Captain Obvious

I hope you can get the screw stub out of the throttle shaft. The threads on the original screws are purposely deformed at the tips after the initial installation. This is so they don't accidently come loose and get sucked down your carb throat. You can usually get them out, but they can be a little tough to get started correctly to reinstall unless you clean up the threads a little. Sounds like you cross threaded it... Might not be good. And about my dimensions above... I want to point out that I'm operating in a non-professional shop with uncalibrated measuring tools. Because of that, my measurements could be off a couple thousandths from what you would get with your measuring tools. My RELATIVE measurements were spot on, but the absolutes could be off some. By that, I mean... I cut all of my grooves spot on at .063 wide and .286 across at the narrowest point. I know that because I used the same measuring device for all the work. But in your shop with your tools, you might measure .064 wide and .285 deep. Or something else the other direction. The point is... Use my uncalibrated absolute measurements above as a guide only for getting close, but determine the last couple thousandths in either direction with a test piece and trial-n-error in your shop with your measuring tools.

I edited the info into the above post, but that doesn't bump the thread. So I'm bumping now it so you know I've been back.

Yeah, and that's why I added the thoughts about the fact that it COULD cause a vacuum leak if the holes are in the right (wrong?) spot. I don't think it would take much of a leak to have a significant impact on idle mixture. Wouldn't make nearly as much difference once your foot was on the pedal, but at idle you really need every air molecule going through the AFM. Good luck and here's hoping for the best! PS - I had a dash cap and I took it off. I'd rather look at the cracks than deal with the cap. I know others feel the opposite, but that's just me.

On edit, I just took out a whole bunch of stuff that you knew already... Teach me to read page two without thoroughly reading page one first. Sorry. Carry on. And what Blue said about that spray bar... That rear block isn't long for this world. Looks to me like the tip of that rear tube has already contacted the lobe. Looks like there is a clean spot wear mark on the corner of the tube closest to lobe #12? PS - I don't like your stamped fuel pump. I know you don't either. Just cosmetic, but I prefer the vintage look.

I used 10mm OD Viton O-rings with a 1.5mm cross section and I got them from McMaster - P/N 9263K295. I do have some spares so if you're interested, shoot me a PM. Listed O-ring dimensions are often nominal or "as installed", so before I cut my grooves, I measured the O-rings to be: .401OD .281 ID .060 cross section With that info and a little trial and error, I cut my grooves to be .286 deep and .063 wide. I also checked the size of the throttle plate screws. They are brass screws M4 x 0.70 x 10 mm long (approx.) and they're thread deformed at the tips for retention. I'm guessing that's why one of yours snapped off? Did you get a half turn or so before it locked up or did it snap right away just from crud in the threads?

I was thinking about this a little more and wanted to talk some about the BCDD's impact on mixture and bring up one other additional thought. If the rubber diaphragms inside the BCDD are in good shape then the BCDD won't have any impact on mixture. However, I can imagine a scenario where there could be holes in one or more of those diaphragms which COULD affect mixture ratio. So to modify what I said up above a little... The BCDD doesn't normally have any impact on mixture ratio, but I can imagine a scenario where there could be holes in diaphragms whereby the BCDD draw outside unmetered air into the intake manifold which CAN affect mixture. What you said above about the BCDD's job to introduce extra air into the intake is correct. But an important detail is that extra air is supposed to have gone through the AFM first. If it goes around the AFM and leaks in past one of the diaphragms, then it's a problem. Mine was leaking internally (which doesn't affect mixture), If yours is leaking EXTERNALLY, then you WILL mess with the mixture. And you don't have to remove the solenoid to test it. You can do this: Disconnect the BCDD at the bullet connector. Turn the ignition key to RUN but don't start the car. Walk around to the engine compartment and connect the BCDD bullet. You should hear a distinct "CLICK" from the BCDD when you connect it. Connect and disconnect the BCDD a couple times and verify that it clicks immediately and there's no delay caused by sticky buildup inside. Or if you'd really rather... it's very easy to pull the solenoid off the BCDD and test it on a bench. Just don't lose the plunger or the little spring.

I found my notes and I evaluated using two different O-rings. Problem is that I never wrote down which one I finally chose in the end and for that, I'll have to take a carb apart. It'll take me a little more time. Give me a little bit...

