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Mark Tennison
New User
Username: fixstuff

Post Number: 9
Registered: 11-2020
Posted on Saturday, 19 December, 2020 - 03:23:   Edit PostDelete PostView Post/Check IP

So thanks to all for help so far, nearly out driving !

So fuel lines de-goo'd and renewed where required, primed fuel pump and turned the key, started and runs very quiet however, it has a misfired not really tried much so far as run out of time today but would like any suggestions for tomorrow.

Note: New spark plugs have been gapped(0.030) and installed, no change.

Many thanks
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Patrick Lockyer.
Grand Master
Username: pat_lockyer

Post Number: 2410
Registered: 09-2004
Posted on Saturday, 19 December, 2020 - 03:52:   Edit PostDelete PostView Post/Check IP

Is the miss fire the same hot and cold?
Could be the start of the opus electronic ignition failing.
On a simpler note it might be a HT lead!
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Mark Tennison
New User
Username: fixstuff

Post Number: 10
Registered: 11-2020
Posted on Saturday, 19 December, 2020 - 04:01:   Edit PostDelete PostView Post/Check IP

Patrick,

May be my imagination however, I feel that immediately after start it seems to run smooth without misfire but a second or 2 after start misfire is apparent and constant and I would say rhythmic not adhoc/random.

Cheers
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Robert J. Sprauer
Frequent User
Username: wraithman

Post Number: 664
Registered: 11-2017
Posted on Saturday, 19 December, 2020 - 07:51:   Edit PostDelete PostView Post/Check IP

Bring the car into a very dark location and look for subtle arcing from the leads to ground.
Although not precise, you may get lucky and see arcing. Old wires are a problem.
Another overlooked area is the dist cap and bad rotors that arc.
Check for vac leaks which are common.
Poor electrical connections are overlooked all the time and they are the non-obvious gremlins.
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Mark Tennison
New User
Username: fixstuff

Post Number: 11
Registered: 11-2020
Posted on Saturday, 19 December, 2020 - 08:20:   Edit PostDelete PostView Post/Check IP

Robert,

Thanks for the tips, will have a full day on it tomorrow.

All,
Was thinking of using the HT spark probe to earth/ground/-ve to identify if misfire is associated with specific cylinders. Any thoughts ?

Many thanks
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Graham Phillips
Frequent User
Username: playtime

Post Number: 339
Registered: 03-2019
Posted on Saturday, 19 December, 2020 - 08:57:   Edit PostDelete PostView Post/Check IP

G'day everyone,....

What Robert said,....

I would lean towards an ignition lead not snugly connected.

Just my thoughts,...



Graham.
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Mark Aldridge
Frequent User
Username: mark_aldridge

Post Number: 727
Registered: 10-2008
Posted on Saturday, 19 December, 2020 - 11:53:   Edit PostDelete PostView Post/Check IP

Mark, if you have a spare HT lead, try cylinder by cylinder substitution. I have had individual leads fail several times particularly in the metal sheaths. I no longer use the metal sheaths as on the post 1987 cars.
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Patrick Lockyer.
Grand Master
Username: pat_lockyer

Post Number: 2411
Registered: 09-2004
Posted on Saturday, 19 December, 2020 - 18:13:   Edit PostDelete PostView Post/Check IP

Or scope it for time saving if you can access one.

Or an ohms tester on each lead will confirm!
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Mark Tennison
New User
Username: fixstuff

Post Number: 12
Registered: 11-2020
Posted on Sunday, 20 December, 2020 - 18:56:   Edit PostDelete PostView Post/Check IP

By removal of each HT lead, I identified that 2 (1 on each bank) cylinders were not contributing as much as the other 6 however, by the time I'd finished trying different things and stop/starting the engine it gradually became smoother until by the end of the day it was running perfectly.! I guess the pre oiling of the cylinders as a precaution for the lay-up + a small amount of old fuel in the float chambers... may have contributed to the initial misfiring ? Was running that well we took it for its first short drive.
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Larry Kavanagh
Frequent User
Username: shadow_11

Post Number: 743
Registered: 05-2016
Posted on Monday, 21 December, 2020 - 04:59:   Edit PostDelete PostView Post/Check IP

Happy motoring, the more they're driven the better they tend to go.

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