sharkblue

Hey guys ive got a 88 22R 2wd pickup i just purchased. However im having some issues with it. It fires up but will not idle unless you continusly pat the gas. Ive changed the plugs, wires, cap, rotor, fuel filter, oil, and the other usual things. When starting it up she turns over and runs as long as im patting the gas, but not to much. If i press the pedal down and hold it, i hear a sssshhhhh sound and it will stall. I can rev it up and it sounds fine as long as i pat the pedal. No black smoke or any smoke actually coming from the exhaust, and i havnt gotten to check the timing b/c it wont idle long enough without stalling out. Im somewhat familiar working with carbs, ive worked on my motorcycle carbs when i bought it. but by looking at the carb from the front the plate on the right side (choke plate?) is almost completely closed and closes more if you press the throttle, but the plate on the left is wide open and moves very very little. This just doesnt seem right to me but i could be wrong cause i know little about these carbs. It is time for a new carb or rebuild this one? BTW the truck had been sitting a couple years before i bought it. Thanks

kyle_22r

if it won't idle on its own, i'd start by checking the fuel cut solenoid. it's on the back side of the carb near the choke housing, and has 2 wires coming out. have somebody turn the ignition on while you listen by the carb, it should make an audible click. if it doesn't, it's either not getting 12v power or its fried. what it does is shut off the flow of fuel to the idle circuit when the ignition is off to prevent dieseling.

the thing with the secondary choke plate is normal. it's not a real choke plate, it's actually sort of a half mechanical/half vacuum secondary setup. the secondary throttle plate is opened directly by the throttle linkage. however, that choke flap is attached to a metering rod that meters fuel to the secondary jet. when the pedal is mashed to the floor and the secondary throttle plate is opened, the choke flap is drawn downward by the vacuum and increases the fuel richness of the secondary jet. kind of a strange scheme if you ask me, but it (usually) works in the end.

surf4runner

rebuild it if its been sitting. bad gas? clogged idle jet or fuel filter? timimg? can be set w/o the engine running.
what carb? a 2bbl progressive carb will open one side and then the second
idle adjustment? set it higher and then see if it idles.

sharkblue

thanks for the replys, ill check the fuel cut selinoid tonight, I was thinking about rebuilding the carb any just to get it nice and clean so i will probably do that this weekend. Ive messed with the idle adjustment screw plenty, doesnt matter where its set, still stalls. We drained the gas that was in and filled it with fresh gas.

how do you set/check the timing w/o running the engine. I have a shop manual (haynes i think) but they say you have to run the engine to check it. Thanks again

sharkblue

Well the Fuel cut is getting power and im hearing it click so that seems ok. Im gonna rebuild the carb and replace the vacumm lines this weekend. Thanks again

surf4runner

set #1 to the timing mark on the pulley (~10*? BTDC) to make sure its close.
a running engine will include the advance and idle speed

thetundrawolf

I really need help with something...

My secondary choke plate mechanical linkage is *gone*.

I had the plate wired wide open, but this affects the metering rod.

I need to know, what is the best way to put this carburetor back together without the mechanical linkage? Just leave it as- is? Will my fuel economy suffer?

I really need help on this, I am leaving Friday to go camping.

slow-mo

Are you saying that the mechanical linkage from the Primary Throttle Valve to the Secondary Throttle Valve is gone? Or the linkage from the Air Valve to the Metering Rod is missing?

thetundrawolf

I am missing the external linkage that travels down into the linkage assembly on the side...

The air valve is connected to the fuel metering rod.

The linkage arm that connects here (Circled)



You can see it better, here:

slow-mo

OK, I see. Remove that wire holding open the Air valve.

The Air Valve is design to open automatically open under pressure differential when the secondary throttle valve opens. The Air Valve will rotate independently of the rod linkage that is missing.

When the secondary throttle valve is closed, the linkage holds the Air valve partially open. When the secondary throttle valve opens, the linkage will allow the Air Valve to fully close. Then vacuum (negative pressure) is formed under that Air Valve from engine vacuum. The higher atmospheric pressure (above the Air valve) will force open the Air Valve. The greater the vacuum under the Air valve (how much the secondary throttle valve is opened), the greater the Air Valve will open.

Because the secondary barrel has no venturi, Aisan designed this Air Valve system to operate as a variable venturi. Not a true variable venturi but something like a hybrid.

You should still scavenge these two linkages from the junkyard, if possible, to fix your carburetor.

thetundrawolf

Thank you SO MUCH for this information!

I have one more question, why does it hold the valve partially open when the secondary valve is closed? Is there a reason for it to be open? Or is it just locking it in place, so it doesn't open any other way?

Okay two questions, how will not having that linkage affect my fuel mileage if I just leave it to open under spring pressure...

slow-mo

Your welcome.


For this question, I do not know. I have no clue. Toyota (Aisan) does not state specifically why it is designed this way.

If you mean by leaving the Air Valve open, as it is with it forced open?

Even though the secondary Metering Rod has lifted off the secondary Metering Jet, there is still no vacuum produced as long as the secondary throttle valve stays closed. The gas wont go anywhere.

With the Air valve locked open, the secondary throttle valve acts as a door between atmospheric pressure above it, and therefore the fuel that would normally flow out of the Secondary Main Nozzle, and the vacuum below it. In order for fuel to flow out of that Secondary Main Nozzle, it would need to subjected to pressure differential, a.k.a. vacuum.

I hope that answers your second question.

thetundrawolf

That makes sense. Just wondering about the purpose of the linkage...

slow-mo

The only thing I would say is that the power made by the secondary throttle may either come late or may be poor because there is not enough vacuum created for the fuel to flow out of the Secondary Main Nozzle. That's why I was saying to remove that wire holding open the Air Valve.