RPM Cycling Situation & Vacuum Switch Location Query

[sdoan]

I had blown out the canister-to-tank tube and also attempted to draw a vac on it, until I remembered that it should be open at the tank. I had not considered a leak in this tube. I had renewed all three of the fuel hoses at the tank three years ago - guess I'll try to remove a hose and plug the steel tube and try to draw a vac at the front.

It sounds like you've already done the test I was thinking of. I didn't mean to send you on a wild goose chase - while I've done a lot of mechanical things I've never had to mess with the charcoal can so really don't know the details of it's operation. Thinking about it it seems that the tube to the tank should be open and I don't know how the engine could "sense" a difference between open in the tank and open to the air.

My charcoal can has a vacuum valve on top that it look like it could stick open and result in an air leak - I'm betting you've ruled that out already.

Is it possible to remove the tank, submerge it and pressurize it to look for bubbles? (Showing my ignorance again? )

Good Luck,

Shawn

[keith]

I think that FSM's get worse with newer vehicles. My Saturn"s FSM comes in 6 volumes and has even less information than the Tercel's. To replace the intake manifold gasket, you need about 4 bookmarks because the information is not all in one place. All in all, its really not a bad manual. I used it a lot.

[ARCHINSTL]

Well - I'VE HAD IT WITH THE AISAN !!!
The RPM cycling defeated me - I checked every single stinkin' gizmo in the entire emission, electrical, and fuel system, and every single stinkin' one checked out OK, whether from an electrical or vacuum or function standpoint.
I blew out/sucked on the lines from and to everything (all hoses were replaced, yet again).
There are no vac leaks in any part of the plumbing, whether manifolds, distributor, switches or the steel spaghetti.
Everything - and I do mean everything - checked out within FSM limits using the vac gauge and a multimeter on switches, sensors, and solenoids. Everything worked as it was supposed to. Everything was attached, with no loose, corroded, or otherwise errant wires, connectors, fuses or grounds.
My results on testing everything in late '08 matched those of earlier '08 and those of late '05; nothing is amiss. Right...
Of course, the ECU itself cannot be checked as there are no specs in the FSM about it nor, in fact, ANY info in the FSM about it. All I can figure now is that the ECU is (at least) partially dead.

I ordered a Weber.

And so the journey begins...

This thread has had an inordinately long life with an inordinate number of visits - Amazing!
I hope others can benefit from it, and I DO thank all who have helped!
Tom M.

[xirdneh]

but did you at least try switching the fuel solinoids?
cannot explain why but it worked on two cycling tercels for me

my '83 FSM shows them opposite of the carb rebuild kit instructions and some other FSM's

[ARCHINSTL]

Actually - I did switch the solenoids as a last resort two weeks ago, based on your previous notes on same. I did this with the current Aisan with no change. After this, I even switched all of the connectors inside the big green plug to no avail.
I did not do this with the (I think) OE carb back in '05, nor with the first reman carb in '05-'06, nor with the replacement (current) reman carb from early '07 until now.
My reasoning on not trying this before, was that since it affected the OE and both remans, it was not carb, per se, related. Additionally, after looking at numerous 3A-C carbs on eBay and other sites - none had a solenoid arrangement different than mine (and the '85/'86 FSM), ie, two-wire on right rear and one-wire on left of carb.
Yours seem to be anomalies for ? reason...
Tom M.

[scouttster]

Hey Tom-
Just wanted to let you know I have the " cycling problem " too...
Wondering whats the latest?
Thanks

[ARCHINSTL]

Well - the latest is, per my earlier post - I bought a Weber 32/36.
Everything emissions-related is now disconnected, including blanking off the EGR valve.

Honest-to-Gosh, as detailed previously, over the course of three years, I checked and rechecked absolutely-freakin'-everything with vacuum gauge, multimeter and threw everything at it but the ECU - which is a big dark secret, known only to the Mothership, which declined all comments thereon.

The only conclusion I could come up with is that it was somehow temperature-related, as when "A" switch is activated, the signal it sends to the ECU is somehow muddled in the ECU.
I thought for a while it was related to the vapor collection system, as the RPM ranges mentioned in that system's table matched my range as well - also in the secondary fuel cut solenoid...but everything checked out OK with those systems.

When "A" was still electrically plugged but not plugged vac-wise to the carb, the cycling went away - but the rpms did not drop to where they should be between shifts (mind, not screaming, but just not down to where they should be).
Do you have this same situation?

Oddly, while I don't think I was the only one to have this situation in the Club - no one seemed to have the identical prob - or solution. Indeed, I pored over many pages of 'Net Notes on Tercels and Corollas and trucks of that era, looking for clues - and found absolutely nothing with these symptoms - which also seemed (to me, anyway) to lend credence to my belief that the ECU suffered some kind of prob that was unique to my Goldie.

This was the most vexing and frustrating problem I have ever faced with a machine of any kind - and that includes French bicycles....which latter phrase is sayin' a LOT!
Tom M.

[scouttster]

I started off thinking it was a vac leak and changed all the various gaskets like you did. Cleaned the EGR, etc and the problem with cycling ( up and down idling ) or idle surges never went away. Yes, its more profound during low gear changes. After reading all the info in this thread I am convinced my problem is not so different from yours and others. Does Goldie ever stall out while at a stop light or when you come to a stop out of the clear blue for no apparent reason? Then, start her and she turns right over, no problem. Anyway, thats another one of my cars issues..

