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Thinking about this all day(and night I'm a shift worker), with the car wanting to run with the CHTS unplugged (this will cause the ECU to go full rich) it would seem by what you describe is that you have un-metered air getting into your engine. So keep looking for the vacuum leak. This could be the intake manifold gasket in addition to all the other stuff I mentioned.
The FSM tells you how to check the Aux Air Valve by pinching the hose either to or from the valve. You could do this with any/all the 7/8 and smaller hoses with a needle nose pliers to see if it changes how the engine is running, assuming you can get it to stay running.
 

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Discussion Starter · #22 ·
Ok so two questions that have come up while going over my car and the info you guys provided.

The first is a general engine question that I am more curious about than it probably matters. While going over stickers and stuff under the hood I noticed that the Emissions sticker says my engine is from the "L24/28 F family". I thought the S130s had the L28E, or is this all the same thing and I just don't know how to interpret things?

The second is more technical and relates to Emissions components(at least I think it is the Emissions stuff). In going over the vacuum diagrams from the FSM I feel like I am either not reading the diagrams correctly, or the BCDD/Throttle Body installed might not be from my model specifically? As far as I know, I have a '80 280zx, MT, Non-CA US Emissions, Non-Turbo. The diagram looks like there are 8 vacuum line connections on the Throttle Body/BCDD. I have counted several times but I only seem to have 7 bungs or tubes total on the Throttle Body/BCDD that is installed in my car. Am I reading things wrong, is there a manual or instructions for these parts that might tell me what each tube is for specifically?

Here is the diagram I am looking at for reference.
Rectangle Font Parallel Schematic Engineering
 

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L24/L26/L28 are all very much alike and would be considered of the same family. 1975 saw the change over to EFI.
Most of the vac hoses are emission related. To clean things up you can bypass the Thermo-vacuum valve and run ported vac right to the distributor. Plug the one that goes to the EGR, its not doing you any favors. The one that goes to the carbon canister opens and closes the purge valve on the canister you can take it or leave it. or Chances are the BCCD is non-functional. There are enough discussions on here for you to make your own decision on what to do with it. My 81 has it removed but my 83 still has it. The BCDD internals could be giving you the problems you are seeing if it is stuck open. Try pinching off the big hose that goes to it to see if your car runs better. The removal of the BCDD can cause backfiring or some say. Some people call it the anti-backfire valve. I don't have a backfire issue with my 81 even with the BCDD removed.
I count 5, unless you are counting the manifold vacuum supply to the Thermo-vac valve (6) and the one to the BCDD (7)
The decisions you make will be dependent on if your car has to go thru emission testing where you live.
 

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Have you been able to get the car to run any better? Really the only emission related item that could be giving you the problems you describe is the BCDD if it is stuck open. It has happened to others. You can disconnect every hose from the throttle body, run a new one from ported vacuum to the distributor, plug all the rest and you will not have any running issues. Most of what you see is the restriction of vacuum being applied to the distributor/Carbon canister and EGR valve until the engine has warmed up to operating temp. The BCDD puts air into the intake to keep the pressure in the intake "normal" 18" mercury.
 

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Discussion Starter · #25 ·
L24/L26/L28 are all very much alike and would be considered of the same family. 1975 saw the change over to EFI.
Ok cool, I think the part that threw me off was the 'F' family thing. Good to know it's all the same.
I count 5, unless you are counting the manifold vacuum supply to the Thermo-vac valve (6) and the one to the BCDD (7)
The decisions you make will be dependent on if your car has to go thru emission testing where you live.
Unfortunately Colorado does do emissions, but for this car it is just a two speed idle test because of age. So I will have to look into that to see about removing things, the car was originally sold from a dealer here in CO so I kinda have to assume I need the emissions pieces. Ok so the way I was reading that diagram, there are 3 hose connections on the distributor side(or top of the picture at least) and then the 5 on the opposite side of the distributor(bottom of the picture), which ones am I counting that shouldn't be? Also it kinda looks like the third line coming off of the D2 valve(left to right) t's into the first line?

I apologize, this is all probably really basic stuff for most.
 

