TR6 TR6 Timing issues

[TR3TR6]

I was reading the post about the TR3 timing and overheating iassue. My 76 TR6 seems to be lacking power and I had timed it using my timing light. I decided to use a vacumm gauge to check it out. It was only showing 13 inches at idle. When I advanced the distributor I could increse the vacumm clear up to 18 inches, but the idle also increased clear up to 2000 RPM's. Backing off the idle screws completely only drops the idle down to 1800 RPM's. It really has lots of pep now, but idles way to fast. The fast idle cams aren't engaged. With the distributor advanced I'm not getting any misfiring, in fact the car runs real good except for the fast idle. Anybody have any ideas on how to get the idle down?

 

[poolboy]

I doubt if it'll make much difference with the idle speed but try backing down to 17 and see what happens.

 

[TR3TR6]

I backed it down to 16 inches and it still idled at over 1500 RPM's. If I go back down to 13 inches, then I have to adjust the idle screws to keep it running but lost the power.

 

[poolboy]

Yeah well you don't want to do that.
The first things that come to mind are a hang up in the linkage or a vacuum leak, sucking in a lot of air.
Where did you hook up the Vacuum Gauge, the nipple for the Anti Run-on Valve on the manifold's banjo fitting ?

 

[TR3TR6]

Yes, I used the connection tp the anti-run on valve.

 

[poolboy]

It might be a good idea to eliminate the possibility of a linkage problem first.
On either side of the vertical control rod, there are those accordian like spring connectors that link the 2 carbs' throttle shafts together. Loosen a tiny nut on each of the connectors so that the accelerator pedal has no affect on the carbs. Each carb will operate on its own, independent of the linkage and independent of each other.
If the idle still hangs up, then it almost has to be sucking in air from somewhere other than the mouths of the carbs.

 

[TR3TR6]

I'll check the linkage first. If that's ok, then I must have a big vacumm leak. I replaced some of the vacumm lines because they had gotten hard. I guess I better check them all out. Thanks for the help.

 

[poolboy]

NP. I thought of a couple other possibilities. An air valve hanging up on it's own. Not likely but..
And, but I think you already checked this,. the fast idle cam is all the way down, right ?

 

[TR3TR6]

Yes, the fast idle cams are both down.

 

[TR3TR6]

I think what I'll try is disconnecting the vacumm lines one at a time and plugging them while the engine is running and see if I can find the leaking one.

 

[ekamm]

How did the water leak come out?

 

[poolboy]

I thought so.
So if it's not the linkage or an air valve, check every fitting on the intake manifold and the carbs. I guess you could include the manifolds themselves, too, for vacuum leaks.
Don't forget the nipple on the bottom of the front carb that goes to the dizzy.

 

[TR3TR6]

Eric

I haven't gotten around to testing it yet. I doubled the thickness of the seals around the door windows. I'm trying to fix some other issues besides the one I have posted right now. The 6 has started vapor-locking, so I going to reroute the fuel line from the fuel pump to the carbs. There's always something with these cars.

 

[TR3TR6]

I'll check everything, can't drive it the way it is now. Thanks.

 

[poolboy]

I think what I'll try is disconnecting the vacumm lines one at a time and plugging them while the engine is running and see if I can find the leaking one.

Good approach.
That vapor lock you mentioned; living down here in the Deep South, you can imagine the kind of heat I have to contend with. I did the rerouting of the fuel lines..no change.
The problem was that the exhaust manifold was boiling the fuel in the float chambers when the engine was turned off and no fresh "cooler" gas was moving into the float chambers. What was in there just sat in the chamber getting hot from the radiant heat from the manifold.
No problem when driving, just idling or during restarting, until enough fresh gas got in there and cooled things down.

Adding a heat shield helped but not much until I added a couple of layers of real insulation to the floor of the heat shield..
Now if you have stalling while under way, it's probably not due to heat, but rather lack of ventillation for the gas tank.
Flip the gas cap lid open and if the engine picks up again, that's what it was. The vent line from the tank to the Carbon Canister probably has overflowed gas in it's belly.
Just my experience.

 

[TR3TR6]

Mine is vapor locking while I drive. I didn't even think about the vent line from the gas tank. The first time it vapor locked I thought the fuel pump went belly up, but after it cooled down, it took right off and ran, so I new it wasn't a fuel pump issue. Something else to checkout. Thanks.

 

[poolboy]

If it does clear up when you open the cap then you will probably want to pull the end of that vent line off the Carbon Canister and blow compressed air into it..with the gas cap open. When you hear air enter the tank, the line has been cleared. Usually it's just gas from overfilling the tank and going around a curve that lets the gas make it's way into the vent hose and setttle in the belly of the line effectivly creating a vacuum in the gas tank as the gas level drops

 

[TR3TR6]

Update:

I replaced one of the vacuum lines, reset the idle screws and adjusted the distributor with a vacuum gauge. I was able to get the idle down to about 900 RPM's with 16-17 inches of vacuum until I stepped on the throttle and released; then the idle went up to 1300 RPM's and stayed there. Every time I stepped on the throttle and released, the idle would change either up or down. I checked the linkage and it seemed ok. The car has 53,000 miles on it. I'm thinking that the carbs are ready for a rebuild.

 

[poolboy]

400 rpm's . That's a bit high, but it's not inconceiveable that the Throttle Bypass Valve is staying open.
It's supposed to open when you decelerate or suddenly let up on the gas, then close when you return to idle or accelerate. When it opens, it lets some of the fuel air mix in the mixing chamber part of the carb Bypass the throttle disc and enter the intake manifold directly.
The TBV is surrounded by a flexible diaphram that responds to manifold vacuum to open the TBV.
The diaphram is prone to harden and loose flexibility and cause the TBV to stick. Maybe a replacement is in order. Moss #365-745 @ $12.95 ea. You'll need 2, one for each carb.

 

[TR3TR6]

When I remove the bypass valve diaphragm I will probably need new bypass valve gaskets??? Thanks.