[gatemaster]

I noticed with mine that cycling occurs below a certain RPM. I think it is around 1k rpm. That still occurs even with the weber. It seems that something senses the rpm. If it is cycling with the fan on high speed at slightly less than 1k rpm I can stop the cycling by lowering the fan speed to med or low. But a slight drop lower in the rpm than it will start cycling again. I have an electric solenoid from a chevy s10 which I can connect to the ac system and mount on the weber to up the rpm when the ac is turned on. I haven't installed that yet.

[Shannon]

I had a surging problem. But, at the present moment I have disconnected the top hose from the EGR to the metal pipe, a short little hose. I do not surge, I think that stopped it. My surge was related to the air conditioning system also , it would stop when the AC was on/off, can't remember which now. I think the manual may show some incorrect emission hose diagrams.
When my fuel cut solenoid went out, the car would just die every time I came to an idle/decelerate/stop, unless I kept it revved up.

[Petros]

Tom,

Did you ever find a spare ECU at a wrecking yard and just try swapping it out with yours? It seems to me it should run with the ECU disabled/disconnected too, but I do not know the details of how it affects the carb.

Also, these carbs can wear internally and suck air in the throttle shaft bore or elsewhere, and it will act like a vac leak. IF that is the case, they can not be rebuilt, the carb has to be replaced.

Good luck with your Weber, probably should have switched to that a long time ago.

[ARCHINSTL]

Well -
First with the Weber: I have not had any surging/cycling probs with it, unlike gatemaster. Note that the ONLY vac connections remaining are the Weber to the lowest dist diaphragm and the manifold gas filter to the front upper dist diaphragm port (rear plugged). The EGR port is blanked off. The O2 sensor is not connected. The H2Otemp sensor is still plugged in. The Weber elect choke uses the same OE connection. The vapor canister is still there, but connected only to the tank (the purge is open to the atmosphere, but I smell no gas). All other vac lines/devices are removed.

Aisan comments:
Preface - MY cycling occurred only from 1800 to 2200 RPM and back to 1800 (could be 1900 to 2300, depending on whether one believed the OE tach or my tach meter). It never occurred when idling - although I did find evidence of the idling cycling on some of the other Toy sites I visited; I never pursued this, save for a cursory glance. My cycling occurred whether revving at a standstill or when under load - partial throttle in traffic was a PITA. My AC is inoperative and the AC idleup thingie was removed and tubes plugged back in '05.

RE Petros - I am convinced it was not from a vac leak. This occurred with the OE (I think) carb, the first replacement reman carb, and the second reman carb (warranty replacement and it was definitely a different carb). It seems unlikely that lighning would strike three times in the same place. I also did all of the recommended leak testing at all other joints, using propane, carb cleaner, and brake cleaner at various times.
I did not pursue replacing the ECU - by this time, I'd had it - plus, I did not want to go to the trouble of ripping apart two dashboards. Since I have not had the prob since the Weber installation, I have presumed it was a fried ECU, particularly as everything else checked out OK a number of times. This would seem to prove that the motor can run w/o the ECU hooked up. However - as far as I know, the ECU is still hooked up electrically, as I did not touch any of its wiring/connections. The only motor thing that I am sure is still hooked up to it is the previously-mentioned H2O sensor. The ECU does affect the OE Aisan carb, as outlined in the FSM, if all else is still hooked up.

RE Shannon - I never tried disconnecting the EGR (with the Aisan) - needed it to pass emissions back in '05 & '07. As mentioned, my surging disappeared with the mod to the "A" switch. I'm pretty sure the FSM shows the correct various diagrams - at least for North America .

RE gatemaster - Do you still have OE stuff hooked up with the Weber? When the blower fan is on at idle/a stop, the RPMS drop as the fan sucks away some electricity and not enough electrons flow to the plugs (tech terms); this happened with all of the various carbs - but no cycling occurred.

RE scouttster - Since you have not mentioned the RPM range, I am presuming that your cycling is the same as mine was - 1800-2200 or so, and not at idling as others have mentioned (as with other model Toys as well). I'd try the "A" switch mod I have mentioned previously. She never stalled out at a stop, save occasionally when it was really cold out and she was not warmed up - but I just cut her some slack on that - I'm old, too... Odd, though - I was having hard hot restarts at the end of last Summer for ? reasons; these were overcome by giving the Aisan some hard accel pedal jabs whilst cranking. SInce that prob launched me into the last go-around with testing every thing (and finding nothing amiss), I wrote it up to bad gas, whether rightly or wrongly (probably the latter supposition, though).

Whew - gotta hit the head!
Tom M.

[gatemaster]

RE gatemaster - Do you still have OE stuff hooked up with the Weber? When the blower fan is on at idle/a stop, the RPMS drop as the fan sucks away some electricity and not enough electrons flow to the plugs (tech terms); this happened with all of the various carbs - but no cycling occurred.

A lot of it is still hooked up. I don't have surge problems. Only cycling of the ac compressor below about 1k rpm.
I suspect a vac leak because I have a hesitation off idle or at slight touch of peddle during slight acceration.
I have not found any vac leaks using standard techniques.

[ARCHINSTL]

gatemaster -
So - it is your AC system that is cycling when the engine is below 1K RPM, and not the engine itself?
I took it that it was the engine doing the cycling - I was wrong, huh?
If so, we have different situations - true?
Tom M.

[takza]

A lot of it is still hooked up. I don't have surge problems. Only cycling of the ac compressor below about 1k rpm. I suspect a vac leak because I have a hesitation off idle or at slight touch of peddle during slight acceration.
I have not found any vac leaks using standard techniques.

The refrigerant is low? Check at the sight glass on the pass side.