Mis fire

[alfadave]

My NGK BP 6 ES plugs tick all the genuine boxes fortunately.

Dissy was rebuilt by Aldon, and clips hold the cap ok.

Dug out an old Lucas 45D rotor arm....will try it tomorrow......on a circular route near home!

[Geoffers71]

[quote="lotusfan"]Geoffers 71

Thanks for publishing that very useful information on fake NGK plugs. I have just fitted a new set of NGK plugs, purchased from a reputable source, to an E-type Jaguar and it is exhibiting the rough running symptoms described. I will investigate the differences between the old and new plugs but first difference is that every NGK plug I have ever bought says 'made in France', I have never seen a Japanese one.

What are other peoples experiences Japanese vs French NGK plugs?[/quote

NGK plugs are made in a few countries including Japan (obviously), France and the USA. Depends on your supplier which ones you get I suppose. I have French ones in blue too although they’re
BPR6ES , resistive type. Dunno if all French plugs are in blue, but I suppose they are more likely to be genuine as why fake them?

[alfadave]

I realised that Moss Europe, near me keep Distributor Doctor rotor arms in stock.
So, I picked up two of their GRA 2114 HQ arms this morning. Stamped DD.Suitable for 45D type dissy.

Did an 18 mile slow, stop start run near me.... seemed ok at first....

Then I heard a loud spit, then the car started mis firing, and I struggled home for the last mile.

The car will start, but no power, and won't tick over.

Any more thoughts?

Replacement cap is in the post.

[Sploder90]

Initial breakdown at 20 miles, latest issue at 18: I wonder is it heat related?

Leads breaking down and shorting when warm... do the leads cross each other and have a similar effect.
Check dizzy cap carefully for cracks and also that the screws for the leads are secure but are not right through the cap itself..I

Odd concept: Electric fan?.. How is it wired could it be shorting / robbing coil voltage?

Ballast resistor if fitted

Have heard of but not personally experienced radio suppressor breaking down and affecting coil.

or is the wiring loom old / brittle and shorting somewhere when warned up.

Try taking a direct live feed to the coil and to the dizzy with new cabling and do the same test drive route.

Is it definitely electrical?
Carbs / compression / valve clearances. Again heat may be the cause but not the culprit as things expand and move.

Air leak to vac pods?

On mine there was a slight split in one of the vac pipes just where it goes through the bulkhead and things changed when it moved and when they got more pliable.. Had issues with the lights but I don't use the manifold vacuum anymore so it didn't alter the fuelling but it potentially could..
Have a look at No 1 plug does it look lean?

Good luck and let us know when you solve the problem.

[alfadave]

I must admit there was quite a strong fuel smell before the car started mis firing today......

but not the other two times it broke down.

Maybe needle valve?

I do have an in line fuel filter, and of course one in each Weber

[Geoffers71]

Your symptoms are exactly the same as I had with my Scimitar. Spitting back is caused by initially unburnt fuel igniting in the exhaust. This MAY be timing ,but I doubt it as it runs fine for a while. So a plug or plugs is/are not firing. (So you can smell fuel?). This could be anything on the HT side of things. I'd be tempted to go back to points and condenser and see if that makes a difference and buy another set of genuine plugs. (Even genuine ones can be faulty, some "experts" don't advocate trying to clean plugs as it doesn't guarantee they will still work). Also a rolling road tune can reveal wonders, (I can vouch for that)
Hope you sort it soon.

[Sploder90]

Check float heights and that there isn't a hole in one, but can't see why this would suddenly manifest itself after a few miles unless something to do with the test route..

Tight uphill right handers and pulling out of uphill junctions has been mentioned previously as causing problems in here. Think this was float height related and could be cause of fuel smell. But wouldn't explain why still misfiring afterwards unless it fouled the plug sufficiently.
But...
Lean webers can also spit back out of the carbs and leave un-burnt fuel in the airbox..I

once had a progression cover come loose and fall out on a 1700 x flow with webers ..that caused weird running until we spotted it.

[Andy8421]

Any more thoughts?

Replacement cap is in the post.

I have had exactly your symptoms with a dud distributor cap, purchased from Aldon (many years ago). When hot, the cap's insulation would break down internally, and the car would splutter to a halt. Leave it to cool, and all was OK again. I tested it in the oven with a multimeter, and the resistance reduced rapidly as temperature increased. I bought caps from other suppliers, and they exhibited the same effect to a greater or lesser degree. This is ancient history now, but there was clearly a bad batch of caps in circulation about 10 years ago. All the usual suspects had them.

The tell tale was the square moulding sprue on the top of the cap. Good caps didn't have this, every bad cap i found had the same mark. If your cap has this sprue, I would consider this a very likely culprit.

Thread here has a picture of a cap with the mark.

https://lotuselan.net/forums/viewtopic.php?f=38&t=47440

Good luck. These sorts of failures are a pain to track down.

[alfadave]

Thanks Chaps......

A few answers:-

Leads in VGC....plugs NGK BP6ES, 2-3 yrs old, and not mega mileage....but have wire brushed them a few times.

No ballast res
No radio/suppressor
New loom 5 yrs ago
Comp test all 200 plus
Pods run via MX5 motors.
Dis cap is push in type, not screw in. GDC 142. Just picked a new one up from Moss Europe.Seems the Mini had the same.

No points/condensor. Lumenition Optronic fitted.

RAC guy put a test light on all 4 lead to plug connections. All 4 showed ok, but of course this doesn't mean the plugs are ok.

Has been on rolling road twice in last few years.
Timing set with strobe recently.

I've got a box of new genuine NGK plugs here. They come in boxes of 10 for some odd reason.

Will fit them in the morning, and do 20 miles locally.

A guy at the local tyre place waved to me several times today as I kept passing!

[Sploder90]

I have had Lumenition modules pack up in the past on other cars & / or the thin feed wires between the module and dizzy the insulation splitting exposing the core.

I ditched mine in favour of an Aldon ignitor on recommendation from both Chris Foulds & Paul Matty when I got the distributor rebuilt.

Lumi Parts went to another member on here as spares for his car.

[2cams70]

Get another distributor with points and condenser! Doesn't have to be from a Lotus. Can be a cheap one from anything with a Kent series engine - Escort, Cortina etc just to get the engine running. Substitute it and see if the problem goes away. If it does you know what your problem (My guess is the electronic ignition. Most of the aftermarket ones are cheap rubbish). Once fixed you can then keep the other distributor as an emergency get yourself home one.

[alfadave]

Fitted new NGK 6's.
Only took 9 miles for the mis fire to appear!

So far I have replaced coil, rotor arm, and plugs.

Cap is next.....followed by leads.

I've got a spare Lumenition module, so will try that.

Away for a few days, so will restart next week.

I am aware that I am replacing parts based on hunches/peoples advice, without a proper diagnosis.

Unfortunately, my long standing mobile auto elec fell victim to the virus earlier in the year. I do miss his knowledgeable and experienced input.I suspect he would have diagnosed it by now.

[Slowtus]

Late to the party here - leads - (and I'm not just saying that because everything else has pretty much been eliminated and others have said the same ). Had similar many moons ago and while the leads tested fine, they broke down in similar fashion.

[alfadave]

Got a set of Burton BPL09 BK leads, and fitted them today.

Same flat test run......mis fire started after 11 miles......just struggled home.

Cap is next. Can't see anything obvious with the current one though.

I've got a new aftermarket one here, but found an original Lucas one on Ebay, which is on its way.

[alan.barker]

Bypass Ignition Switch and feed Ignition direct from battery. See what happens and if ok then the Ignition Switch needs replacing.
Please try you have nothing to loose.
Alan