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Triumph TR6 - Bad Misfire

Hi - I hope you can help.

A friend of mine (not good this web thing) has a very bad misfire on his TR6 PI (uk spec, runs unleaded plus Valvemaster Plus).

Symptoms are:

- engine fine up to 3.5k rpm
- speed up to 4K, and it misfires and returns to 3-3.5K missing badly

Happens under load (driven) as well as on the drive.

In all other respects the engine runs fine.

He's recently re-newed the injection pump (well a specialist said this was the problem and did the work to no avail).

It uses Luminition (optical).

Any ideas?

Thx vm


Sounds like ignition /timing..Check that the timing is correct try 8 -12 BTDC, also the plugs,cap rotor are good.
Charlie B.

I agree with Charlie. You might also check to see if the vaccum advance/retard (whatever a PI has I don't know) is working.

I've also seen that when the plug wires were old, cracked, and crossfiring.

good luck!
Tim Brand

May want to check for runout in your distributor's upper bushing. Take the cap off and see if the rotor moves side to side. There should be zero side movement. If there is and if you're running w/points you can guess what's happening to your dwell and burn duration of the affected plug(s). This usually happens around 2K distributor RPM (i.e., 4K engine).
Good Luck, Bob
Bob Sarama

Anthony I worked a lot on these cars back in the UK and what you describe assuming the ignition is correctly timed is a miss timed fuel meetering unit and although it may seem to run well at low engine revs when the air speed is relativly low, at higher revs the fuel is being injected not when it should be, maybe even on the exhaust stroke,I am sure you can find a site on the web that can walk you through the proccess and It is fairly easy, In a nutshell check out which injector hose goes to No 1 cyl and turn the motor over by hand until you get the timing mark lining up with the pointer make sure that the rotor arm in the distributor is pointing to no 1 cyl then remove inj.hose on the meetering unit and you should see the hole open. Hope this all made sense
Clive P

Thanks for comments.

BTW TR-6 PI does not use vacuum advance; I don't know why, since it aids economy.

Ignition is correctly timed. Rotor arms are always a weak point but this one looks good; will inspect more closely. Ignition system 'new'.

I'll check the fuel timing and report.


This thread was discussed between 16/05/2005 and 20/05/2005

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