High Idle staying up too long...TURTCEL

[TURTCEL]

What component on the carburetor do I adjust to get the high idle to not stay up so long? It seems to stay on longer than it should even on warmer days.

I know the carb choke system is step down process but when I tap the gas pedal to drop the RPM's once it has run for a bit on high idle it revs high but then won't drop off much. The car needs to be almost totally up to operating temp before I can get the high to drop to 800 RPM's.

I had an '84 Yota pup and the carb never did this, I could get it to drop off by tapping gas pedal even when totally cold. Just seems like I am wasting a bunch of unecessary fuel.

I have looked at the carb section of the FSM and searched for choke adjustments but haven't found exactly what I am looking for, that I know of.

Peace

[dlb]

check page 21, aka MA-10 for how to adjust the fast idle. super easy, only takes a few minutes.

[TURTCEL]

The idle is set ok for high idle. It is like I can't tap the throttle to get the choke to pull off. It stays up and needs to be warmed up all the way to get it to drop down.

I think it is one of the choke components that needs adjusting but there are a few different choke coontrols. The choke opens all the way once warm but seems on be on too long.

Any thoughts?

Peace

[dlb]

the fast idle also controls the step-down cam that lowers the idle as the car warms up so that's why i suggest looking at it. the automatic choke is not adjustable on the federal cars, and the choke opener and choke breaker are used to open the choke valve a little bit at cold and hot settings, so i can't imagine it being one of those unless you have a vacuum leak in the system that is being routed through the TVSV so that it only occurs when cold. maybe check the resistance on the automatic choke. i guess if the resistance is too high, it will take longer to heat up and open. i think it's supposed to be between 11-13 ohms but check the FSM.

[Petros]

You got good advise on the fast idle, but you also might check the adjustment the device that is opposite the throttle cable bell crank that holds the throttle open momentarily to prevent it from slamming shut. If the adjustment is too much it will hold the idle open too high for too long. Also make sure the diaphragm that is connected to it has the proper vac sourse, if it is connected to the wrong vac source it will hold the throttle open.

And of course, check the whole system over for vacuum leaks, which could cause a fast idle.

[TURTCEL]

Thanks for the responses guys.

Do I understand it correctly that in order to completely adjust my carburetor I need to start by doing the procedures in the FSM on FU-25 thru FU-27 ; then set my idle mixture; and then finally go back and do the procedures on FU-26 thru FU-27?

Or can I do the procedures on FU-25; then set idle mixture; and finally do procedures on FU-26 thru FU-27?

It is a little confusing the way I read it but I think that by intergrating the adjustment of the idle mixture is the reason for the change in procedure steps.

Peace

[Petros]

yes, and make sure you have no vacuum leaks, that will make it idle too fast as well, and none of the other adjustments will be correct if you have unmetered air leaking into the intake system.

[TURTCEL]

I definitely have no vacuum leaks on the car...I have checked multiple times but it never hurts to check again. I will do so before setting the carb.

Were you saying yes to the first or second listed procedures in my post? There are 2 different processes and not sure which one to go with.

Peace

[TURTCEL]

So I tuned my carburetor today per the FSM and found the high idle to bet 300 RPM's too high so I readjusted. And the TSV was also 300 RPM's too high so I readjusted that as well.

After that I took it for a drive and it seemed to have a little hesitation so I went back and set the idle mixture to 3 1/4 per the FSM and went from there. At first it ran really chuggy so I reset the idle and started my mixture adjustments from there. I needed to richen the mixture a little to get it to run the smoothest and since the test drives it seems to be running really good.

I will see how the idle is tomorrow morning in the cold and see how long it stays high for.

My main concern with needing to tune the carb is that shops don't do all the procedures, they just get it to run as good as they can. I also think my fuel mileage is not what it should be so I will start monitoring it from here.

Thanks again for all the help.

Peace

[dlb]

just reading a bit more of the FSM on the choke system and thought of something else. if your TVSV is original, it likely has trouble reaching or doesn't even reach the 3rd heat stage. it's only once the TVSV reaches this stage that it engages the choke opener, which in turn releases the fast idle to the third step. you might want to test your TVSV, as well as the choke opener.

[TURTCEL]

just reading a bit more of the FSM on the choke system and thought of something else. if your TVSV is original, it likely has trouble reaching or doesn't even reach the 3rd heat stage. it's only once the TVSV reaches this stage that it engages the choke opener, which in turn releases the fast idle to the third step. you might want to test your TVSV, as well as the choke opener.

Actually the TVSV is new from Toyota about 2 months ago...I broke a nipple off of the original when replacing all the vacuum lines. The choke opener is also ok.

Turns out that the reason I was having adjustments issues was because I was adjusting the carb while it was set at 10 degrees BTDC. I reset to the stock 5 degrees and readjusted the carb.

