Here goes. Just bought this 87 truck...22r, pulled the plugs, noticed they were white-meaning timing is off or getting overheated somehow. So I checked the timing and leaving the 2 hoses connected, found it to be 12 degrees btdc. So I pulled the two vacuum hoses off the dist....no change-still 12 btdc. So...ever so gently...I attached one end of the hose to the dist and sucked on the other end and found the inner advance not working..outer works fine. I then reset the timing to about 2 degrees btdc with both hoses plugged... reconnected the outer vacuum hose and then put a golf tee in the end of the inner hose, leaving it disconnected from the dist. The engine has always idled great and still does. I am hoping with correcting the timing to specs and plugging the inner vacuum hose I have stopped an air leak which was causing the engine to run lean and hope my gas mileage improves, better than the 20 mpg it was getting. My question is do I need to replace the diaphragm can on the dist or should I not bother? What is the purpose of the inner vacuum if it idles fine without it? Thanks to all who respond...

 

I'm no expert on this, but I have a 1985 2wd 22r that I have put a Weber 32/36 and Offenhauser intake on, along with removing the emissions. Thus the inner (closer to the engine) diaphram is now blocked off with a cap, per instructions from LC Engineering. The inner one is controlled via the emissions system, the outer is just vacuum advance from the carb. Plug off the inner and forget it.

 

For the thing you said about your engine was running lean before and fixing this you hope for better mileage. With making the motor run more rich you will burn more not less fuel. These motors are supposed to run at 8* BTDC. I'm pretty sure I am right on that one. I ran my 22R at about 10 or so and it runs fine.

 

White-ish looking plugs indicate a lean mixture. Replace the vacuum advance diaphragm; the truck will lack power and gas mileage without it functioning. Your idle will become even smoother too.

I have found that purchasing an OEM diaphragm from 1sttoyotaparts.com was much cheaper than buying an aftermarket one.

 

The main diaphram is farthest from the distributor and controls the main vacuum advance. The sub-diaphram is only pulled at idle or while decelerating, mainly for smog reasons. I had the main one go out in my truck and I got lots of pinging under load and lots of sputtering while decelerating or coasting down a hill. The sub requires less vacuum to pull, so having a main diaphram blown throws your curve way off. It is best to replace it.

Different 22Rs require different degrees of base timing. My truck, which is California smog, requires 0* at idle with both hoses disconnected. When I re-connect the hoses, it goes to about 10-12* BTDC. Go by the sticker on your hood when setting the timing. When replacing the vacuum advance, make sure you get the proper one for your truck. They are different for Federal and California smog trucks. They are interchangable, but the advance curves are different. While you have the cap off of the distributor, check that the mechanical advance works smoothly and that the vacuum advance plate also operates smoothly. I had to clean out mine and re-grease it when I changed my advance. It made a noticable difference in acceleration and fuel economy.

 

Thanks to all who replied...I have no sticker under the hood, read some threads and figured 0 or 5 degrees btdc were my choices..so I put it at 2. I am not sure of the history of the car..how does one know if it is CA or Federal? It is running great with the sub-diaphram hose plugged..my plugs are turning tan colored so I have stopped the lean air leak. Better gas mileage too. Can the diaphram be replaced in the dist vacuum can or do I just by the vacuum advance can on the side of the dist?

 

Federal smog trucks, in your year, should have a smog pump. California smog trucks have a more computerized air suction system and no smog pump. They have a round black device on the passenger side fender with two vacuum hoses going to the carburetor. If you are unsure about the timing, start at 5* and retard it if it pings. There is a company that rebuilds vacuum advances, but I would recommend buying a new one. I had one rebuilt for my Subaru and it broke again not long after I had it rebuilt. They would have to be cut open and I would guess that it would be difficult to get an air tight seal again.

 

I just checked the repair manual and I believe that I am wrong about the smog pump. I think those were on older trucks. From what I can tell, California smog trucks have an oxygen sensor and Federal smog trucks do not.

 

If the sub diaphragm is not being pulled out would it cause it to idle poorly? What is the vacuum hose expose to be attached to? Mine is hooked up to a sensor on the passenger side fender.

 

If the sub diaphram is not being pulled then it will idle a little rough because the timing will be retarded more than it should be at idle. The line goes to one of the ports on the carburetor. If I remember correctly, along the steel vacuum line is another port going to a switch on the fender that is for the fuel cut system. In some models, there is also a T in the vacuum hose near the distributor that goes to a high altitude compensation device. Basically, the line should go to the sub diaphram and a vacuum switch, and possibly an optional HAC valve. There should be a vacuum diagram on the underside of your hood that might help clear up what I am describing.

 

one is a retard, one is an advance:
... under low intake vacuum (i.e. accelerating), the timing gets retarded
... under high intake vacuum (i.e. cruising at constant throttle), the timing gets advanced
... under light acceleration, the two are 'pitted against each other' to determine the appropriate amount of timing
-hence two vacuum lines. when both lines are at the same vacuum, there is no change to the timing, which is why you have to disconnect and plug both lines to set the timing.

I don't know where you're at, but if you want, I have a complete distributor out of a previously-running 88 Cali model that, if you're willing to pay for shipping, I'll send to you, and if it works, give me what you think is fair. If it doesn't work, pass it to the next guy and send me half what you get for it.

...and for the record... 20 mpg is pretty good for a carb'd yota.

 

The 22R has two advance diaphrams, which is different than the usual vacuum advance, and I believe it is done that way for smog reasons. The advance/retard design you are refering to was used on earlier engines (8R I think).

 

Tell that to the 22r the distributor came off of- one diaphragm moves the pick-up plate one direction (advance), the other diaphragm moves it in the other direction (retard)... push-pull, if you will.

 

Stop and think-
one diaphragm with ports to each side of the membrane...
suction on one side pulls it one way...
suction on the other side pulls it the other way...

 

That is originally how I thought it worked, because that is what makes sense. I had a pinging problem in my truck a while back that I could not figure out. I did a lot of research and testing and found out that there are actually two vacuum advance diaphrams in there. One is pulled off of the fuel cut port, which is at idle and when the throttle is closed. The other one is pulled at all other throttle positions. You can check on your spare distributor. Applying vaccum to either port will pull the plate in the same direction.

 

I'm not going to argue. No point in it. Though I've seen vacuum on one port push the plate one way and vacuum on the other port pull the plate the other.... You win.

 

Would you happen to have a picture or possibly a part number of the vacuum advance that you are looking at? I am not trying to argue about it. My 1987 FSM & my own personal tests shows what I have described above, and if you have something different then I would like to know so I will be familiar with it if I happen to run across one on a future Yota project.