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Discussion Starter · #26 ·
Have you been able to get the car to run any better? Really the only emission related item that could be giving you the problems you describe is the BCDD if it is stuck open. It has happened to others. You can disconnect every hose from the throttle body, run a new one from ported vacuum to the distributor, plug all the rest and you will not have any running issues. Most of what you see is the restriction of vacuum being applied to the distributor/Carbon canister and EGR valve until the engine has warmed up to operating temp. The BCDD puts air into the intake to keep the pressure in the intake "normal" 18" mercury.
I honestly don't know. I was replacing vacuum lines and it sounded/felt like things were smoothing out, but every time I try to run it with the CHTS plugged in it just can't start or can only barely run for a few seconds which hasn't changed. I've checked timing a couple times, and other than the fact it is timed to 0 rather than the recommended 10 it seems to be fine. I don't know how much that matters or not. I did try to run it with the sensor unplugged for a few minutes, revved the engine to 2k RPM for a minute or two a couple times to warm up the engine. Then once it was warmed up plug in the sensor. When I do this there is no change for a second or two, which is a bit longer than if I do the same thing cold, then it always sputters out. So this led me to check my vacuum lines and found that it didn't look like had things plugged in properly, so I disconnected all of the lines from the D2 valve that didn't seem to match to rerun them just to be sure. Which is now where I am having issues understanding the diagram.
 

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WOW. I just spent the last hour reading thru the emission section of the FSM for your car. Talk about FUBAR! It seems you have a 2 stage thermo-vac valve (D2) that applies 1/2 or full vac to the distributor during Cold/Warm up/normal operation of your car and vacuum to the D1 thermo-vac valve that opens the EGR valve once both Thermo-vac valves are actuated. The chances that both of your Thermo-vac valves function correctly and that the check valves and delay valves all function as designed is probably zero. Everything has to function properly in order for the system to work as designed.
Your emission test will probably be done when the engine is already hot so most of the system is mute. You should find out what emission testing you will have to go thru. Pilgrim can you add to this? He is in Colorado. There is not a OBD port on the car, not even OBD I. I would guess they do CO testing at idle.
It this were my car, instead of spending the entire winter trying to find Thermo-vac valves and delay valves, I would re-arrange the vacuum lines so that I had ported vac to the distributor 100% of the time and plug all the rest. The perfect size plug is a BB for BB guns. Put one in the hose at the EGR and one in the hose to the BCDD. That way it looks stock but is set up to run normal. Leave the line to the charcoal canister alone.
I looked at the BCDD diagram and I was mistaken, there is no supply hose, it is all internal. It seems yo have not found your un-regulated air leak yet, so look at the testing of the BCDD valve.
 

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Have your mechanic friend, or you put a Hand Held vacuum pump on the Fuel Pressure Regulator. If it does not hold vacuum then it is bad. Another part to check with the Hand Held vacuum pump is the Vacuum Advance and it too should hold vacuum and if not it's bad and needs to be replaced. Due to the age of these cars, the diaphragms inside both of these parts crack and leak.
 

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You're in deeper than I ever have been. My car is a turbo, which means extra vacuum hoses and controls but also slightly different electronics. Not sure I can be of any particular help.
 

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Discussion Starter · #31 ·
Where in Colorado are you?
I live in Thornton, CO.

I am pretty confident I messed up the lines when I was replacing, mostly because the line marked as the "Manifold Vacuum" was split to also run to the distributor, and there wasn't any line from distributor to anything else. I want to try and fix that, as I'm sure air going the wrong way probably doesn't help. When replacing them I tried to do it one line at a time so that I wouldn't get things confused, so either I got it confused anyway or it wasn't right to start with. If that doesn't work, I practice with my BB gun regularly enough I'm sure to have some unwanted bb's I will plug things up with. While I'm at it I'll get a hand vacuum pump and check that stuff as well. I probably won't get around to that until this weekend though, but I will update once its done.
 

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Pilgrim I was referring to what do they all check/do when doing emission testing in Colorado
I re-read more carefully...and I see the question was related to emissions testing. Yes, they do that at idle using a tailpipe sniffer. I've had to test my car a couple of times. Common wisdom is to get the car well warmed up to full operating temp before doing the test....like a 15 or 20 minute drive first.

