vacuum advance

[2wagons]

Hello again, my 87 just won’t get over 27 mpg so I checked the timing and vacuum advance. I have the vacuum advance with 3 ports: one lower (main advance) and two upper (connected to the altitude adjuster). When the RPMs go up, my vacuum gauge shows a vacuum is induced on the lower hose and the timing advances indicating that the lower diaphragm is working and the lower diaphragm will hold a vacuum. Neither of the two upper ports will hold vacuum indicating the upper diaphram is leaking.

The timing is checked with one of the upper port hoses disconnected and plugged. The timing is dead on. The FSM says to re-connect the upper port and watch if the timing advances to 13. This doesn’t happen as the upper diaphragm can’t hold vacuum. So does anyone else have this problem? Do you think the secondary diaphragm not working to increase timing will decrease MPG? I would like to replace the vacuum mechanism-does anyone here as an old one the want to sell? The performance of the car doesn’t seem to be degraded too much by the leaky secondary diaphragm.

[ARCHINSTL]

2wagons -
YES - I have the identical problem (among others...). I have just finished trying every check in the wonderful FSM, and have concluded that at least the upper diaphragm is bad. The HAC is superfluous in my location (St. Louis), and I have tried disabling it, which had no effect, whether pro or con.
The advance will only work with increasing engine speed, which leads me to conclude that the centrifugal part is the only one that works, as there is a vacuum "available" on the upper tubes and the lower tube. Oddly, when I apply a vacuum to the lower tube, the advance inside the distributor will move and function, but not when the vacuum is supplied by the engine for ? reason.
So - I bit the bullet and ordered an OEM from Butler Toyota in IN, for $120<span style='color:red'>*</span>. I also ordered an EGR vacuum modulator ($63), as that is also shot, determined after numerous tests more involved than in the wonderful FSM. Butler had the items in stock and acceptable prices - thanks to a takza post for the info. I thought I'd go with the OEM instead of an Advance aftermarket for $106 plus freight. <span style='color:red'>*</span>Free Freight over $100.
Incidentally, to anyone contemplating an FSM purchase - I used a bunch of gift certificates to Borders and had it order the book direct from Toyota; it did not save any money, but was convenient. HOWEVER, the very thick book has fallen apart in the last couple of months. The quality of the "binding" is crummy, at least compared to my '88 Mitsu truck book. I am writing Toyota about this $90 piece of opcra, but do not expect a bone. I will also comment on the lack of "If this is bad, then the result is...".
I will advise on the results when installed.
Tom M.
P.S. I note you have an '87: There seem to be a dearth of posts in our forums about the variable venturi carburetor used on the later 3E engines, compared to what one encounters when Googling "hesitation" and "stumbling". My impression has been that this carburetor is one of the worst ever used - even the Car Talk guys diss' it unmercifully. Is this reputation deserved?

[2wagons]

Archinstl,
have you installed the new vac advance yet? if so has it helped? I looking forwad to see how the new vac advance works. BTW, does the lower diaphragm hold a vacuum? if so, then the lower diaphragm should be good. I found that the carb induces the vacuum to the lower diaphragm under higher RPMs, just hook up a vac guage with a "T" in the correct vac line to see if the carb is pulling against the diaphram. If not, the probelm is between the carb and diaphram. I tested the upper diaphragm by pulling a vacuum on it and it failed from both ports.

The 3E was/is an engine with a horrible side mount carb prone to lots of problems, numerous tech bulletins have been issued for the 3E carb/engine. My engine is a 3AC as is yours, I assume.

[ARCHINSTL]

2wagons -
The new modulator and vacuum advance will not be here until Thursday or Friday, and it may be Saturday or Sunday before I get them installed - kidsitting for a daughter. > >See Edit below < <
As mentioned, it is odd that when I apply a vacuum to the diaphragm, the distributor advances, but not when the vacuum is supplied by the engine (a vacuum is present from the engine).
I plan on eventually dismantling the advance (and the EGR modulator) to see if they can be fixed. I will pass on all info, but will do the installation results first.
I did think that the 3E engine went in all Tercels from 1987 through 1990 or so; did the Wagon keep the 3AC and feedback carb, whence the dearth of posts in our forums?
Tom M.
EDIT: Butler in IN advised that it had to order the parts from its warehouse and they would not be shipped until Friday or Monday - were supposed to call me if a problem, but did not. Oh well, its price was good (for a dealer), and the freight is free...

[2wagons]

Archinstl,
The vac hose to the primary diaphragm also connects with the EGR.The EGR could be leaking enough air to stop the vacuuum from pulling on the distributer. Did you try jumping the vac hose around the EGR to confirm you are getting suffucient vacuum from the carb? If not, the carb may be at fault.

