Sometime in the last 43 years anything could happen. But it's good, the anti-diesel valves prevent engine run-un which was a big problem with the 72s. Mine kept running when the key was turned off, and it took careful tuning to minimize it.

Got a photo of your lil Datsun?

I do have a 72. I wonder why I have a anti diesel valve?

Glad to hear you found the cause.

The Anti-diesel valve was only used on the 1973 1200 in USA. For some reason I thought you had a 1972. Yes, it must be working for the engine to idle.

Turns out it was a faulty wire in the anti diesel solenoid! Thanks for the help!

oh I forgot, this is all covered in the glovebox Owner's Manual. I hope the photos are more helpful than the diagram.

1972 page 30




One tricky thing is just getting the air cleaner removed. Details and photos are at Air Cleaner Removal

Sure thing. The throttle opener is not so much where the hoses go, but knowing that there are hoses and checking each one. If these hoses are not hooked up, don't try to reconnect them -- If the Throttle Opener is not operative, it won't cause an idle problem.


Intake Manifold hose is connected to Throttle Opener Solenoid



Throttle Opener Solenoid hose is connected to Throttle Opener

For 3, could you show me where the hose for thr throttle opener diaphram is connected to?

I had the exact same problem here too. Rough idle but would be fine when putting foot down.

Also check these couple of things:

Intake manifold bolts are tightend up and no air leaks around gasket
Check fuel filter make sure it doesnt need changing (mine did!)


The thing that actually was wrong with my carb was my Dad (mechanic) said it was possibky crap in the fuel line/jets somewhere.



Try this cause it sounds exactly the same as what happened not more than a week ago for me.

Take of air cleaner.

Start car up,

Go over to your carb and locate the throttle control

Rev your engine up really high til its up around 4,000 revs or so (not drastic but need to rev it a fair bit)

Why your still revving it then put your hand over the intake of the carb (or use a piece of flat cardboard that wont get sucked through, cause i was too chicken to do it with my hand)

Block it off completely, your engine will start to die, let it drop down revs as far as you can without stalling (doesnt matter if it does stall) then see if it idles. Repeat this process 3 times and if there is any crap in the system it should pull it through. I did it 2 times and it completely fixed the idle.

Shortly after i checked the fuel filter and surely enough it had lots of crap in it.

Sounds very similar to my problem so do give it a shot.


Hope it helps! Just thought i'd mention it cause it helped me! Thanks Dad!!!!

If not then probably definately something dd said!

Matt

These are the hoses to inspect:

1. Between Carburetor and Distributor (vacuum advance hose). One end can only be inspected with air cleaner removed from the carburetor






2. Between manifold and transmission (vacuum modulator line)
Connected to intake manifold by short length of hose:



Connected to transmission by a short length of hose:



This can by viewed by lying under the car on the driver's side.

* If it is not connected, shifts will always take place as if the throttle is floored (hard shifts).

* If the diaphragm is leaking (won't hold vacuum) it will leak transmission fluid into the engine, creating smoke.


3. Hoses for carburetor
* Hose for pull-off
* Hose for vacuum opener (if your 1200 has it)





Vacuum Opener is the most complicated system on the 1200. The good news is all that needs to be done is make sure the hoses are good.






4. Hoses for air cleaner
* Hose from bottom of air cleaner sensor to intake manifold
* Hose from bottom of cleaner to the flap motor







5. Thick hose for PCV system. The rubber hose might be soft and squishy, and if it won't stay connected, needs to be replaced.

The next thing to check is a visual of the fuel float level.

1. Start the engine, run it for 30 seconds, and then turn it off.
2. Under the hood, peek under the air cleaner. The air cleaner doesn't need to be removed.




You may need to wipe grime off the glass to see the level




If the level is near the dot in the center of the glass, that's good. If the level is low, then it needs to be adjusted to solve the idling issue.