Didn't know the site is back online! Just walked in from a carb tune up...
I don't have any specialty tools for RPM measuring, The toyota was stalling out at red lights so I read the manual and after working up a little courage decided I'd go for it.
I took the aircleaner off plugged the hose on the bottom and situated it so that the hose was still reaching the top of the engine.
Then I took off the choke assembly. I didn't have a way to test continuity But I think that is one of my problems. When Starting up on a cold michigan morning I push the gas pedal a few times and turn the engine over. IT sounds PURRRfect. Until 30 seconds in and then it starts sounding a bit choppy. Oh well I go inside get my gloves, pour my coffee into my stanley thermos kiss the lady goodbye and come outside to see my beauty warming up. And I get a little warm inside too! When I walk a little closer though... She gets a little too excited and starts over-revving!!! I sit in the cockpit and just barely touch the gas, and the choke disengages and comes down to perfect Idle... Driving down the road some more and hit a red light and the idles too low and she threatens to stall! If I park to go into the gas station and fill up after 10-15 minutes then start up choke gets stuck and I can't unstick it by tapping gas pedal. Thats where I was when I decided to attempt the tune up. So I take off the choke and reset it best I know how just so there is slight play on the choke plate. Then I fire up and after warmed up I tinker with the idle screws on the front and side, I think its idling a little high right now, so I'll dink around some more tomorrow. Anyhow if there is any advice to give a guy with limited tools and mild knowledge let me know. The guy I bought it from put a new CV axle on her and said he re-timed the engine I red the checklist too so I will try to use that knowledge I have acquired from that... But I might add that the fuel economy is not what it once was... Replaced the spark plugs and have been keeping up on oil changes etc...
check for vacuum leaks first. while the engine is running, spray carb cleaner where the intake manifold bolts to the head, the base of the carb, the throttle shaft, etc. also suck on all of the vacuum diaphragms and make sure you can't suck air through them. if you can, it's busted. make sure the hoses are correctly routed. rule all that stuff out first before adjusting the carb settings.
The fast revving is normal, and is actually the fast idle, factory set for 3K RPM. Usually on a cold start it takes mine up to 30-60 seconds before fast idle kicks in.
Former Tercel Enthusiast (not a practical family car anymore but they still have a place in my heart)
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sounds like it just needs some adjusting. AS DLB pointed out, check for vac leaks first. you will never get it to idle properly, cold or warm, if it has vacuum leaks, the timing is wrong, or if the vac lines are misrouted. It will not cost you anything to check and adjust everything, it is best to do it yourself since most repair shops do not have any mechnics that know how to work on these carburators (most have never even seen one). It is not hard, just work your way thought each item. You have to check those in this order:
1) inspect each vac line from each end, compare them with the vac routing diagram for your car. look for mis-routed vac lines, any unplugged ones, and for cuts or cracks in each of the lines (do not be intimidated by the number of lines, take them one at a time with good lighting and the vac diagram from the service manual, it will only take about 10 to 15 min to visually inspect and check them all).
2) if those are good, than check the carb mounting nuts (there are 4, at 12 mm, require a 12mm socket and a long extension, make sure they are snug down, no need to over tighten), and the intake/exhaust manifold bolts (14 mm, will both an open end wrench and a socket wrench with a long extension, get them fairly tight-you will not be able to reach all of them, just do the ones you can reach).
3) Than do the vac component test as outlined by DLB above. If the Auxiliary Acceleration Pump (AAP, see the vac diagram) line is full of gasoline, cap off both ends (it will run fine without it. If the distributor vacuum advance is leaky cap off the lines to it (again it will run fine without it).
4) Rent a timing light from an Autozone or Oreilley's (it is free, full refune when you return it, other local parts store chain may have similar deal), and check the spark timing with the vac lines off and capped, set it at 10 deg BTDC (not the factory 5 deg BTDC), see the factory service manual on how to set the spark timing (not diffcult, just takes a 12 mm wrench and the timing light), set it as a slow but steady idle if you have no tach.
5) with the car cold, set the fast idle on the throttle plate (see the manual for the location of this, it is on the crank assembly where the throttle cable actually attaches to the carb throttle shaft, it is the smaller diameter screw that moves with the throttle shaft. Set it so it cold idles upon start up in the 2000-3000 rpm range. Than set the warm idle after it warms up and the choke is fully open (you should also check to verify the choke is closed when stone cold, and that it opens as it warms up, easy check). the warm idle is the largeer scew on the carb body itself that pushes on the throttle crank where the cable attaches to the carb, but it does not move with the throttle shaft like the fast idle screw. Set it so it idles a bit high, I like 900-1000 rpms (rather than the factory 600, which usually allows it to stalls out in cold weather).
6) if it will not idle down, check the throttle positioned screw. it is on the other side of the carb from where the cable attaches to the throttle shaft. It is an adjustment that prevents the throttle from closing too fast to keep emissions low (when the throttle slams shut it could cause a spike in emissions, this slows the last few degrees of throttle closing to prevent it, you will not notice it if it is adjusted correctly, too much or too little could affect drivablity). Sometimes people not knowing any better screw this down way too far and it will not allow it to idle down. this crew it should be adjusted so it just touches the throttle shaft assembly during the last 5 degrees or so of throttle travel, and than back away from it so it does not touch the throttle shaft assembly.
Usually that will solve idling issues, if not it may need something else like a carb rebuild, or to replace some faulty components.
Let us know what happens, if you fixed it or if you get stuck and we will help you out again.
Something minor, but you might as well check it.
The throttle cable may needsa little bit of slack.
Also, remove the cable, raise it high and dribble silicone lube in it until it runs out where it attaches to the accelerator shaft inside (put a rag down to catch the drips).
Not a bad idea for everyone to do it annually, either.
Tom M.
T4WD augury?
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