Captain Obvious

If that's the case then I think you've got other leaks elsewhere. You'd be hard pressed to suck that much air past a well fitting throttle shaft.

Here's your pic that I modified. I've added hash marks for the needle stations and from that you can see that the SM ends before it reaches station #14. However, even with the piston all the way up, you should be running somewhere between stations #12 and #13, so I don't think it matters. Interesting thought that the literature leads you to believe that it would have a true functional station #14: Anyway, it's all academic at this point, right?

I'm no authority on needles, but I just asked about the plating because I've not seen OEM (Nissan stock) needles that have been plated. Everything I've seen that I was positive came from Nissan was unplated brass. Now mind you... that's maybe twenty Nissan needles, so as I said, I'm no authority. Only plated needles I've seen were supplied in aftermarket rebuild kits. I've got a pair of plated N-54's and a pair of plated M-49's (from memory) from said kits on the bench right now. So, I'm drawing a distinction between OEM (Original Equipment Manufacturer, Hitachi in this case) and "OEM" ("form fit and function same as original, but not necessarily made by the same mfgr"). All that said, I did a little photo editing on your original pic and can tell you that the length of the N-27 needle you have there is the same as the ones I have, and the SM is a little shorter than the literature would lead you (me?) to expect, but not by much. It's missing the narrowest station (station #14), but even with the piston all the way up, you would still have needle in the nozzle, so it doesn't matter in application. I don't have the pic uploaded, but I will do that when I get a chance.

There are no seals on the throttle shaft. However... That's quite the leak to cause that dramatic of a drop in manifold vacuum. Is your throttle shaft all floppy and loose in the throttle body? I would be surprised if you didn't have something else going as well.

Thanks for the pics. Not as much of a length difference as I was expecting. Looks like less than one station. I'll double check the length on some of my needles and see if I can figure out where the original confusion lies. Do you think that silver needle is OEM Nissan, or do you think it's aftermarket?

And that's why I was looking for a ballpark number. My mixture screw was about fifteen turns out, and it seemed way too far. As for the AFM adjustments while running... I was doing my check at idle with the TPS idle switch closed so there shouldn't be any conflicting signals. My engine seemed to like more fuel at idle even with the idle enrichment switch closed. Might be related to a mixture screw that is fifteen turns out.

Forgot to mention... I ran my idle mixture screw all the way in as I counted turns, then I took it completely out, cleaned it up, and then put it back to where it was originally. Anyone have a good starting point for where the mixture screw should be? I know they will all be different, but a good ballpark starting position. I think mine is way too far out. I'm barely catching any of the sealing rubber and I'm assuming my PO messed with it. Might explain why my idle likes more fuel, but not less.

Nice! Would you do mine?

Today I inspected the gaps along the sides of my AFM vane and found that the gaps were slightly wider towards the tip than near the fulcrum. In other words, it appeared to me that the vane is in fact bent by accident, and not designed that way from the factory. So, with that in mind, I performed FastWoman's double anvil straightening method, and here are the results. Not perfect, but about as good as I could get it without taking off the waffle side and pulling the vane completely out: Here's my anvils. The metal one was my backup and went in through the downstream side for support. The wood block was my bending instrument and was inserted into the upstream side and hit with a hammer. The tube taped to the back side anvil helped direct the force nearer the tip of the vane because I couldn't get on it square due to the shape of the AFM body. Results? Didn't notice any change. Still runs fine. :laugh: So after I straightened the vane, I also played around with the vane position by moving the counterweight. The RPMs dropped when I tricked it lean and the RPM's went higher when I tricked it rich. In other words, it seemed to like more fuel, but not less. More tuning will be required.

I was messing with the throttle body on a Toyota Highlander and I don't believe the IACV uses a quadrature signals. IIRC, there were only two wires to it and I think it used a DC signal in conjunction with a permanent magnet. Analog like. :bulb: Wasn't "stand alone" as it was an application specific wart on the bottom of the throttle body, but it wasn't stepper. Looking at the design, it seemed to me that it would be difficult to control. Must be a fast loop... Another tidbit... My AAR was weird, and I finally figured out that it was intermittent. Finally failed hard and then was easy to diagnose.

I didn't get the chance to pull the AFM back off the car to take a better look at that bend in the vane, but I'll reserve judgment on the intentionalness (just made that one up) of the bend until then. In the meantime, I mentioned earlier that I believe my PO messed with the AFM settings. The glue glob on the lock screw for the clock spring gear has been pulled off the head of the lock bolt and some of the plastic gear teeth have marks on them (presumably from a screwdriver blade). So, question is... Is there any way for me to tell where the AFM was originally before anyone messed with it?

Bugs me too. It's just so open ended... I'd pay the shipping for you to send them to me for yet another set of eyeballs, but I can't believe there would be anything that I could possibly notice that wouldn't have been picked up by ZT. After all those pages of investigation, I just hate not knowing. :paranoid: Hey, now that you don't need those carbs to run the car, how about that shot of the SM's and the N27's next to the ruler?

Thanks Willoughby! You may have just saved me from "fixing" something that was never a problem in the first place! So the jury is still out on whether that bend is intentional or the result of a misfire. Glad I didn't jump the gun and start straightening it yet! Blue, Yes that gap appeared to be consistent to me as well when I was looking it over. I didn't measure it, but it eyeballed pretty even up the length of the side. That, and the consistency of the bend itself is why I was originally questioning whether the bend was intentional or not. So, I'll measure the side gaps, and if they're even along the whole side(s), I'll assume the bend is fluid dynamics black art. More news as that develops. Fastwoman, Yes, your dueling anvils make sense. I was just thinking that if nothing went sproing, it would be easier to adjust on the bench. Although, it seems I may not have to be doing anything with it. That would clearly be the best answer!