[ARCHINSTL]

2wagons -
Yep, I checked the vac immediately from the carb and it is supplying a vac to the primary diaphragm. In fact, the actual measurements are: At idle, 10+ inches, and at 3K RPM, 20+ inches, each of which should move the advance. Again, the odd thing is that with the carb vac, that diaphragm will not move/move enough to advance, while it will advance when I apply a vac with the pump.
I cleaned the port in the carb with cleaner and high pressure air. It acts this way with or without the air cleaner, and regardless of the RPM. I took measurements at both speeds in front of and after each tube in the distributor and EGR system - tedious.
I also checked the vac (or lack thereof) before and after the EGR and the check valve, at idle and at 3K RPM, and all is as it should be (I had hoped I could find a deviation, but it was OK). I also blew into the tube from the EGR valve to the modulator (yukh), and it did not cause the modulator's diaphragm to rise as it should.
So - not only does the distributor not advance to the 13 degrees, but the EGR valve shows barely a pound or less when it should show "a little" - (5"-10" ?) at 3K RPM, per the wonderful FSM.
Tom M.

[Gasoline Fumes]

did the Wagon keep the 3AC and feedback carb, whence the dearth of posts in our forums?

Yeah, the other Tercels changed completely in 1987, the wagons kept the old body style and engine.

[2wagons]

ARCHINSTL, inquiring minds need to know, did you receive the vac advance and EGR modulator? Did you install them and did they make any difference? I plugged my two vac line back into the secondary diaphragm but vacuum losses made the idle rough so I plugged them back up. One hose had 15 inches vac on it at idle.

[ARCHINSTL]

2wagons -
Yes - I installed the OEM EGR modulator and the OEM 3-tube distributor vacuum advance yesterday. And they work !
The idle has smoothed out considerably - and - for the first time I get the basic timing at 5 degrees plugged and it now advances to the prescribed 13 degrees with all lines attached. I also now get the "low vacuum" the wonderful FSM talks about in regard to the EGR valve itself - but I did not actually measure it yet.
I checked the diaphragms of both new units against mine, and the old EGR modulator did have a hole, as it permitted air to enter the "chamber" at all times. The upper distributor diaphragm also had a hole, as neither tube would hold a vacuum or advance the little lever. I have not disassembled either to see if they can be fixed; I will attempt that later this Winter. I do have my doubts on whether the distributor can be fixed by an amateur, as it is really clamped/crimped, but the EGR modulator may be a different story; we shall see.
I suspect that more of my problems were caused by the EGR thingie than the other, as the centrifugal part still worked.
Tom M.

[takza]

The upper distributor diaphragm also had a hole, as neither tube would hold a vacuum or advance the little lever. I have not disassembled either to see if they can be fixed; I will attempt that later this Winter. I do have my doubts on whether the distributor can be fixed by an amateur, as it is really clamped/crimped, but the EGR modulator may be a different story; we shall see.

With the dist...might be able to grind away the crimp...fix the diaphram...solder or epoxy it back together? Considering the cost...might be worth it?

[ARCHINSTL]

takza -
Thanks for the tip; I had not gotten far enough to think of grinding the crimp. This makes more sense than attempting to bend/curl the crimp.
It would definitely be worth it.
As mentioned, this will be a Winter project.
Tom M.

[2wagons]

Hey ARCHINSTL,
Now that you have the new parts in for a coupe of weeks, what is your gas mileage and performance like? any changes for better or worse?

[ARCHINSTL]

The gas mileage is unknown at this point, as I've not run a full tank through. It was 27 +/- before, though, in suburban driving only.
The performance improvement is minimal, although it is somewhat smoother. Not as much improvement as I would have thought, though???
However - probably unrelated - my "surging" or "loping" when warm is back. Rev to 2200 and it drops back to 1800 then up again to 2200 and repeats itself. Guess there is still a vac leak somewhere...
Tom M.

[waynehoc]

Thought I'd jump in on this thread as I've just replaced the vacuum advance in my '87 FWD Wagon, which seems, initially, to have solved TWO problems.

Background - originally found this site while looking for clues re engine backfiring on deceleration or when revving engine quickly in neutral and letting foot off the gas quickly. As well, had an annoying low to mid-throttle surging/hesitation problem. Also had a problem where it seemed the engine was running a bit warmer that I thought it should; at freeway speeds (100kmh) and fairly cool temps outside (± 10C = ± 50F) the temp gauge was running at close to the 1 o'clock position, and with the same outside coolish temps idling in traffic, the same 1 o'clock position on the temp gauge with the rad cooling fan coming on all too frequently.

At first I thought I had two different, unrelated problems. First went after the cooling situation, and pulled the rad and backflushed it, and did a coolant flush and fill. This did seem to help a bit, but did not totally get rid of the problem, so I started thinking about getting a new two-row all-metal rad after reading all the cooling posts here. In the end, as we're now into Winter, I decided to let the cooling thing go until Spring, and concentrate on the backfiring.

