PDA

View Full Version : TR2/3/3A Refresh...main reson why idle will lower when kicking the gas pedal?



karls59tr
06-24-2015, 04:13 PM
Seems to me this was discussed before. Somewhere on the linkage? I believe I have the linkage set up fairly well.:confusion:

TomMull
06-24-2015, 04:48 PM
Coulb be set up perfectly but something is sticking. Loosen the center link and see if you can get one to stick by genly operating throttle shaft with you hands. Try moving the shafts horizontally a bit and see if anything seems a bit catchy. If all seems good, it has to be in the linkage.
Tom

TR3driver
06-24-2015, 06:05 PM
Lots of possible reasons. The one that has given me the most trouble over the years is wear in the throttle shaft & bushings at the front of the front carb. With the throttle linkage always pulling downward (to overcome the return springs), both the shaft & bushing wear until they let the shaft droop lower. So if you close the throttle gently (ie normal driving), the edge of the throttle plate hits the bottom of the bore and binds. But if you blip the throttle, the plate levers the shaft upwards and closes against the stop.

Another one that was hard to find was wear in the pivot of the bellcrank allowing the bellcrank to tip far enough that it was dragging against the bolt head of the bolt that holds the pivot to the manifold. I neglected to take a picture at the time, but this photo shows the problem spot (along with my solution at the time, which was to cut down the bolt head for more clearance). (I've since reworked the pivot to have less slop.)
https://i258.photobucket.com/albums/hh260/TR3driver/TS13571L/th_DSCF0007-2.jpg (https://s258.photobucket.com/user/TR3driver/media/TS13571L/DSCF0007-2.jpg.html)

Yet another problem was caused (more or less) by replacing the nylon bushings that carry the linkage left to right. The new bushings were tight enough that they would bind when they got hot. (Probably doesn't help that my linkage shaft is not perfectly straight, so the bushings have to move a little bit as the shaft turns.) Fortunately, they seem to be wearing in enough that now I only get binding when underhood temperatures are very high. Should be OK with another few months of driving.

NutmegCT
06-25-2015, 08:17 AM
On my 59 TR, the linkage from the gas pedal as it passed through the firewall was binding on the firewall. Take foot off pedal, engine idled around 1500. Slight pull back on pedal, engine dropped to around 800.

Decided to live with it, as I didn't want to tear all that apart to replace the bushing. Toe exercise is good.

Lazy me.
Tom