Subject: [TR] Causes of fast idle TR3

From: Frank Fisher <[email-masked]>
Date: Tue, 1 Jan 2013 17:42:37 -0800 (PST)

happy new year to all
B 
Since putting the TR3 back on the road I have
suffered an idle speed that I canbt get below around 1300/1400 at best.
Now
that the season is over I decided to fix some things.
When I put the car back
on the road I did not rebuild some parts under the premises of bif it aint
brokeb and i donbt spend cash I donbt have.
B 
B 
Had my distributor
rebuilt by Advanced. Fitted that today.
B 
Decided to work the carbs myself.
In the past when I sprayed a little starting fluid at the ends of the throttle
shafts it would bog down the motor..Just a little. It did NOT increase engine
speed.
I am running the TR4 PCV valve setup. The round pancake type. All new
diaphragm.
While checking the disassembled carb body I found the old throttle
shafts to be worn. About 0.010b undersize. But I found the existing bushings
to be only 0.002 max out of round and no worse than the new bushings I had to
replace them. So I did not replace the bushings. Max clearance now from new
throttle shaft to old bushings are from .002 to .0035. I have access to a very
big fully equipped machine shop with excellent facilities for measuring. Ibm
confident in those numbers.
Installed new butterfly valves with the Ground
surfaces to mate against carb.
B 
fitted the carbs today also.
B 
Got the car
together today and I have no improvement in reducing the idle speed.
B 
If I
put my foot under the gas pedal and pull it up, I can reduce idle speed by
about 300. it was always like that. adding a spring strong enought to do that
for me made the pedal horribly heavy.
B 
Disengaged the PCV valve to see if
there was an air leak. No.
B 
Squirted starter fluif around the intake
manifold. No change in idle speed.
B 
I guess I did not spray the throttle
shaft again! Duh! Will check that Saturday again.
B 
Car runs, but not right
just yet. I think I need to play with the timing some. No power at low revs,
kicks into power at about 2000. I think that I just need to mess with ignition
for now.
Exhaust note has changed though. Sounds like a tractor now and I
donbt have the 2500 howl.
B 
Any thoughts on where to start looking for
cause of idle speed will be appreciated and tried this coming Saturday
B 
Thanks
Frank

** [email-masked] **

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From: "Randall" <[email-masked]>
Date: Tue, 1 Jan 2013 18:41:34 -0800

> Any thoughts on where to start looking for cause of idle 
> speed will be appreciated and tried this coming Saturday

I assume you have already backed off the idle stop screws, and stuck a
feeler gauge in the gap to be sure the stop lever isn't hitting the stop.  I
once found a burr in there that may or may not have been causing trouble.

My next step would be to loosen the pinch bolt for the lever to the linkage
on the front shaft.  If the idle drops, you know the linkage is binding
somewhere.  Press down on the idle screws (which are still backed off so
they don't touch) just to be sure.  Might also be worth opening the throttle
quickly (just grab the fast idle lever) and letting it slam shut.

Block off the PCV again, and spray some starting fluid or WD40 around the
blockage and where the fitting joins the manifold.  As before, any change in
rpm (either up or down) indicates that you've found a leak.

Next step, loosen the linkage between the carbs, then listen at the intakes
to see which carb is passing more air.  Pull that carb off and start looking
for how air is getting past the throttle plate.  I don't mean to criticize,
but I'm guessing you'll find that either the plate isn't centered as well as
you thought; or got turned back to front somehow.

When my shafts were worn so badly that the engine wouldn't idle; I could get
the idle rpm down by blipping the throttle.  The wear in the shaft (and carb
bodies) was letting the front plate drag against the bore and bind if I
closed it by gradually letting off the throttle.  If that went on long
enough, I suppose it is possible that the bore would be worn into an oval
shape that the round throttle plate would no longer fit properly.

One last thought; on my last go-round I discovered that the idle stop lever
was installed too far away from the throttle plate, so there was a gap.
That allowed the shaft to move forward slightly when the throttle was open,
and then the plate would drag against the side of the bore as it closed.  It
eventually wore a step into the bore big enough to hang up on (even though
it was hard to see the step with the naked eye).  Inserting a shim next to
the lever, recentering the plate with the lever pushed up against the body,
and setting the return spring with the clip as close to the carb body as I
could get it (so it supplied some end force on the shaft) made a big
improvement.

> Had my distributor rebuilt by Advanced. Fitted that today.

Did you set the timing per his specifications?  From comments others have
made, I believe he uses a curve with less advance, so the initial timing
should be somewhere around 12 BTDC instead of the factory 4 BTDC.  Of
course, that will make it even harder to get the idle rpm down.

-- Randall