Duh. Well of course if didn't do it when you were looking for it! You didn't realty expect it to do what you were hoping, did you?? It's going to wait for the most inopportune time to start acting up again! About the EC-5 test... Don't forget that just because you have a good signal at the test connector doesn't mean that you've got the same good signal in the coil of the solenoid valve. You could still have an intermittent at that connector or in the wire leading to the solenoid. In fact, the solenoid itself may be intermittent. But unfortunately you'll never figure that stuff out unless you can get it to act funny while you have some diagnostic equipment hanging on it. So what's the worst that can happen? Your BCDD can become activated when it's not supposed to (like when sitting still at idle) which can result in engine speed fluctuations and (at worst) maybe not returning to idle at all, but instead hanging up a little instead. Forget about it going lean. The BCDD has no effect on mixture, just engine speed. Speed only, not mixture. Think of it as a secondary device that pushes the gas pedal down a little when you lift your foot abruptly. Even though you lifted your foot, the BCDD holds the throttle open a little until the vehicle speed coasts down below 10mph. (Doesn't really pull on the throttle linkage, but does the same thing a different way). Is your car an auto or manual? If it's an auto, there is one additional complication in addition to the speedo amp.

I don't remember offhand what O-rings I used, but I'll check and let you know. Of course, since this was a custom job, I sized the grooves to the O-rings. You don't have to use the exact same ones as long as you adjust the groove dimensions accordingly. I probably have spares, so I you wanted to cover postage, I'd be happy to send some. Not sure if customs and shipping to Barbados would outweigh the cost of you just getting them locally though. I'll also see if I can check the throttle plate screw size as well.

Yes, on deceleration you would have high HC if the BCDD is not functioning properly. I know nothing about the emissions tests in CA (thankfully), but I'd be surprised if they catch that. It won't show up on any static test like idle, 15mph, or 25 mph. The only time it would show up is as a short transient when they took their foot OFF the pedal AFTER running one of the dyno tests. Not sure they'd flag that as a failure, but it's important to have it working regardless. And if that thing is clicking while sitting still at idle, your problems are not simply an adjustment issue at the BCDD. If you got clicking when sitting still, then you've got electrical issues somewhere.

Here's the thread where member sscanf was making his own BCDD diaphragms: http://www.classiczcars.com/topic/47935-air-flow-meter-fails-some-resistance-checks-repairable/page-2 Been a while since I looked at the details in the FSM, but I believe the BCDD is enabled when the solenoid is de-energized. That means that when you disconnect the wire to the BCDD it enables the system. The purpose of the solenoid and the amp on the back of the speedo is that the BCDD is disabled when the speed is very low (below 10mph). In any event, it shouldn't be clicking with the car stationary. Sounds like it's a bad connection somewhere between the BCDD and the speedo stuff... As for emissions... At idle, the BCDD shouldn't do anything to change any emissions even if it's malfunctioning. The BCDD just lets additional air around the throttle plate. There isn't any link between the BCDD and mixture ratios. Your idle speed will bounce around (like you said it is), but it shouldn't change the content out of the tailpipe. The only time the emissions are really impacted by the BCDD is when you're decelerating with your foot off the pedal. That's when the BCDD really does good things for emissions. But at idle? Shouldn't matter if it's working or not.

I'm sorry, but I never found any replacement parts for the BCDD. I know mine leaks a little as well, but it's an "internal" leak, not an external one. By that, I mean, my BCDD passes a little air through it even when it's not supposed to, but it passes from one side of the throttle plate to the other. It doesn't leak from outside the manifold to inside. So I've just got my idle speed screw set such that the total air around the plate (addition of what goes through the BCDD plus what goes around the idle speed screw) to my desired idle. I adjusted the idle speed screw and forgot about my leak. If you're is leaking to the outside world, then that's a more serious issue. And the thing about the clicking... That shouldn't be happening. I guess I'll get into the details in the other thread?