I got my idle adjustment back and the mixture screw only had to be richen about 3/4 turn to get the best runnability out of the car. It was about 3 turns out beyond the initial 3 1/4 setting at 10 degrees...way too rich.

I reset the timing to 7 degrees after the carb ajustments and it is running much better now and I should be saving a lot of fuel.

Thanks for all the advice.

Peace

[TURTCEL]

So I did some more carb adusting and got the car running really well but I still had some concerns. I felt like the mixture screw was turned out way too far and causing the car to run too rich at idle. I initially set the mixture screw to 3 1/4 turns and went from there. Eventually it was aroung 6 full turns out...not right but ran well.

It was my understsnding that as I turned the mixture screw out it would raise the idle speed to a point that it would not raise anymore and then I would readjust the idle screw to lower it down. I kept doing this but eventually lost all my idle adjustment at the idle screw. Couldn't figure out what was going on so I left it for the night.

I reread the FSM and watched a couple of YouTube vids on mixture and idle adjustments...ding ding ding it finally clicked with me. I was confused about the lean drop and now I understand it.

****Petros**** Thanks for the PM on my carb question...it really helped me get past my silly mind block on understanding the adjustment process.

I was adjusting the mixture screw out till it ran smooth and then kept turning it out, raising the RPM. I will recheck my timing and reset my mixture screw to an initial setting before I reset my mixture. What I need to do is lean it out till the RPM's rise and then eventually drop to find my lean drop and then back it off about about a 1/4 turn or so. I will then readjust my idle speed and continue to lighty fine tune the carb till I find the perfect spot.

I really want to thank everyone that has ever responded to my posts with helpful tips. This website is super cool and I really enjoy working on my car. I think my friends think it is always broken down because I keep working on it but that isn't the case, I just like to tinker. It has been driving my wife crazy because she wants the car back to drive but at least this gives me an excuse to drive it myself. HAHA.

Peace

[Petros]

there is not really a straight forward way to adjust everything in sequence; when you change the mixture it changes the the speed the engine runs, it changes the speed of combustion, and the speed change also changes the vacuum in the manifold, and so forth. So that means you have to go back and fourth between idle speed and mixture, than back again in an "adjustment spiral" until you get everything in balance running at the correct idle speed. It is not so much a problem when you can not adjust the mixture in the factory sealed carbs, but "back in the day" when all carbs had an idle mixture screw, and some even had mixture adjustments for the whole range (like the wonderful old SU carbs from England), you needed to be aware of how when you change one adjustment, it would affect everything else. That was when true engine mechanics really had to understand how the car worked. Now they depend on the computer doing everything, and the "test" is just a "go./no go." on each part.

I keep having fantasies of owning one of those per-regulation "B-S" (before smog) cars where I can fiddle and tweak the systems to my satifcation and NOT break any state or federal laws.

[TURTCEL]

So I got my carb tuned and the car idles very smooth and accelerates and drive sweet...but. My issue now is that when I go outside to start the car on a cold day or even in the low 40's I can't seem to get the car to start and run up to a high cold start idle if I tap the pedal twice before starting.

I tap twice, start it, and it starts then dies. I have to retap the pedal 4 or 5 times to get it to start up and even then it is boggy and I have to keep my foot on the pedal for a little bit. I know the oil is cold and oil pressure needs to build a little for the car to start up and run but I only have this issue now that I have adjusted the carb when the car was at full operating temp. All hoses have been reconnected and no vacuum leaks.

I set the throttle positioner to 1400 RPM's per the FSM and the high idle speed to 3000 RPM's per the FSM. My car is a MT with P.S. so the specs were set to those requirements.

Any idea why the cold start is going like this? Is there an adjustment I can do? Are the specs in the FSM where I should be setting the carb since the car is not new anymore? I figure the FSM is for brand new cars so maybe a car with some wear on it may need to be set a little different. The car starts up fine as long as I plug my block heater in over night and the coolant is a little warmed up. But a low 40's I would think the choke would do fine itself with out the block heater plugged in.

Any suggestions?

Peace

[Petros]

we also run on crap federal gasoline that is different from what this car was designed to use. Very cold weather is always trouble some with carbs, the crappy fuel does not help (the ethanol content attracts a lot of moisture out of the air and in a cold engine it tends to ice up in the carb).

Best bet is do two things: push the throttle all the way to the floor twice before you start (not a tap, but a push to the floor), and than after it starts, hold the throttle open well above the fast idle and give it several slow but high rev blips, two or three usually does it for me. Than it will run normal after that. And of course the longer it warms up the better it gets. But I have found even when in good tune, that in very cold weather, it takes just a few higher rev blips for about 10 to 15 seconds, and it will be better behaved after that.

good luck.