Spark plug problem
Paul (Notts) - 5/1/08 at 04:23 PM
Spark plug problem
Having posted the SVA forms last week I thought I would do some work on the car today.
Job 1 – fit new coil
Job 2 – new dizzy cap
Then start doing all the small sva trim jobs.
Having fitted the new coil and cap ( 10 min job ) I then found I had a misfire. Replaced with old coil and cap and still had a misfire.
Cleaned plugs ( carbon fouling )
Altered mixture ( less rich )
Still misfire
4 hours later ( having used one of those flashy things on each plug ) I find two plugs are causing problems when they warm up.
Several burns on the hand later I find that when these two plugs warm up the central ceramic section becomes loose in the metal section and the plug
starts to misfire.
The question is WHY has this happened.
Rescued attachment nov06 182.jpg
MkIndy7 - 5/1/08 at 04:44 PM
Possibly the heat range is too low?
If there's various plugs for that engine and its state of tune, i.e the low compression engine might have different plugs to the high compression
or injection.
We had carb'd sierra plugs in our newly Injected/throttle bodied car and they mysteriousley broke.
They were heat range 6 and the injected ones were 7.
There's maybe more info in this thread I posted when ours were mysteriously breaking. http://www.locostbuilders.co.uk/viewthread.php?tid=76027
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I'm still not sure its cured as the Megasquirt hasn't really run properly since.
jollygreengiant - 5/1/08 at 04:54 PM
Could just be faulty plugs, it does happen. I had a customer complain about poor running on her car 30 miles after it was serviced. When I got to her
I found a plug lead barely/not connected (citreon/peugeot with the plug leads that seal into the plug opening). I apologised most profusely for the
error by the technician and she was on her way. The next day I got another call from her, about 25 miles after I saw her it developed another misfire,
so I went out to see her. Sure enough the same plug lead was off. I changed that one plug and never heard from her again.
On investigation when the plug got hot the gas sealant between the metal and ceramic failed until it got cold again.
Aidan_B - 5/1/08 at 05:25 PM
Bosch super 4s are complete crap, i serviced my 106 not long ago and put these in and the car misfired all the time until i put the old plugs back in.
People say you should never put them into a french car
rusty nuts - 5/1/08 at 05:45 PM
Have used NGK plugs for the last twenty odd years with very few problems.
Paul (Notts) - 5/1/08 at 06:02 PM
Oh well ...
another eight plugs then 
thats going to cost another £20+
Paul
Hellfire - 5/1/08 at 06:41 PM
As I work for a Spark Plug Manufacturing Company - all I can say is....
Are those Bosch Plugs and are you asking what's wrong with them?
If there are any more than three letters on them (Bosch = 5. Denso = 5) they're rubbish. Ask any biker or Racer and you'll get the only
answer you should have bought in the first place.
Steve
NGK
David Jenkins - 5/1/08 at 07:41 PM
NGK for me too - the only time the insulation has broken on them was due to my cack-handed handling.
MkIndy7 - 5/1/08 at 08:30 PM
Well mine were NGK's from 2 different stores/batches that messed up and there technical department had no real suggestion as to what caused
it.
If you did want another set of whatever brand there only about £1.50 each from Andrew Pages, as apposed to about £10 a set from Halfrauds etc.
