engaged sooner, and in the rest position is almost all the way down (to ensure that the throttle isn't resting on it), the linkage has MUCH more leverage and trips that switch every time.

Like I say, on my engine, the RPMs just float down gently now, and I stopped having and deceleration problems to where the RPMs would drop down to 500, and the engine was too low to idle with a load, and it was too late for the ISM to crack open and catch it.

[Bitsyncmaster]

That idle switch is a pain. That is why I removed it and let my idle ECU control the advance solenoid.

[DMCVegas]

The linkage itself can certainly be a pain. Like I said before, I've heard that the throttle linkage was never properly adjusted in Douvrin before the engines got shipped off to Belfast for installation...which results in engines that can never go full WOT. And while I've no idea if that's true, I have seen it on my car, and another were it was REALLY bad.

On mine I had to adjust the connecting rod between the throttle spool and the lever that controls the butterfly valves. I spun the sockets on the end to remove all slack to the point where I preloaded it. Much better throttle response after that since as soon as the spool rotated it immediately acted upon the lever.

The worst par is that WOT Microswitch for the LAMBDA to enrich the mixture. That damn thing almost killed me! I was driving into work one morning, and my throttle locked up and the car was accelerating out of control. Luckily I had a 5-Speed, so I hit the clutch and stopped by the side of the road. Turns out there there's a little plate that the screws attach to, in order to secure the switch to the bracket. My screws were loose enough to where one came out, and the Securing Bracket rotated around and locked my Throttle Spool by wedging it about halfway open. Luckily it was just a quick fix and I was on my way in less than 10 minutes, but that could easily have caused a wreck.

[Morpheus]

The WOT switch is another story. I am trying to figure out how to adjust it so the spool actually makes contact with it. I adjusted the pedal travel as much as I could, and adjusted the switch position as well, but when I put it to the floor it's not enough to hit the switch.

[Elvis]

Clermont, FL ? east of Orlando ?
Do you know Jordan ?

[DMCVegas]

The WOT switch is another story. I am trying to figure out how to adjust it so the spool actually makes contact with it. I adjusted the pedal travel as much as I could, and adjusted the switch position as well, but when I put it to the floor it's not enough to hit the switch.

That should probably be split off into another thread. But the big question is what is stopping the travel of the Spool before it makes contact? It would be one of 2 things:


Too much slack in the Throttle Cable.
Too much slack in the Linkage Rod.

[Morpheus]

Clermont, FL ? east of Orlando ?
Do you know Jordan ?

Yes I do.

[Elvis]

That should probably be split off into another thread. But the big question is what is stopping the travel of the Spool before it makes contact? It would be one of 2 things:


Too much slack in the Throttle Cable.
Too much slack in the Linkage Rod.



vakuum - as already mentioned felt 2000 times

easily to test with engine off and then with engine on.
I had this on 3 of 3 cars - so why would others not have the same problem?


so simple to test

[DMCVegas]

vakuum - as already mentioned felt 2000 times

easily to test with engine off and then with engine on.
I had this on 3 of 3 cars - so why would others not have the same problem?


so simple to test

On the WOT microswitch for the LAMBDA circuit?

[Morpheus]

In keeping with the original subject matter, I wanted to show you all what my springs look like. I took my throttle body off in advance of receiving some good butterflies from Josh @ DPI and this is what I found:

39522

[opethmike]

Oh look Elvis is being a self-important douche. That's new.

[Bitsyncmaster]

In keeping with the original subject matter, I wanted to show you all what my springs look like. I took my throttle body off in advance of receiving some good butterflies from Josh @ DPI and this is what I found:

39522

So far, all the good ones I have seen have the springs evenly spaced and all the bad ones look like yours.

[Morpheus]

Update:

Here's a side by side of my old butterflies and new:

3973039731

I'm happy to report that my car now idles as it should. Thanks to Josh @ DPI for getting me the parts I needed to make this happen!

[David T]

Update:

Here's a side by side of my old butterflies and new:

3973039731

I'm happy to report that my car now idles as it should. Thanks to Josh @ DPI for getting me the parts I needed to make this happen!

Those valves are only important on the 5-speeds. For automatics they can be sealed shut. On one car I worked on that had a custom exhaust we experimented with different springs to modify the exhaust note on decel. It did make a difference. I found the springs inside ball point pens to be a close fit with some modification. I think the cars that had problems with leaking decel valves must have had earlier problems with backfires and the heat damaged the springs. Once the springs got hot they lost their tension and could not hold the valves shut tightly. Leaky decel valves have the effect of bypassing the idle motor and increasing the idle speed.

[Delorean Industries]

Huh David?

[Bitsyncmaster]

I found the springs inside ball point pens to be a close fit with some modification.

?

[David T]

During the experimentation we tried cutting and stretching the original springs and eventually ruined them. In desperation we tried other springs and the small spring in a retractable ball point pen are close enough in size that we were able to use them in place of the originals. I did shorten them so they would fit. We did not have a set of replacement springs on hand so we improvised.