dj misfire pulling my hair out

[mark]

ive got a missfire 2.1 dj and this no doubt reads like the 100 posts on here and the 1000's of others ive read, it only happens now between 28 to 32 mph in 3rd
changed:-
plugs and leads
dist cap and rotor
temp sensor (which was a laugh )
afm (thanks aiden)
all vacuum pipes and checked the spiggots for blockages
air filter
disconnected the idle stabalisation unit and joined together
cleaned all the earths
cleaned all the electric connections inc ecu

it ticks over like a dream pulls like a train right through the rev range. just rubbish at driving round town in third

now the straw clutching begins
it has a bluetronic coil fitted part number xic 8051 0907 ive searched this but cant find it forsale anywhere(just different used ones on ebay)
anyone know if this is this the right coil for a dj or who sells them? its 18 months old knackered all ready?

ive read that the hall sender just goes without warning and that they play up before they go. who sells them? i couldnt find them on brickwerks,gfs and jk are out of stock


so far i havent changed anything that hasnt needed to be changed as per routine servicing apart from the afm and thats back in now

thanks for pointers or help
mark

[Ralf85]

Brickwerks do have the hall sensor. If you search on 'hall sensor' or 'distributor repair kit' you will see the options available.

Patrick

[Ralf85]

Also brickwerks point out that a faulty ignition amplifier can also cause problems.

Patrick

[Footprint]

it only happens now between 28 to 32 mph in 3rd

Are you sure it only happens in 3rd? If yes, then it would appear to be torque related, i.e. at those revs and that road speed when you want a fair bit of torque. Which would seem to point to your ignition suspicions being correct. Coil breaking down under load? Hall sensor can do funny things but running OK at all other times suggests it's not directly the culprit, but the wiring thereto may be suspect - perhaps check Hall wiring in the distributor for insulation problem.

Just a thought

[kevtherev]

Coil breaking down under load?

I know inside the coil are copper windings, and they are insulated from each other... if the insulation fails and the wires inside the coil touch the coil is useless.
The coil delivers a spark at whatever rate the hall sender requires, if the insulation in the coil around the winding has failed then it will just stop working I would have thought.
Do you mean if the insulation "breaks down" ?

but I don't understand what the "load" is

The coil can be detached and tested using a ohmmeter. The leads are placed on the outside prongs of the coil, and the resistance is tested. The coil should show a resistance somewhere between 0.75 and 0.85 ohms.

[mark]

The coil should show a resistance somewhere between 0.75 and 0.85 ohms.

thanks

perhaps check Hall wiring in the distributor for insulation problem

ill have a look at that thanks

Brickwerks do have the hall sensor. If you search on 'hall sensor' or 'distributor repair kit' you will see the options available. Patrick

cheers fellas mark

[mark]

hi all

checked the above all ok

checked the plugs not over fueling anymore temp sensor working

went for a spin still feel the misfire

rang a mobile tuner ive used in the past when i couldnt get a 009 to behave and explained what ive done and the syptoms

his reply was youve got an egg shaped tyre, if you havent ill check it for free

off to the tyre fitters and he was right offside rear like a bloody egg

thanks to everybody for their help

sometimes you cant see whats right in front of your nose

well i hope so going for quite a long run this weekend ill keep you posted

cheers mark

[Footprint]

offside rear like a bloody egg

Turns out not to be a misfire after all! Glad you've got it sorted.

So to expalin what I mean, (irrelevant now as not a misfire at all!):

but I don't understand what the "load" is

A misfire at high torque loads is sometimes due to an insulation failure in the coil, there is no short circuit as such*, but some cylinder conditions can find the point of least resistance in the HT system to be the insulation in the coil, (electrickery taking path of least resistance). High torque loads is a common time to find this** - at least early on in the insualtion failure, later on as the problem worsens the spread of the failure will broaden. Coil resistances take no account of fields and loads found while in use and as such are, at best, only a rule of thumb measurement, and aren't much use for coil diagnosis other than open circuit or dead short coil failure. A coil tester or occiloscope can help, (the ocilloscope trace is quite distinctive) - but if a fault other than open circuit or dead short coil failure is suspected it's usually easiest to check by substitution. Borrow one perhaps? You'll soon know one way or the other.



* An ignition coil - as I'm sure you're aware - is two coils on a common core allowing a voltage in one to induce a voltage in the other, as such it is a highly specialised example of a transformer, (specifically a pulse transformer), the two coils are insulated but failure is not always a dead short.
** Some Suzukis and Yamahas are known for this.

[kevtherev]

but I don't understand what the "load" is

A misfire at high torque loads is sometimes due to an insulation failure in the coil, there is no short circuit as such*, but some cylinder conditions can find the point of least resistance in the HT system to be the insulation in the coil, (electrickery taking path of least resistance). High torque loads is a common time to find this** - at least early on in the insualtion failure, later on as the problem worsens the spread of the failure will broaden. Coil resistances take no account of fields and loads found while in use and as such are, at best, only a rule of thumb measurement, and aren't much use for coil diagnosis other than open circuit or dead short coil failure. A coil tester or occiloscope can help, (the ocilloscope trace is quite distinctive) - but if a fault other than open circuit or dead short coil failure is suspected it's usually easiest to check by substitution. Borrow one perhaps? You'll soon know one way or the other..

Ah so you're saying the load is the load on the engine and this can induce a winding insulation breakdown within the coil?
I'd like you to expand that theory please...
So if it's not the insulation fault.. what other issues cause a coil to fail?

some cylinder conditions can find the point of least resistance in the HT system

eh? I thought the High Tension system started at the coil and ended at the plugs.
so how would something in the cylinder affect that?

[Footprint]

So you're saying the load on the engine can induce a winding insulation breakdown within the coil?

No, a partial breakdown in the coil insulation can show up under certain conditions. Ordinarliy high torques are the point at which this is found.

eh?

The spark gap is a resistance, yes? A very high resistance obviously, that resistance is bridged by sufficient voltage causing ionisation and a current path, a coil whose insulation is breaking down can sometimes have a resistance that is less than that of the plug, under certain cylinder conditions.

[kevtherev]

some cylinder conditions

why didn't you just say plug gap then?

I know I wrongly said the windings touch, metaphorically speaking when the insulation fails they do.
I understand that the energy will travel the least resistance... broken insulation will allow that

But I still don't see how an engine bogging up a hill will produce a coil induced misfire if the gap is correct.
poor timing will trigger the spark wrongly and cause a misfire under load.. I understand.

Surely the coil does not know the engine is under load, therefore will produce sparks whenever the hall sender tells it to

[Plasticman]

Pedantic or what
hey Ive driven it and it did not feel like a tyre/wheel problem , it was present in other gears to a certain extent, glad you sorted it
mike

[kevtherev]

[Footprint]

why didn't you just say plug gap then?

It's not about plug gap*, cylinder conditions, (specifically high volumetric efficiency - best cylinder filling, which is another way of saying most torque), effectively make the ionisation harder, in these circumstances a coil whose insulation is breaking down can be the point of least resistance and thus current flow.

But I still don't see how an engine bogging up a hill will produce a coil induced misfire if the gap is correct.
poor timing will trigger the spark wrongly and cause a misfire under load.. I understand.
Surely the coil does not know the engine is under load, therefore will produce sparks whenever the hall sender tells it to

If the ionisation requirements under all cylinder conditions were identical, it wouldn't matter, but they're not.

But a gap that's too large will make it worse, obviously.

[mark]

hi all
200+ miles and it did not miss a beat. did the slieghts hill in 3rd and hole of horecum in 2nd (up) pulling at all times

thanks everybody

mark