When it comes to re-plumbing or moving any of the emissions lines, I have no referent and no advice.
 

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Discussion Starter · #34 ·
I took my time today and went through and redid all of the vacuum lines. It didn't completely soIve the problem, but I got it running with the sensor plugged in. Was able to start/stop it several times and it will fire and run. Still weak, and runs way better with it unplugged, but it is still progress.
 

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Discussion Starter · #35 ·
It has been a few weeks and I thought I would post an update. So Kickstand80 was awesome and stopped by to take a look at the car. He found a couple issues I was not fully aware of, and provided an amazing amount of information and tips. I am very grateful for his time and effort, it has helped me out tremendously!

So, the end result was that I need new connector ends for the injectors/sensors as mine are well worn, a couple just aren't providing power to the appropriate sensors, and a couple injectors needed replacement. I replaced the faulty injectors and have ordered a set of plug ends. Now bruce83na had mentioned earlier in this thread to check the fuel pressure regulator, I don't yet have a hand vacuum pump and it didn't cross my mind when Kickstand80 was helping me. So I asked my mechanic friend if he had one, he didn't, but he said there was another way to test it. What we did was start the car then pull the vacuum line off the pressure regulator and plugged it since the engine would die if it was open. After doing this, the engine was able to run with the CHTS plugged in. I am now looking for a suitable replacement for the pressure regulator as well.
 

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By doing what you did, if the fuel pressure regulater diaphram was bad and leaking vacuum, there would be gas flowing out of the fitting. You do have to check that vacuum advace, as due to age I have seen a lot of them that leak.
 

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Thanks Bruce83na, we did check the vac advance while I was there with my vac pump and it is bad. Benroberson86 has the dual port vac advance on his car and had zero chance of ever finding one. He is looking at other options for that repair.
 

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Fifteen years ago when I found the vacuum advance on my 280ZX was bad, armed with my hand-held vacuum pump, I headed to a local junkyard that had at least 3 cars. The vacuum advance on the first 2 cars leaked, but the 3rd one held fine, then with the intention of only taking the vacuum advance I removed the distributor cap and found everything underneath to be almost new, so I took the whole distributor.
 

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Have you EVER seen a dual port vacuum advance unit on a 280zx? This was a first for me. I dont know if this a push/pull advance or what it is. It does show it on the vacuum routing diagram but does not explain the purpose. I have pulled everything from my local yard and have a good spare single port for my cars, but everything had dried up in the NOS market for new parts. I know there is someone in Australia that rebuilds them.
You have a spare dual port advance for a very late 79 really early 80 you want to donate to a good cause?
 

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Discussion Starter · #40 ·
I wanted to post an update real fast before the holidays as I am sure to not post for a while during.

The injector wires have been taken care of, I do need to verify that the two connectors not getting power before get power now, but honestly if they still aren't then it pretty much has to be a fuse so I am not in a rush to check that just yet.

I did some research on the vacuum advance and found that the dual can/port version that I have on my car is just another emissions related piece. From what I was able to dig up, the port or can closest to the distributor is a vacuum retard used to make the engine burn hotter at an idle for emissions reasons. The second is the typical vacuum advance used to keep up with engine rev. So I was able to find a dual can style vacuum advance, it wasn't listed as being specifically compatible with the 280zx engine though, so I'm curious what parameters I should be checking to see if it is compatible?

The fuel pressure regulator was believed to be bad based on the idea that with the vacuum hose connected, the vacuum being applied was enough to close the pressure regulator completely at an idle. This would cause there to be more fuel pressure than required at idle causing there to be too much fuel in the intake at an idle. The thought being that there would need to be something inside the pressure regulator that applies counter force to the vacuum to keep the pressure regulator open at idle. This could be a very misinformed idea since I don't know all the inner workings of a pressure regulator. In any case finding a direct replacement doesn't seem to be all that difficult, just a bit pricy so if I am wrong please let me know I can use the extra cash :D.
 
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