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Discussion Starter #22
Well I'm glad that it got figured out! Now to hunt a good one down.... Due to the economic hocus pocus going on right now I'm cutting back spending but eventually I'll go out and grab one.
 

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Discussion Starter #24
While I get that that's an optio, I'm a real stickler for leaving everything as it was built. That includes emissions stuff too. Just preference. :)
 

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Discussion Starter #26
OK PROBLEM HAS BEEN SOLVED!!!! I'm going to be doing a pretty extensive write-up here so that hopefully another visitor trying to fix their 280ZX wont fiddle around for months trying to locate the issue like I did. So here we go...

Problem Symptoms
  • Excessive Bucking/Rocking when letting the foot off the gas (especially at certain RPMs). Goes away when accelerating.
  • RPMs go down quickly when shifting, as in TOO quickly.
  • Not sure if this was related fully but slight hesitation when accelerating.
  • The SlayZombi classic "whomping" sound so elegantly described in previous posts.
Solution
I figured out this specific part was an issue when I finally had enough and just took it to a mechanic to try and solve it. They came out and just started pulling vacuum lines to test, and notice the "whomping" noise went away when undoing the vacuum line from the BCDD (Boost Controlled Deceleration Device) to the top of the intake manifold. I tried pinning down a replacement part to no avail. Seriously, good luck finding one. You never will! So then I took a look at this post: Info on BCDD - Boost Controlled Deceleration Device

And began my quest to just fix whatever was wrong with mine. So I went ahead and took mine off and got down to work. This picture below is what it looks like on a 1982 280ZX, and the instructions will be tailored to that. Earlier models have different pieces to this system so just work with me here. :)

106783


So after you take it off the car, you need to first take off that top clip holding the nut onto the brass casing (if you still have one). Then, take off the nut and count the threads beforehand so you get the correct adjustment when putting it back on. Take off all 6 screws and REMEMBER HOW THEY GO! They have an alternating pattern of long-short-long-short. After that, the brass casing should come off and expose a spring like this:
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Now, you can't take this off until you separate the first "section" fro the middle section, as in separating the two pieces sandwiching the "very important" membrane closest to the brass casing. I can not stress how careful you must be in doing this. Based on how unique the membrane appears to be, if you rip it, it's all over and you might as well get a new BCDD. The way I separated it is by tapping an exposed lip on one of the sections LIGHTLY with a flathead and a wrench. Unfortunately, I didn't bother taking pictures form this point on so I will explain it as best as I can... After the two pieces come apart, you should see a screw on the underside of the spring-side section. Undo this so that you can take the spring off of the section for cleaning. You can also carefully remove the "very important" membrane off, which is attached (keep it that way!) to the cylinder with the valve on top. Now the next section you need to take apart is the "kind of important" membrane/gasket closer to where the BCCD connects to the intake manifold. This one appears to be regular gasket material with no noticeable "unique" features so don't sweat it if it rips a bit. Mine was so cooked that I actually had to have a bit of RTV sealant on the gasket ends to prevent air leaks. After that is off, you have the entire system apart! Clean all metal pieces with carb/choke cleaner to get any grime and oil off. There is not supposed to be any oil in the system but blowby can cause this. I believe my issues were caused by excessive oil and dirt(??? HOW??) buildup inside the system all along the seals and even the pathways for vacuum to travel. Avoid spraying anything on the membrane. I don't know if chemicals from cleaning damage it but let's not try to find out. After a thorough cleaning, put it back in reverse order, making sure everything is aligned (watch the small air holes!) before setting the 6 screws back in. Peel off the most likely cooked BCCD-manifold gasket and put a new one on, securing the two screws back in. I don't know where to find the individual gasket for the BCCD, but mine came in a kit with ALL gaskets located here:


Outcome
Well if you got through that wall of text, congrats! Hopefully this solves all of your issues. After fixing this, I had no more weird sounds, my RPMs dropped at a reasonable rate in between shifts, and most importantly, the car stopped bucking during coasting/deceleration. Hope this at least helps SOMEONE save time and money. Thank you all for your support and at least trying things out with me and offering solutions. I can now say that as of now there are NO known issues with the car finally! :)
 
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