Fast Idle on 3F in an FJ75

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petefj75

petefj75

Joined
Mar 12, 2018
Threads
2
Messages
5
Location
Australia
So I have a bit of an issue with fast idle on my '88 FJ75. I think I have tracked the problem to throttle sticking. What happens after the engine is warmed up choke off etc. The idle returns to around 1200. After giving the throttle a little blip it drops right down to normal idle speed.

The throttle cable has some slack in it when idle to I am (reasonably) confident it is not the cable.

What I have noticed on this side is that there is a little play in the shaft that goes into the throttle body (not sure if that is normal).
CARB1.webp

So if I rev the engine and it it sticks idling faster. Then I give it a little tap right on the end (ie no twisting it) the idle drops back to normal.
carb2.webp

So I am thinking that is what is sticking.

I have already tried spraying carb cleaner on the outside and also down the throat. It helped a little.
I haven't tried checking for vacum leaks.

I'm not the experienced fixing stuff on cars, so I am looking for a few ideas of what I can try. Thanks
 
I would ask this question in the 60 series forum where you are likely to get more eyes on it from people that actually have a 3F.
 
My 3f does this as well. I squirt wd40 on the butterfly hinge bushing and it fixes it for a few weeks.
Eventually I put an extra spring, and it cured it. It was only a very light spring. hardly noticeable on the throttle pedal.
 
You would need to inspect the butterfly when it happens. If you pop the carb top off and actuate the throttle under the hood, see if the butterfly is sticking when the hang occurs. If the butterfly closes completely and the idle hangs, it is most likely a vacuum issue. Grab a vac gauge and measure at idle when hot, see what it says and report back.

If the butterfly sticks and requires manual actuation to close, then it would be best to rebuild and clean the carb out.
 
44Runner said:
I would ask this question in the 60 series forum where you are likely to get more eyes on it from people that actually have a 3F.
Click to expand...

The American 60 series carbs are different to these.
 
The other place to check is the spring under the accelerator pedal rod. I know you are seeing something on the carb, but the spring has probably lost its ability to bring the cable fully back to idle, that's why the blip on the pedal brings it back .
I had this exact problem and it was fixed with the $10 spring from Toyota after advice from other MUD members.
When there were lots of 3Fs around, this was a common problem.

Part number, common to all 60 and 70 series I think 90508-29017

 
Last edited:
I have eventually looked at this again, after what @mattressking said, I've seen that the butterfly value moves when I give it a tap to return to normal idle.

I have played around with some spray carb cleaner targeting the throttle body and values and it did make the problem go away briefly. So it problem needs a rebuild (or maybe an upgrade ;) ).

I will probably given the spring options mentioned by @roscoFJ73 and @pithicus a go first, either the return springs will probably help.
 
Have you tried pulling that accelerator lever back when it idles high? (the one in my pic)
 
roscoFJ73 said:
The American 60 series carbs are different to these.
Click to expand...


they are, but prone to the same issue. I am one of 5 members currently dealing with similar scenarios with OEM 2F carbs. I am also highly suspect of the butterfly getting hung on the inside of the carb bore...funny thing is, I was thinking about going to a 3F carb to eliminate this, but maybe not...
 
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