I used Viton (not Teflon):

You gotta remember that the filament resistance on a bulb like that is only going to be a couple Ohms, so if you put a 1K resistor in series with it, you'll drop 99.9% of the voltage across the resistor and the current will be throttled down way too low to glow the filament. If you want to cut the brightness I'd start looking at adding maybe an Ohm or two. It might not have been the black coating, It may very well have been the resistor. Academic at this point however. So speaking of academic, how did they drive it in the original application? Was there another module that supplied the intermittent DC to the ding-dong? I've mentioned before that Integras (my experience is with the earliest ones) used a ding-dong device for the headlight warning. I never looked at it... I wonder how they did it. I wonder if it's self contained with both driver and ding-dong.

That's awesome! I love the simplicity of the solution and I'm thrilled that the easiest solution actually worked! Of course, they usually don't, The bulb is glowing a little brighter than I think it should, so you might burn it out sooner than it would in normal application, but unless you purposely leave your headlights on, it probably won't matter. And even if it does go south, it cost what... fifty cents? If you find you're popping bulbs like gumdrops, then just use the flashy bulb to drive a transistor. Similar to what you drew for using the self-blinking LED to drive the transistor. You can use a resistor or two to adjust the current down a little and also to generate a base voltage for a transistor switch. Just remember, that the dimmer it glows, the shorter the off cycle, and the longer the on cycle will be. I love it when a plan comes together!

Timely question as I was just looking at some datasheets yesterday, but the end result is that I think you're going to have to buy one. I went looking for details because I was thinking about your idea of using the self blinking LED as a device to switch a transistor off-n-on and I was wondering if that would actually work. Problem is that I don't know how the self blinking LEDs work inside and I don't know what the current draw is through them when they are dark vs when they are lit. It would make sense that the current draw through the device would be higher when the LED is lit, but I'm not sure if that's really the case. They may simply shunt the current around the emitter die when they want it dark (think "short across the LED die portion") and the overall current might not change that much. So, I went looking for some info on datasheets and it's extremely vague. I didn't spend a whole lot of time searching out datasheets, but the two I found give absolutely no data on current draw ON vs OFF. Here's the two I turned up: http://www.kingbrightusa.com/images/catalog/SPEC/WP36BHD.pdf http://www.sunledusa.com/products/spec/XLUR50C.pdf So there is some info on the blink rate, but there's no spec for duty cycle or current draw in the different states. Two pages on solder temp profile and lead bending though! If you buy one and take some measurements, make sure you post your findings.

Awesome. I'll hook you up with a healthy home cooked meal and a lathe lesson! You ever been to the Jersey shore in winter before? It's very different than the shore during the warm months.

Haha! That's better than the piece of crap I would show up in! You gonna swing by and pick me up?

Awwww man, that sucks!! You can console yourself in the knowledge that it would have cracked eventually no matter what though!

We'll see... So would it be a travesty for me to show up sans Z and just be a "spectator"?

My current dash is in pretty good shape, but I know it's a ticking time bomb like they all are. So what does the other side of the leather cover look like? Is it all "baseball wrap" stitching everywhere, or is it pretty plain? I've seen some other leather covers that have stitched seams all over the place and I don't like the look. Looks like I'm staring at the back pockets of a pair of designer jeans from the 70'.

I've not taken one from a Miata apart, but I suspect all of the knob dimmers from every manufacturer uses some sort of a PWM concept by this time. It's way cheaper to build something like that than to do it the brute force and ignorance method they used in our Z's. Cheaper, smaller, lighter, more reliable, and more efficient since it doesn't burn up all that energy as heat. Nobody's going to use a big honkin' ceramic core pot anymore. And speaking of such... Since the original Z "pot design" is already ground based controlled (low side), it should be a breeze to convert the Z over to one of the newer PWM controllers instead of the original pot design for the dash lights if you're so inclined. You would need to run one additional wire (hot at all times" to a controller and you're done. There are lots of the newer styles that have twist knobs instead of roller wheels.

Thanks for the concrete input guys. This change is on my wish list for upgrades and I appreciate the input. I currently don't use my blower much at all. I suspect however, that if I had A/C (which I currently don't) I'd use it a lot more.

But.... (before I forget again). The self flashing xmas bulb would certainly be the easiest and simplest approach of all. So if you can get that to work, it'd be perfect. I'd explore that a little more before delving into other more elaborate means.

Man I would love to go to this. I'd remark about the long distance, but how can I complain in the face of a bunch of Canucks that are driving way farther than I would.