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I have an intermittent misfire on my TR6. It is worst at revs below 2000 and when on light throttle. When you go to full throttle it pulls away fine once over @ 2000 rpm. My first though was ignition but i have a new electronic distributor, new plugs and new plug leads. Do injectors give the same symptoms as you would get with an ingition problem or do they go off and not work at all?

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PI can do that - the clue is the light throttle misfire. There may be an air bubble in a the fuel somewhere. Italian tune up would be my first action. Peter

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1 hour ago, Peter Cobbold said:

PI can do that - the clue is the light throttle misfire. There may be an air bubble in a the fuel somewhere. Italian tune up would be my first action. Peter

In other words give it a good thrashing.

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Phil

I would look first at the bits that you have recently changed before doing anything else.  Start with easiest to check first, leads/plugs and then electronic distributor.

Best of luck

Roger

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  • 5 months later...

I have been working on this problem now for a couple of weeks. Changed all the ignition system back to original, fit a new fuel pump, changed a couple of injectors and voila, I notice that there is no fuel coming to No2 injector at tick over and very little when reving. I tried injecting fuel back up the pipe but it did not cure it. The car had a reconditioned metering unit fit before I bought it a couple of years ago, its done less than 3000 miles since. It goes like a rocket once you get over 2250 rpm. Any ideas would be useful, how complicated is it fitting a replacement pump?

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Give it full throttle up a long hill to get #2 working properly, it may be air trapped and you need foot-to-floor, not mere rpm, to get fuel flowing as fast as possible to free off a stuck non-return valve in the MU.

Peter

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Thanks Peter it worked.

I took the car out last night to the nearest long drag. Flogged it up in top overdrive at full throttle and only changed down when the engine was labouring, it did'nt work first time so I did it again and it cured it. Now I can drive at 30mph without having to change down. I realise that is is very rare that I drive it at full throttle for any period. Only problem now is the overdrive stopped working.

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TR6's need to be run close to full throttle fairly often to prevent problems with the PI. I'm lucky to have a mountain range with good roads close to where I store the car.

Almost certainly the OD problem will be electrical- its so prevalent that I installed a green  "OD" light from a Landrover to confirm  that the  the OD solenoid is getting power from the OD switch.  

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2 hours ago, Phil Read said:

Thanks Peter it worked.

I took the car out last night to the nearest long drag. Flogged it up in top overdrive at full throttle and only changed down when the engine was labouring, it did'nt work first time so I did it again and it cured it. Now I can drive at 30mph without having to change down. I realise that is is very rare that I drive it at full throttle for any period. Only problem now is the overdrive stopped working.

Phil, Modern fuel is very different from when Lucas designed to PI...no lead, ethanol etc. When mine wasa daily driver the PI was exceptionally reliable over 150k miles. I suspect a combination of more aggressive fuel and long periods of lack of use cause many PI gremlins. Good that yours has an easy cure. Peter

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