I'm sure your really really not supposed to do this, but... Can I take off the other side of the AFM to get better access to the vane? Might I even be able to take the vane completely out to work on it?

Mine runs fine at all throttle openings, but I believe I'm running a little rich. However, I'm still very new with the car and haven't even had the opportunity for a decent shakedown yet. I've been finding and fixing the problems as I discover them and haven't gotten to the point where I'm ready to really start "tuning". I believe my AFM has been tweaked by the PO, and that may be why I'm rich. In other words... If I put the AFM back to stock I may end up lean. Yup. I'm sure it's cast. At this point, I'm glad it's as flexible as it is. :surprised

Junk. I'll go $55 plus shipping. :pirate:

That's exactly why I wasn't sure if it was supposed to be that way or not. Fluid flow is weird stuff and since I'm sure these AFM's were highly characterized at the factory, I wouldn't be surprised if that feature was intentional. But unfortunately, it sounds like it's not. Crap. And that answers my next question of "OK, so it's bent. Does it really matter?" I was hoping that even if it was bent, it didn't have a great implication on how the car ran. Now I gotta do something about it... Only if you come over and help me tune the system afterwards.

Yeah, no kidding. The implications, as I'm finding out, are deep running. So not only am I finding blasting grit in places it shouldn't be, I've also realized that all of the original chromate plating has been blasted off the steel bits and has been replaced with paint. Looks great until the first time you wipe something with carb cleaner and take the paint off exposing the untreated steel beneath. I would much rather deal with a little dirt, grease, oxidized aluminum, and old chromate. Even if it's starting to fail in spots.

Nice. I want to convert my 77 up the 78 design for the crankcase venting and AAR because I think it's a better system and should do a better job of keeping the AAR cleaner inside. One of the things that I don't have is the rubber hosing, and I agree with you that your design looks better than stock. I think I may plagiarize. Errr... I mean "flatter".

So I'm giving my AFM the once over before putting it back on and I notice that the air metering vane looks odd... Here's the outlet side with the vane closed: As you open the vane you can see that the bottom edge of the vane is not straight: So I'm guessing that it's not supposed to be that way, and it's bent as the result of a backfire into the intake or something? And simply for posterity, here's a pic from the intake side:

Thanks for the parts digging guys. I'll probably go the used route before resorting to buying new. Don't get me wrong about my PO. It's not like he blasted the inside of the throttle body. It's clear that he at least tried to keep the grit out of places it shouldn't go. Problem is that even if you're careful, grit sometimes gets where it shouldn't. So, it's not like I'm expecting to dump a spoonful of grit out from inside my BCDD, but it only takes one bead on the sealing surface of the valve inside to screw it up. Do I think there's a spoonful in there? No. Do I think there's a piece or two in there? Absolutely.

I like it. I'll probably do that once I work out the simple bugs. Nice broken exhaust manifold bolt.

Haha! Weird isn't the word I would use... :stupid: So far things are going pretty well. This whole thing started with me removing that extra throttle return spring you noticed. Once I took off that extra spring, I discovered that the throttle would not always return to min. So it seems the previous owner put on that extra spring to fix the return problem, but in fact it was a band-aid and didn't address the root problem. He added more force but didn't fix the real problem in that it should not NEED more force. After cleaning out all the grit, my throttle body movement is smooth and with the stock return springs, I get a good positive "clink" onto the idle stop each and every time. The linkage from the throttle body to the firewall is smooth and free turning as well. Now that it doesn't take excessive force to close the throttle plate, I will take your advice on adjusting out all the slop in the pulling direction. My return springs now be able to do what they are supposed to.

The whole host of issues? I just put some details in my throttle linkage thread http://www.classiczcars.com/forums/showthread.php?45815-Throttle-Linkage-Improvements&p=395674&posted=1#post395674 But the summary is that I've discovered that my previous owner got overzealous with the bead blaster and sprayed things he should not have. Here's the host I've found so far: Blasting grit in the throttle body and TPS making the throttle shaft movement grainy. Blasting grit making all of the throttle linkage ball and socket joints sticky. Blasting grit in the sleeve bearings where the throttle linkage mounts onto the intake manifold. Blasting grit inside the plastic spherical bearing where the throttle linkage mounts to the firewall. Not related to my throttle issues, but I found blasting grit inside my distributor as well. So what made me start looking at the BCDD? To be honest, I don't have any performance reason to believe there's anything wrong with it, but with all the grit I've found elsewhere, it is impossible for me to believe that it didn't get inside the BCDD as well. But I don't want to open it up without replacement parts first. If you open one, I'd love to see pics. I think I've got a pretty good idea of what's inside, but without opening one up, it's simply speculation. I just hope he spared the AFM.....:sick:

Thanks for the tips guys. This whole thing started with a hunt for an issue where my throttle would sometimes hang up just a little bit and I would have to blip it to get it to return to the low end idle stop. I started at the front end with the throttle body and have been working my way towards the pedal and have found and fixed lots of problems. I have also figured out what's going on... All of the issues I've found stem from the root issue that my previous owner got overzealous with the bead blaster and hit everything. The car sure was clean when I bought it, and now I've begun to understand why! :mad: So I had glass beads in my throttle body and TPS making the throttle shaft movement grainy. I had glass beads making all of the ball and socket joints sticky. I had glass beads in the sleeve bearings where the throttle linkage mounts onto the intake manifold. I had glass beads grinding away inside that plastic spherical bearing. Anyway, everything else has cleaned up pretty well and doesn't seem to be badly worn with the exception of that spherical bearing at the firewall. I guess I'll clean that part up as well and put it back on and see what happens. On a related note, I figured out why I wasn't getting full advance on my distributor. Yup... glass beads mucking up both centrip and vacuum advance mechanisms.