TR2/3/3A TR3a correct engine idle speed

[Anthony_S]

Hello,

I was wondering if anyone could tell me the approx. correct engine idle speed for the tr3a after it has warmed up and ran a bit. I think mine is pretty high, about 2,000 rpm sitting at a stop light.

thanks
anthony

 

[NutmegCT]

Anthony - I think 2000 is a bit high for warm idle. Like about 1250 rpm too high.

Most folks would probably agree that 750rpm for a smooth warm idle is a good target.

There are *lots* of things that can cause the idle problem: mixture, throttle linkage sticking, vacuum leak, etc.

First thing I'd check is if the gas pedal is sticking. When the engine is idling fast with your foot off the pedal, try lifting up on the pedal (pulling it toward you). That'll show if the pedal linkage is binding, usually where it enters the firewall.

Tom

 

[sp53]

A nice clean low idle of perhaps 750 to 850 is the pinnacle of a well-tuned engine. The books say they could even be at 600, but fuel is different today. Again there are many variables and sequences to establish a nice low idle. First you need the proper engine mechanical components, good rings ,valves, tappets, ect then a proper functioning ignition system, then a proper functioning fuel deliver system ect . You get the idea. Anyways tr3s are very fussy idlers, but fun and easy to work on once you understand the basics. It will take some time, but it is not that hard. And yes the carb linkage is a good place to start.
Steve

 

[TR3driver]

I set mine a bit higher, around 1000-1200, simply because the idle speed varies so much with underhood temperature. Caught in traffic on a hot day, the carbs may be sucking 200F air, instead of 80F, which changes the mixture and idle rpm considerably. But I agree that 2000 is too high.

The place to start, of course, is by getting the engine thoroughly warmed up and then adjusting both mixture and idle rpm. The results of that exercise will help in knowing what to look for next.

My last high idle problem proved to be a combination of worn out throttle pivot (bellcrank under the front carb) and a sagged motor mount. The combination of the two was causing the linkage to drag on the manifold.

 

[sp53]

I respective disagree with Randall on this one. I would not start on the carbs until I have set the tappets cold at 10 thousand, the points at 15, new champion plugs @ 25, cap, and wires. I would then right before I tried to start it make sure the carb pistons fall smoothly. If they fall smooth and it starts, and the idle is not off the chart, I would check that the timing is not being pulled over by a shot vacuum advance. In short, I would not start messing with the carb settings just yet. In my view, they come later in the food chain. But having said all that, it would not surprise me that the high idle is a stuck piston in the carbs or perhaps low oil in the dash pots.
steve

 

[Anthony_S]

speaking of oil in the dash pots.....how full should they be? how can you tell?

 

[TR3driver]

But having said all that, it would not surprise me that the high idle is a stuck piston in the carbs or perhaps low oil in the dash pots.

I actually agree with everything Steve said about preliminary steps; I just assumed (and we all know what that does) all those steps had already been taken.

But low/no oil in the dashpots won't cause high idle; and a stuck piston will cause all sort of other symptoms (most likely without causing high idle).

 

[TR3driver]

speaking of oil in the dash pots.....how full should they be? how can you tell?

The minimum level is just enough so that you can feel some resistance when inserting the plunger. The earlier manuals suggested overfilling them slightly, which helps lubricate the sliding bearing, but confused owners because the level would not stay that high. The later manuals say the level is correct when you can feel resistance 1/4" before the plunger is all the way in.

 

[Darrell_Walker]

speaking of oil in the dash pots.....how full should they be? how can you tell?

Just full enough

If you start feeling resistance on the last 1/2" or so of putting the dampener rod in, that is probably full enough. Though I don't think overfilling and letting the excess drip out causes any problems (at least on an SU, Strombergs may be different).