First, right away confirmed that the AAP diaphragm in my carb was fine - held/holds a vacuum with no problem. Functions fine as per the FSM.

Next started researching the backfiring problem intensively on the Internet, and started finding references to ruptured vacuum advance diaphragms/improper ignition timing, and also discovered what retarded ignition timing does as far as being a major contributor to engine overheating. Now I figured I was on the right track to maybe solving two problems with one solution!

Next I checked the timing on the 3A-C, and found that while it was right on at 5 degrees BTDC with vacuum hose pulled and plugged, that it only advanced to 7 degrees BTDC with the vacuum hose reconnected. So, got a longish length of tubing and did the suck test on both vacuum advance diaphragms and found they were both leaking - neither would hold a vacuum.

Next step was to order a new rplcmt vacuum advance unit, but only after going to a few local wreckers and checking out close to a dozen and a half units, that they all were bad, so I concluded that this vacuum advance unit is a weak point on the 3A-C. First tried the local aftermarket suppliers such as Lordco, T&T, etc., but was either not available, or available at a cost of $230CDN with a two week wait to bring it in. Toyota Canada could supply the oem unit, but for $243CDN! So the on-line search began - I ended up getting a Standard Motor Products p/n VC360 aftermarket unit from Rock Auto for $87.79USD + shipping, taxes, etc. As I'm in Canada, it ended up costing me close to $190CDN, but that was a far cry from what Toyota wanted, or even T&T. Shipping, via Fedex Air (the only option I was allowed to ship to Canada), was the big $$$ killer.

Yesterday, I installed the new vacuum advance unit, checked the timing (timing is now correct as per the FSM at 5 degrees BTDC with vacuum hose diconnected and 13 degrees BTDC with vacuum hose connected), and adjusted the idle (was able to turn the idle adjusting screw out (= lower idle speed) by close to one full turn! Seems the previous 'mechanics' who worked on my wagon simply turned in the idle screw to compensate for the problem. Another little backgrounder - just recently got back into doing my own repairs again after an almost 10 year hiatus due to family/work/time constraints.

Initially, the car idles smoothly now at 800rpm with no missing like before (must have been the vacuum leak from the bad diaphragms). Also, the surging and hesitation seem to be gone/almost gone, and the temp gauge is running steady at the 12 o'clock position driving around town at modest highway speeds. Too early to know for sure about all these improvements, and very curious to see how my gas mileage will change/improve. Will post back later after I've gone through a tank or two of gas.

Here are a few pics I took



Note that the VC360 is 'Made in Japan'



Note the orientation of the vacuum ports, and that there are 3 ports on the new unit (one for Federal vehicles with HAC). I did not require this 3rd port, so just capped it off. Note also the ND (in the small circle at the 6 o'clock position on the metal face) on my old original oem unit to the left; the new unit to the right also has ND on it, in the same 6 o'clock position, but can't be seen in the pic. Both are mfgd by Nippon Denso!



Note that the units have the ports aligned a bit differently one from the other. This was not a problem - the vacuum hoses with the new unit installed simply connected at an angle pointing more closely to the firewall in my vehicle. Plenty of clearance there so was okay.



Note that the 3rd port (for Federal vehicles with HAC) is an orificed port. I capped this port as it is not required for Canadian wagons.



Pic of the distributor on the engine - I did the job without removing the distributor. Note the capped HAC vacuum port on the vacuum advance unit. To get enough forward movement of the breaker plate (with pick-up coil) I simply removed the retaining snap ring - seen at centre of distributor rotor shaft. This forward movement is necesary to disconnect the arm of the old vacuum advance unit from the pin/lug on the breaker plate and connect the new vacuum advance arm.



Pic showing the snap ring removed and laying loose on the rotor shaft. There is also a washer behind the snap ring.

[ARCHINSTL]

waynehoc - Good writing and XLNT photos !
I had the same result when I installed a new vac advance with overall running and the advance settings being correct for the first time. I'm glad you noted that you tried a number of "previously enjoyed" advances which did not work. That made it easier for me to justify my purchase of a new one. The advance did nothing to relieve my surging/hesitation, though; that was related to the "A" vac switch and its effects on other systems. Your Canadian vehicle may or may not have this switch, depending on the transmission.

I did note a wide disparity in pricing:
Yours from Rock Auto - - - - - $ _88CA / $ 76US
Advance Auto - - - - - - - - - - $ 123CA / $ 106US
Mine from Butler Toy (IN) - - $ 139CA / $ 120US.....(free freight, though);
Local STL Toy dealer (Fusz) - $ 155CA / $ 134US
Toy Canada- - - - - - - - - -- --$ 243CA / $ 209US

Tom M.