ok boys..... here's a good one.

I have an 89 with Lucas ignition. Starts up fine and settles to a smooth idle quickly. After fully warmed up I get an intermittent, irregular and unpredictable miss like a misfire/nofire at idle. Engagement of trans has no effect.

Coils: good long blue spark
plugs: new
wires: new
rotor: new
tps: old style, new
Reluctor and pick-up: good

heres the kicker.... it did the same thing only less so prior to the new parts. Doing some work on the dizzy currently as well and noted in my other post.

amplifier?????
ecu????

before I fall down that rabbit hole any other possibilities I may be missing?

help me cure my cat's little cough please.

Thanks.

 

I'm right there with you buddy. 86. Otherwise the same tale of woe. Just won't go away.

Plugs, rotor, cap, wires, amp module, clean all the connections. New pump, filter, sump screen, FPR, several injectors, all sensors, all vacuum lines, all fuel lines, set, reset, and re-re-reset TPS, clean throttles, perfect throttle gaps, throttle linkage perfect, no vac leaks anywhere; double and triple tested, new O2 sensors, clear flowing exhaust.

She misses.

Every major component replacement or significant fix and it's perfect for a bit. "That's it!" I think! Then she misses.

I think she likes me. I think she just wants me to pay attention to her. If she was running perfect I might spend a weekend with my girl. Un uh.

 

Worth a try when looking to cure an annoying occasional stumble is pulling the vacuum line to the L/H regulator.
The slight increase in pressure may fix a marginal injector or two and help to isolate the cause.
More often than not the stumble only ever occurs at idle.

 

For my part, not to snipe xjsfishs' thread, I tried that too. Nope. Stinky rich but still missing. And yes, it's only at idle. I'm thinking a couple injectors are just not up to snuff. Clean, but weak. But I've thought a lot of things that weren't. Upside is almost everything is new or refurbished now.

 

+1 on the notion that a flakey injector or two can cause a misfire-like idle roughness

Cheers
DD

 

+2 on the Injectors.

I ran Injector cleaner (snake oil) in my V12 cars regularly.

Removing the RH Fuel Pressure Damper/Regulator made the '85 much more like a V12.

AFTER I did ALL and more of what you both have done.

Adjusting the ECU Idle fuel "pot" made the balance 100%.

These might help.

Adjusting the ECU fuel pot.pdf

Jaguar V12 HE RH fuel reg removal.pdf

 

one of the plug wires was not fully seated.

 

Human error.

Very common.

Well done, NOW.