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TR6 TR6 Idling Problems

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jerrybny

jerrybny

Jedi Knight
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Happy Friday all. It was a beautiful day in NY. Went for a nice relaxing ride. Anyways on to my problem. After warming up the engine I set the idle to 850 rpms. However after awhile the engine increases its rpms up to about 1100. It stays there for awhile and then eventually drops back down to 850 or so. It keeps repeating this pattern. Any suggestions on where to start troubleshooting? I done the normal stuff like checking the vacuum hoses for leaks, etc. Thanks in advance for any advice. BTW its a 73 TR6.
 
Is this all happening during the steady idle where nothing is being touched and the choke is off? Are both chokes shutting off totally? Once the knob is pushed home, can you push either choke any further by hand at each carb?
Is the engine running smoothly throughout this entire cycle?

Something that helped my idle and the total performance of the engine tremendously, was to completely disassemble the distributor and thoroughly clean it with carb cleaner and relubricate it.
 
If this is happening during prolonged periods of idling, heavy city driving and/or from high ambient temperatures. This could also be the thermostatic valve working if its all still in place.

If the valve is working correctly, it would shut off the vacuum to the retard side of the distributor when the coolant temp got too high, advancing the timing and allowing the engine speed to rise, which in turn means greater coolant circulation. Once the coolant temp dropped enough the valve would re-open, retard the timing again and lower the idle.
 
Yes it happens during prolonged periods of idling. It doesn't do it when the car is first started. It takes a while before it happens. So it is possible you have diagnosed the problem. I will keep an eye on it and see. I believe it is happening whenever my electric fan kicks on which is around 185 degrees.

Thanks
 
Then I would thinkif your thermostatic valve is still set up as the factory had it, then you most likely have nothing to worry about.

But way to pay attention to even the smallest things your TR does. Thats the way to really stay "in tune" with the car. :thumbsup:
 
That was a good idea from swift6. You can test that out by removing the vacuum line and fitting to the retard unit on the Dizzy next time this occurs. If you feel no vacuum on the line with your finger tip and if the engine doesn't speed up more then he nailed it.
If the Thermostatic Vacuum Valve is not the culprit, it might be the Throttle Bypass Valve failing to close. But that usually only occurs coming down from speed to idle, not from normal idle speed back up to a higher speed, as I understand your description.
 
This might sound totally stupid but my car does
that sometimes. 800 to 1100 rpm. When it happens:

I spray the carb coupling with thin oil and the idle
slides back to 800.

d
 
I pulled the vacuum line to the dizzy when the rpms increased and there was suction on the line. This would lead one to believe that its not the thermostatic Vacuum Unit that is causing the increase in the rpms. <span style="font-weight: bold">Right.</span> Also another thing is that when the idle comes back down a lot of times it drops to like 600 rpm and the engine wants to stall. Any other ideas, things I should check out. HELP :cryin: I'm gonna call it a nite and maybe tomorrow there will be some fresh ideas. Thanks all for the help
 
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