How to solve sticky throttle (1 Viewer)

[t00manyuserz]

Posted this in the 80 forum but thought possibly I’d get more experience here since most people with 80s are fuel injected.

I have a sticky throttle on a carburated 1FZ-F. Symptoms are as follows:

- starting the car after it’s been sitting for a while has correct idle at around 700rpm.
- driving the car, the idle will stay at around 1,100 or so. pulling on the pedal will SOMETIMES help, but mostly it won’t go below 1,000. Clutching in will make the rpms tick up.
- if I try driving the car on WOT, the throttle will REALLY stick - clutching in will rev very high.
- with time it’ll sort of return but never below 1,100.

What I’ve done:

- carb is brand new (replaced a while ago)
- throttle cable and accelerator pedal and hand throttle replaced
- tried running without a throttle cable attached - carb returns to normal idle. pushing the throttle by hand revs the engine but returns to correct idle
- reconnecting the throttle cable makes it lazy again

Would anyone happen to have any advice? Could it be one of the round vacuum things around the carb? I haven’t replaced them, could they be going bad? It almost feels like there’s just not enough pull on the throttle cable to release it - and I’m guessing the pull-back is done using the carb’s throttle cable AND vacuum?

 

[mattressking]

Short end of it - you found the fault. Throttle cable disconnected, it returns to idle, with it connected, it fails to return.

Therefore you need to look at the cable you're using, the pedal spring and any hangups in between pedal and cable end. Does the pedal go to the floor then when let off, does the cable retract completely and smoothly?

 

[t00manyuserz]

Short end of it - you found the fault. Throttle cable disconnected, it returns to idle, with it connected, it fails to return.

Therefore you need to look at the cable you're using, the pedal spring and any hangups in between pedal and cable end. Does the pedal go to the floor then when let off, does the cable retract completely and smoothly?

Pedal goes to the stopper on the floor. I have no way of judging how smooth the return of the cable is but it SEEMS okay (it’s brand new and it’s Toyota OEM). So what you’re saying is there’s no vacuum assist or anything like that to pull the cable back? I actually took it out and rerouted it once to see if I maybe did a bad job following its natural bend, but that hasn’t helped much.

 

[charliemeyer007]

I have a cable luber tool made by Yamaha back in the 70's - uses a pee tube and a spray can to wash out the inside of cables. Just because its new doesn't mean its good. This tool will work with stuff like dried grease/crud or lack of lubricant's - will not fix broken wire burrs.

Every cable operated device has a return spring somewhere in the system

https://www.amazon.com/Windance-Motorcycle-Aluminium-Lubrication-Twin-Clamp/dp/B0BKQ4H2PV

 

[t00manyuserz]

I have a cable luber tool made by Yamaha back in the 70's - uses a pee tube and a spray can to wash out the inside of cables. Just because its new doesn't mean its good. This tool will work with stuff like dried grease/crud or lack of lubricant's - will not fix broken wire burrs.

Every cable operated device has a return spring somewhere in the system

https://www.amazon.com/Windance-Motorcycle-Aluminium-Lubrication-Twin-Clamp/dp/B0BKQ4H2PV

Hmm that’s an interesting device. How does it get lube all the way into the depth of the cable though? I’m happy to give it a go if I can figure out the mechanics behind it

 

[charliemeyer007]

The cable is put in the open slot, then the housing is clamped in the open end by tightening the screws. Next the pee tube from your spray can is plugged into the black circle gasket hole on the front. Your cleaner/lube is pushed threw the cable housing with can pressure. My dad thought it was a great design, much better/faster than using a taped up funnel and gravity.

 

[45Dougal]

Another possibility could be that the cable applies some side load on the spindle when it's fitted, causing it to either jam or leak air.
Could try spraying around it with easistart while it's running fast and see if that has any effect.
I'm assuming the carb is bolted down.

 

[t00manyuserz]

Another possibility could be that the cable applies some side load on the spindle when it's fitted, causing it to either jam or leak air.
Could try spraying around it with easistart while it's running fast and see if that has any effect.
I'm assuming the carb is bolted down.

Carb is solid, yeah. I'm going to first try spraying graphite lubricant down the tube, and see if this helps. The main thing was to establish there aren't some peripheral components that might have failed, causing reduced reverse pull on the throttle - looks like it's literally just the throttle cable and the pedal, so I'm going to see if I can do something about it. Hoping it was new old stock that just dried up inside...

 

[t00manyuserz]

Update!

The tool didn’t work for me at all (the spray kept spilling out, I guess it wasn’t latching on properly to feed the spray in) but then I realised all I have to do is just use lots of electric tape to seal it tightly against the cable and go at it.

Happy to report graphite spray worked perfectly - stuck for a little longer while I did a bit of driving but as it warmed up and spread all through the cable, it became perfect. Thanks for the advice. I could’ve maybe even fixed the original cable with this but meh, it lost all its sheathing so it’s a good upgrade for a 30 year old cable