fast idle

[xirdneh]

What controls fast idle? Is it all mechanical or does one of the vacuum hoses play a part? I'm having some problems with three Tercels in this area. Two cars will not start on cold mornings unless primed or the fast screw cranked way in.
On the third car cranking in the fast idle screw does not do anything (not even increasing the idle speed).

[splatterdog]

Controlled by the choke coil and the high idle cam. The cam has 3-4 steps that the high idle screw hits.

Choke flapper on top of the carb snap shut when throttle is opened on a cold engine?

[Petros]

a vacuum leak will make it idle fast, and make it hard to start on cold days (because it leans the fuel air ratio). You will never get the idle down unless you find and fix all the vacuum leaks. Check for that first (lot of threads on that topic, do a search). Than you can adjust the cold idle and the warm idle (they are different adjustments). See the FSM for the procedure, it is simple enough.

[splatterdog]

a vacuum leak will make it idle fast, and make it hard to start on cold days (because it leans the fuel air ratio). You will never get the idle down unless you find and fix all the vacuum leaks. Check for that first (lot of threads on that topic, do a search). Than you can adjust the cold idle and the warm idle (they are different adjustments). See the FSM for the procedure, it is simple enough.

Not necessarily so. Typically only fuel injection will idle fast with a vacuum leak. Unless your carb is beyond richness requirements a vacuum leak will only cause rough running. Since they require priming to start that is likely not the case. Accelerator pump could be weak too. Should get a strong squirt at the top of the carb throat when throttle is applied. I just fixed an old ford 460 that wouldn't cold start at all without pouring gas down it. Turns out the last person to touch the carb left out a check ball and a no longer available retaining spring on the accelerator pump intake port. oops

Nevertheless, checking for vacuum leaks is the first thing you do to a terc. Vacuum is only used on the choke as a pull off(opens the choke plate slightly after engine starts)

The best thing for a fussy aisan carb is a weber! I hate to admit defeat, but I don't get paid to work on my car and it takes away from time I can get paid. I was so happy the first time, it was one of the first things I did to my $100 parts car(sold my nitrous system for that one). Didn't need it nearly as bad as the first one, but I have no regrets. Now I only have slight difficulty starting when it's sub zero and mileage never get below 30mpg no matter what.

[Paul]

Don't forget to check the TVSV. When it starts to flake out, it takes forever to get off high idle.

Paul

[splatterdog]

Just for clarification, too much idle or not enough?

To me it sounds like not enough, it was said screws were all the way in with no change.

[xirdneh]

one of the cars is my aunts so i drove it home after work. something was keeping the gas pedal from going down all the way. removed carb and the problem was the fast idle cam (i guess thats what it is called) the arm from the choke is connected to it. the bolt holding it was very loose and backed out far enough to block the throttle linkage plus the fast idle screw was rendered useless from misalignment. i corrected the problem and hopefully that will solve the hard starting in the morning.
probably will not get to the other car for a while

[takza]

Check that "idle" screw on the front of the carb...the diaphram used to control return to idle? Problem is that you can't get to it with the air cleaner on. I also added an additional spring inside the OEM throttle return spring.