Classic Misfiring at 2-3000rpm

M

classic kev said:

The rotor arm and distributor cap - are they genuine Lucas or cheap pattern items? If pattern, change for proper Lucas.
The coil - is it a standard coil or a "high performance" coil ? The ignition system doesn't like performance coils.
Did you check your alternator output?

Good luck.

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Careful there are a lot of counterfeit Lucas parts about

If it's misfiring at that specific RPM, not above or below, could it possibly be an ignition timing issue? Have you renewed everything but the plugs? Could be they are not happy anymore...

I had a similar issue with a Gordini turbo, ran perfect if you pulled the lead off the top of the plug, that allowed the spark to jump to the plug, then at the plug itself again. Queer problem... But the Gordini liked platinum plugs!

fuel filter turned up today with parts for the Suffix A and the P38...

put the fuel filter on the 3.9.. checked the HT lead routing, checked the timing (several times) with the strobe.. still bloody misfiring. anyone fancy lending me a hand ?

Did you try a different fuel ecu?

If you've definitely ruled out all the electrical possibilities then next it has to be valves....

Measure twice, cut once. MAKE SURE the coils, leads & plugs are perfect, and if distributor, electronic or points are fine, check capacitor and anything else that may cause this electrically.

Failing that, I would be checking the camshaft, valves, exhaust manifold (for blockage) and any O2 sensors which may have have a bearing on the firing & burning of fuel.

no i did not pete. i could use the one from the CSK to test.

i dont think it's an ECU issue as it starts literally on the button and idles sweet and stable, when the RPM gets to 2000 it starts missing. i'll have to do a few bits on the P38 tomorrow then have more of a fiddle on the classic. I know i'm getting confirmation bias though!

any joy on the A post ?

doo.

you've given me a thought ! i wonder if one of the O2 sensors has taken a burp !

myfirstl322 said:

Inclement time of year, War Department 40 required.

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WD stands for Water Dispersal (or something similar) & the 40 is allegedly the number of attempts before the producer got the formulation right.

norseman said:

WD stands for Water Dispersal (or something similar) & the 40 is allegedly the number of attempts before the producer got the formulation right.

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Correct.

Think I'm free Friday 20th Adam if you can't get it sorted by then I'll swing by.

WhI have ecu does it have, I have known flapper units to give your problem.

norseman said:

WD stands for Water Dispersal (or something similar) & the 40 is allegedly the number of attempts before the producer got the formulation right.

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Damn you and wiki to hell...my granny says WD40's lubricity helped immensely on big ends during war time....

so.. as an update.. BTD very nicely paid me a visit and spent the day going through the possibilities with me.

its a lucas hotwire so dizzy with electronic ignition no dwell setting

1. disconnecting the O2 sensors made no difference whatsoever.
2. BTD and myself went through.. HT leads, Dizzy, Sandwiches, Tea, timing set to 6deg +/-1 deg, strong spark... pretty much most things.. we swapped the MAF from the CSK onto the Vogue and it ran a bit cleaner problem not solved.
3. pulling the plugs on right and left side (remember these have just been changed) showed them to be sooted up.

so, we seem to have it running rich on both banks, the only common denominator between both banks is the MAF. It starts, and idles sweetly its only when revved to 2000 rpm it misfires.

I ordered a pattern part MAF.. the only item available was ****part, it arrived today, plugged it in... it ran like a bag of nails it wouldn't even idle.. so one can only assume that the 'new' MAF is faulty as it wont idle with that MAF on. island 4x4 after a short phone conversation said that they wuld arrange collection and refund.

Still no closer to this getting back to running properly.

Sooty plugs point to rich running, very rich. is it getting enough air then? A mate once had a Vauxhall in that ran on idle, but man was it rich. Turns out, the air filter had got wet and been sucked into the manifold! Miracle it ran at all....

Have you checked the air intake system?

Zorst ok?
Seen a blocked zorst only a couple of times, so easy to discount.

myfirstl322 said:

Zorst ok?
Seen a blocked zorst only a couple of times, so easy to discount.

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Good call. That would also cause breathing difficulties

Think Pete was right iv now opted for coolant temp sensor or ecu earthlings and or dry joints, time for another road trip to Adams and pull the ecu out and have a look see

Did these cars have catalytic converters? Could the cat matrix have collapsed?

yes it has cats... new exhaust system and new cats and new O2 sensors less than 500 miles. (Dave was impressed that the oil on the dipstick is still golden)

all the temp sensors were replaced at that time too.