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Triumph TR6 - Missing under acceleration when engine is warm

My TR6 1971 missfires under accelaration after 15 or so miles when the engine temperature has reached its optimum. This is a regular occurence and I have changed the coil, points and battery all of which were old but not particularly well used. I was messing around with different fuels but now only put in high octaine with valvemaster additive. I don't want to change anything else until I can home in on the cause. As mentioned the engine is fine when cold but starts to splutter after 15 or so miles progressively getting worse. Any Ideas anyone. Thanks
Ian Gregson

Is your motor injected?
Don k.


I would check your fuel flow... it's possible you might have some blockage in you fuel filter, fuel pump screen, or more likely a malfucntioning needle valve.

I had a similar problem that turned out to the the needle valve was sticking. Using compressed air I was able to clean it out and now it's running wonderfuly!

good luck!

Adam Beasley

In replacing parts, did you replace the distributor cap? I had a similar problem a couple of years ago and when I looked closely inside the cap I could see where an incorrect timing setting had caused the rotor contact points to become worn causing the engine to stutter when the was a power demand.

Steve Paling

You didn't mention replacement of the plugs and/or wires. I have seen where a spark plug ceramic was cracked and when the engine is under a load the spark goes through the crack to the base of the plug, rather than across the electrodes, causing a misfire. When the engine load is lighter the spark will jump across the electrode as its supposed to. This type of problem can get worse as the engine heats up.

Good luck and let us know what you eventually find.

HP Henry Patterson

My money's on Henry!
I chased that gremlin once until one night, I saw an arc from a plug wire go into a heater hose. It would only happen when the car was warmed up.

Of course it could be in your carbs when you're not using the choke - unless your a PI kind-o-guy!

good luck!
Tim Brand

Thanks for those comments I will check them out. Yes the engine is PI but with a Bosch system. I'm afraid I know little more than that. I am off on businness to South Africa for two weeks but plan to hook the beast up to a crypton tuner when I get back just to see if that indicates anything. Thanks again will keep you all informed. Ian
Ian Gregson


My 76 had the exact same thing happen and I replaced EVERYTHING trying to chase the problem to no avail! What actually fixed it was closing the point gap smaller that what was specified (I don't remember the numbers) and bingo, it ran great! I don't know, but maybe the dizzy shaft was a touch worn, even though the side to side play was okay. Anyway, just something else you might try.
Chris Wiebe

This thread was discussed between 10/02/2005 and 17/02/2005

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