Mis fire

[alfadave]

I have a Plus 2 with Weber 40 DCOE/151's

Aldon 103 TC dissy.
Lumenition Optronic

Car broke down in July.......started misfiring after 20 miles, became worse and eventually stopped.

The Lucas DLB 105 coil felt very hot, so I replaced it with a Bosch 0221 119 027

I thought that had fixed it , but today, the same thing happened.

Car started from cold ok, ran for 10 miles, then misfired so badly I had to be recovered.

So, it seems to be a symptom of being fully warm.

NGK plugs, leads, cap, rotor are relatively new....but I'm not ruling anything out.

RAC guy checked I have a spark on all four.....but car won't run!

Any thoughts would be appreciated!

[Foxie]

Have you checked the points and condensor ?

[pharriso]

Aldon 103 TC dissy.
Lumenition Optronic

[mbell]

Do you have a old coil, cap, rotor arm, points condesor? Where did you get the replacement parts?

There a lot of poor quality new parts floating around that give similar issues. So test with old parts or buy parts from known good supplier (e.g. Distributor doctor.)

I'd also want to sanity check the carbs were getting fuel when the issue happened. Maybe pull out a jet and check the there is fuel in the well.

[webbslinger]

If it was mine I'd check the timing to see it hasn't "slipped", and at the same time confirm the spark and that the leads were tight.
If that checked out I'd look for fuel issues.

[Foxie]

Aldon 103 TC dissy.
Lumenition Optronic

Specsavers appointment arranged.

[alfadave]

RAC guy, with 30 yrs exp. is sure its ignition related.

Got Optronic, so no points or condensor.

Jon Bladen who repairs Lumenition items says if the optical switch or module fail then usually there is no spark.

Will check rotor arm and cap. Got them from SJ Sportscars.

Disributor Doctors description of how rotor arms can fail when warm hits the mark.

Will order a couple from him!

[alfadave]

..........RAC guy got a spark on all 4, after the car had been stopped for 2 hours.

[alfadave]

Havn't got an old dis cap here.

Where do I buy a quality one?

[Geoffers71]

This may or may not be relevant but I had a very similar problem on my V6 Scimitar. massive misfire which seemed to be random over any cylinder. I changed everything, one at a time; coil, HT leads, rotor arm, dissy cap, dissy itself, plugs were already new (NGK BP6ES, same as my Elan) Car was fine for a while then misfire returned. This repeated for weeks. I could never be sure of when the car would misbehave, so worried about using her. I decided to go for a rolling road tune and there were several issues identified. I won't go into details about what they were ( unless you really want to know !), but the main issue was ........PLUGS ! They were almost new, so they were dismissed as being the cause of my misfire. Big mistake. You can of course get faulty genuine plugs, but there are also fakes out there, convincing copies that are prevalent from dodgy suppliers on eBay and amazon, ( some genuine suppliers too on there of course, just need to be careful) I did some research to try any identify a fake plug and this is what I posted up on the Scimitar owners website
This is all available on the net after searching fake plugs. Many of you will probably know all about this anyway, but I couldn't find any discussion on the matter so here goes: it's common knowledge that fake NGK plugs are rife for sale on the 'net, but how do you identify them? First of all of course is to buy from a reputable source and avoid eBay and Amazon if you can. Not saying they're all necessarily fake, but you may be more likely to find them there.

These are the things to look for, ( not all may apply at the same time)
1. The gasket "washers" should be secure. They must not be able to be pulled down over the thread.
2. The 'P' in "MADE IN JAPAN" should be underlined. If it's not..fake.
3. The NGK printing should be properly central on the ceramic part, not too high or low
4. The colour of the metal part may be more gold than silver
5. The height of the central metal part, where the " made in Japan' is printed should be 8.48 mm. These fake ones are 8.23 mm
6. The printing on the ceramic part may be fainter and of thinner font
7. The electrode, the raised bent bit, should be a smooth curve, some fake ones are squarer closer to 90 deg bend.
8. Just above the hex shoulder on the metal part before the ceramic starts, fakes may show a sharper edge as if cut on a lathe rather than a curve

Fake is on the right
I hope that this will be useful. Take me to task if you disagree with any of my findings, but be kind.

[vxah]

Could you borrow an automotive oscilloscope to test things?
I had a similar issue and was able to easily test the optical pick up and the module output with the scope. It showed no dropouts from the pickup but I could see the missing triggers at the coil LT.
Module was sent back to supplier for testing (Aldon) and they replaced it under warranty!

[ericbushby]

Hi Dave.
When mine did that it was the rotor arm short circiuting to the shaft. It was OK at 1000 volts on the Megger, but with a lens I could see a tiny bubble in the black body.
It started fine to drive off the breakdown truck !!!
Eric in Burnley
S3SE DHC

[Sploder90]

Also check the cap clamps are securing the cap fully. Not easy to see on the car under the carbs.
Gives similar issues / symptoms to a worn dizzy spindle

Have had the white metal lugs let go before now

[Sploder90]

This may or may not be relevant but I had a very similar problem on my V6 Scimitar. massive misfire which seemed to be random over any cylinder. I changed everything, one at a time; coil, HT leads, rotor arm, dissy cap, dissy itself, plugs were already new (NGK BP6ES, same as my Elan) Car was fine for a while then misfire returned. This repeated for weeks. I could never be sure of when the car would misbehave, so worried about using her. I decided to go for a rolling road tune and there were several issues identified. I won't go into details about what they were ( unless you really want to know !), but the main issue was ........PLUGS ! They were almost new, so they were dismissed as being the cause of my misfire. Big mistake. You can of course get faulty genuine plugs, but there are also fakes out there, convincing copies that are prevalent from dodgy suppliers on eBay and amazon, ( some genuine suppliers too on there of course, just need to be careful) I did some research to try any identify a fake plug and this is what I posted up on the Scimitar owners website
This is all available on the net after searching fake plugs. Many of you will probably know all about this anyway, but I couldn't find any discussion on the matter so here goes: it's common knowledge that fake NGK plugs are rife for sale on the 'net, but how do you identify them? First of all of course is to buy from a reputable source and avoid eBay and Amazon if you can. Not saying they're all necessarily fake, but you may be more likely to find them there.

These are the things to look for, ( not all may apply at the same time)
1. The gasket "washers" should be secure. They must not be able to be pulled down over the thread.
2. The 'P' in "MADE IN JAPAN" should be underlined. If it's not..fake.
3. The NGK printing should be properly central on the ceramic part, not too high or low
4. The colour of the metal part may be more gold than silver
5. The height of the central metal part, where the " made in Japan' is printed should be 8.48 mm. These fake ones are 8.23 mm
6. The printing on the ceramic part may be fainter and of thinner font
7. The electrode, the raised bent bit, should be a smooth curve, some fake ones are squarer closer to 90 deg bend.
8. Just above the hex shoulder on the metal part before the ceramic starts, fakes may show a sharper edge as if cut on a lathe rather than a curve

IMG_1354.JPG

Fake is on the right
I hope that this will be useful. Take me to task if you disagree with any of my findings, but be kind.

Interesting.. thanks for sharing your findings.
Off to check my new & spare plugs now just in case

[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?