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TR6 Sticking TR6 throttle

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bcbennett

bcbennett

Senior Member
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Hello All,

I had my carbs rebuilt at a reputable British shop. Upon driving home, I noted that my throttle would frequently stick when I took my foot off the pedal, and I would have to "pop" it to get it to come back. Sometimes, it would just rev higher and not return until I repeated the "pop." Very annoying.

When I returned it to the shop, the tech said he lubricated the linkages and it was now fixed. Driving home the second time, I noticed it was NOT fixed. Still sticks open, especially when driving around 60 mph (almost like having cruise control). Any ideas here? Do I need to just further lubricate whatever he lubricated at the shop? There seem to be no impediments to the smooth functioning of the accelerator linkages.

Thanks in advance,

CB
 
Could be an alignment of the linkage. When they are very dry or dirty sometime you'll get a reluctant throttle, but I doubt this is the case here given that you drive/care about here.

Have you checked that the springs are all still attached correctly?
 
CB,

Here is one suggestion. Open the bonnet and operate the linkage by hand. See if it might be binding on the heater hoses that run from the bulkhead to the hose connection at the rear of the block. You may find that the mechanism is rubbing against this hose. I used a zip tie to tie mine back a little bit to stop the interference.

Cheers,
Tush
 
Thanks for these suggestions; I have verified that the linkage is not binding up on any hoses, clamps, or other items, plus I have assured myself that the springs still operate properly. I am at a standstill here.
 
I had a similar problem when I changed the throttle shaft bushings.
They were a little tight around the throttle shaft and that friction prevented the return to idle speed.
I sat behind the wheel and with the engine NOT RUNNING, of course, and worked the accelerator pedal about a hundred times until the bushings "broke in" and the shaft moved freely.
Were the bushings replaced ?
 
BC, Your mechanic was very silly to let you leave with a sticking peddle. I think you may have a off center butterfly or linkage adjustment that is too tight.

Wayne
 
Well, honestly, my mechanic didn't know because it only sticks when I drive in highway mode--getting it up to 60 mph--or else when it's been driving a while and then I rev it past 2000 rpms (when starting or upshifting). When going through low gears and/or starting from cold, it does not do this.

Very weird, no?
 
CB:

I had the same problem with my 76 TR6. What I noticed was that it seemed to stick more after the engine was warmed up. I finally put a stronger return spring on the linkage and that took care of it. Good luck.
 
He should have road tested the car and worked this out before you picked it up. You can lube the mechanical linkage and check the throttle shaft alignment, but in my opinion the mechanic should make this right for you at no charge.
 
OK, I think I have found the problem, but am not sure how to fix it.

The cam that holds the "fast idle screw" is hanging up against the piece of the carb that holds the "idle screw." That is, when the throttle is pressed, these two parts both move and one hangs on the other. How can this happen?
 
The fast idle cam should not move at all with the accelerator pedal.
I wonder if there's been a return spring installed on the choke shaft amd wound in the wrong direction.
If not..
Is the fast idle speed adjustment screw in proper adjustment ?
Is the choke cable adjusted correctly so that the choke is completely off when you push the knob ?
 
throttle.JPG



Well, this is sideways (sorry) but it shows the two parts that hang up. One is the cam with the fast-idle screw, the other is the top-seated idle screw.

Are you saying the piece holding the fast-idle screw should not move with the accelerator?
 
No, I was saying the fast idle cam that is controlled by the choke cable, which is not even in that picture, should not move except when you pull or push the choke knob on the dash. Where is it ? Seems like a portion of it would have shown up in that picture.
Regardless, I think the cause of the hang up is that your idle speed (aka throttle stop) screw (the one with the rusty head) is screwed so far in that it's hanging up on the platform upon which it normally rest at idle.
It looks as though the screw is tightened to the point where the spring around it is almost fully compressed.
You shouldn't have to that much threads showing to get an idle speed under 1000.
 
After Ken has just said. With that pic in mind. I agree and I don't know dungus about carbs. I'd say something is FUBAR and they are trying to circumvent the problem
 
Nelson's photo shows that spring mostly compressed, and I think I can see just a bit of daylight in CB's photo above. So I'm not convinced there is a problem with the idle adjustment.

One question, how did you verify that the binding was at that joint? Does it go away if you hold the vent lever (the one that carries the adjustment screw) in the idle position?

Have you tried smearing just a bit of grease in the contact area? Smoothing the end of the screw?
 
Nelson's photo shows that spring mostly compressed, and I think I can see just a bit of daylight in CB's photo above. So I'm not convinced there is a problem with the idle adjustment.

One question, how did you verify that the binding was at that joint? Does it go away if you hold the vent lever (the one that carries the adjustment screw) in the idle position?

Have you tried smearing just a bit of grease in the contact area? Smoothing the end of the screw?
 

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I can physically see that junction catching and holding things up as I move the linkage under the hood, and yes, if I hold the vent lever, things do not bind. It never did this until I had the carbs rebuilt, so I think something must be different in the set-up.
 
tdskip said:
Agree with Ken and Don.

How about a couple pictures of the carbs in the right orientation?
Click to expand...
I wouldn't mind seeing another picture myself, one where a bit more of the carb can be seen, particularly the choke assembly and the plunger for float chamber vent.
Seeing the shiny freshly exposed threads on the throttle stop (idle speed) screw and the fast idle speed screw seems the adjustments are now quite different from what they used to be.
 
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