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Walter Moore

Throttle opener control system?

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This may not be the right forum for this question, and those of you outside of North America likely don't know what I am talking about, but there is a device on my intake manifold that the Haynes manual labels a " Throttle opener control system".

I assume from the description of the function that this an emission control system. Does it perform any other important function?

The reason that I ask, is this system connects to the linkage for the carbs via a sleeved lever that actuates the linkage near the front carb, and this sleeve is rusted in place. With the throttle opener connected, the throttle is jammed.

I am re-building the engine (step 1 of re-building the car...) and if I don't need this vacuum operated menance I would prefer not to re-install it. From the manual I gather that it's purpose is to prevent dumping excessive unburnt fuel out the exaust pipe when shifting gears. On the otherhand, I am not impressed with the idea of having something on the car that holds the throttle open for 5 seconds after I let off the pedal...

The Haynes manual claims that this system was installed only on the 260Z, but my car is a 1971 240Z, with an L24 engine and 4 screw round top carbs, and it clearly has all the hardware, except the solenoid to disable the system when the car is moving less than 10 MPH. ( No wire from the speedometer...)

I guess the book is wrong.

We don't have emissions testing here in Indiana, and even if we did, I think that pre-1975 cars are generally exempt outside of California, so if it won't hurt the car any I am not going to re-install this when I put the thing back together.

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Are you possibly talking about the Anti-Backfire Valve fitted for emissions reasons? If so, it came on most 240Z's. It's purpose is to momentarily (VERY momentarily, nowhere near 5 seconds!) keep the throttle open to minimize the dumping of excess raw fuel into the engine when shifting gears, etc.

On the other hand, maybe it is a 260Z emissions deal, and was left in place when someone replaced the 240Z intake manifold with an N36 (or is it N33) 260Z Intake. The 240Z should have and E88 intake unless it is a VERY early (70 or early 71 model) mfg car.

Can you upload a picture of what you have? That would help folks to identify it for you.

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Hi Walter, Glad to hear you got the hatch open.The throttle opener was suppose to act as a dampener when you let off the gas.They were to stop the carbs from reducing the fuel amount too fast.Although they were on all 73,s.I think I read somewhere that they were really intended for autotransmission cars.Regardless trash it.You will never miss it. Have fun!! Daniel

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The intake has the part number "E46" cast into it, so I am sure it doesn't belong to a 260Z...

The 5 seconds I refered to is the time the Haynes manual claims the system should take to bring the idle speed back to normal after letting off the throttle, but that may only apply to the 260Z version with the electrical signal from the speedometer.

If I understand the operation correctly, it would prevent backfiring, at least in theory. In any event, I think that I will just park the "throttle opener" somewhere as a decoration and get on with the restoration.

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I have a '72 with the throttle opener still installed. I wanted to get it working as I was hoping it would help with popping and low idle speed when hot etc. Mine was frozen so I took the vacuum control valve apart, used some Kroil to loosen the adjustment screws and put it back together. At first it appeared to do the trick and I was able to adjust so that it would actuate the valve when I released the throttle. The problem is that when driving, it oscillates rather than just opening the valve for a few seconds (holding the throttle open slightly) and closing. Strange because when I checked the manifold with a vacuum gauge it was steady.

Here are some photos of the device disassembled. There was foam between the orange diaphragm and the adjustment spring plate - it had disintegrated and with no suitable replacement I left it out upon reassembly.

There are many posts on this that recommend removing it or disabling it but I am looking to find someone who actually got theirs working correctly?

post-1378-14150816131001_thumb.jpg

post-1378-14150816131622_thumb.jpg

post-1378-14150816132143_thumb.jpg

post-1378-14150816132583_thumb.jpg

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Mine works as intended, but it should as it has never been monkeyed with. It will reduce popping in the initial off-throttle condition, but I found it to be annoying to have the RPM hang there between shifts and such, and so I backed off the adjustment nut to disable it. It still works normally, but doesn't quite touch the throttle linkage.

post-8596-14150816133037_thumb.jpg

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Similar to what Arne has done, I've adjusted my throttle damper screw to be about 1/8" away from touching the plate on the linkage. It keeps it from operating under normal driving conditions, but does engage to some extent when I'm driving a bit more aggresively.

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Is there a hole in the side of that thing to vent to atmosphere for when it is not holding the throttle open?

I've got a 74 260 and the throttle opener is a little more complicated because it includes an electronically actuated purge vent.

My first thought on your oscillation is maybe the foam was a damper for the spring? How fast does it oscillate? Does it "hunt" or "buzz"?

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Is the Servo Diaphragm (#4 above) supposed to hold vacuum? Mine isn't so I'm contemplating just pulling the whole thing off. Any suggestions?

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Jarvo2, I saw your other post about this and was going to post there, but I didn't because I don't know for sure.

Somewhere, somehow, there has to be a way for the vacuum which feeds that actuator to bleed off when the system is not actuated, and I don't know where that vent is. In other words, when the manifold vacuum is not high enough that the actuator is pulling on the throttle linkage, then the back side of that actuator #4 should be near atmospheric pressure, and I'm not clear where the port is that assures that.

I asked a while ago above in this thread if that bleed off venting was done in the vacuum control valve, and never heard an answer.

So all I can tell you is I believe there needs to be a bleed in that system somewhere, but I don't know where it is. They could have put a bleed vent into the control valve #2, or they may have designed the actuator #4 to be leaky on purpose. I don't know.

If I designed it, the bleed vent would be in the control valve and the actuator would hold vacuum. Doesn't mean squat though, since I didn't design it.:)

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I know this is an old topic but does anyone know if the bellows screws out or is it a slip fit just held in by the set screw?

My set screw broke so I had to drill it out but the bellows is still stuck. I don't want to ruin the bellows.

Edited by SurferD

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It is a slip fit. Try to hammer it lightly from outside. Maybe heating and then cooling will release it.

Edited by BlueZee
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That was a great explanation thanks!

The crimp on the aluminum ring failed but I was able to tap the brass out. I'll drill/tap the ring to M6x1.0 and use a new set screw and restake it in the steel barrel.  The bellows shaft was really corroded so after cleaning/lube it will work fine. I also got the main part taken apart like the pics above and it's now free to rotate if adjustment is needed. Looks like both diaphragms are in decent shape after 50 years.

Edited by SurferD

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I don't have that upper part. My FSM has the same picture but it's not as crisp. The barrel actually deformed when the brass shaft was hammered out. So I took a washer the exact ID size and a long socket and put it in the vise and viola' back to stock shape. I did get a backup on eBay in case this one fails. I did learn however from carpartsmanual there were different units for automatic/standard transmissions and years. Mine is stamped 66P15.

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45 minutes ago, SurferD said:

I don't have that upper part.

They started with that upper part in 73. Prior years didn't have that.

It's a solenoid valve that they use to disable the opener system when the car isn't moving. In other words... When you blip the throttle at idle sitting still, it won't let the opener pull on the linkage.

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Haha yea if you say something with enough confidence no one doubts you. 
I’m always learning something about these cars. 

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On 11/24/2012 at 3:48 AM, Captain Obvious said:

..They could have put a bleed vent into the control valve #2..

@Captain Obvious : Isn't it a bleeding hole that you were thinking about, in 2012?

Bleeding_Hole.jpg

Edited by BlueZee

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@BlueZee, Thanks for that pic!

Kinda hard to tell for sure, but yes, that may be a bleed hole. if it is, it would be an answer to something that has bothered me for years.

Does that hole actually go anywhere, or is it just a dent from the locking setscrew? Can you pass air through that hole?

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