Very Slight Misfire & Can't Pass Emissions

[madasafish]

Marigold gloves to insulate hands.

[Kremmen]

I think a good thick pair of gardening gloves, not sure if marigolds would do the trick ?

[Westy36]

E10 is due to be phased in from September the 1st. Pumps say E10 are actually E5 until then.

Good point. I'd just taken the label on the pump at face value tbh.

[culzean]

Marigold gloves to insulate hands.

My wife tells me the marigolds do not, under any circumstances leave the kitchen !

[MartinJG]

I use the black heavy duty ones for DIY 'things' so no problem there ....

[hp22]

So I tested the coils... unfortunately I do not think it's caused by dead coil...


For anyone that wants to test their coils.
1st. Grab a buddy that can help listen for the change in sound (in my case he was listening at the change of exhaust sound at back of the car as it was the best indicator)

start your car and let it idle
-Pull Both Power plugs for the coils for cylinder 1 , the car should start to run worse and exhaust puffing gets way way worse since it's only running on 3cylinders.Make sure to pull plugs for both coils,as the car can run kinda just fine on 1coil for the cylinder due to its design.
-plug in ONE plug for one coil and see if it gets better, if it gets better that coil is good..
-remove 1st plug so again running on 3cylinders, plug in the 2nd plug for the other coil for same cylinder, again if it gets much better that coil is working.
-Repeat for all cylinders till you hopefully find the faulty coil..

I didn't found any that was faulty
I wore thicker rubber gloves, however I don't think it's even necessary as it's all plastic in there...


So......what now?
Plugs have been changed, Coils tested, EGR cleaned, Fresh oil & all filters done, redex poured in and driven 150km, when plugged to computer shows no errors/faults.
Yet it still runs rough, kinda like misfiring..
 My local service probably doesn't want to see me anymore as well

[culzean]

No way in the world can you get a shock by removing a 12 volt plug encased in plastic with shrouded contacts.  I electrical regulations anything below 50 volts AC / 120v dc is considered 'extra low voltage' ( ELV )

[E27006]

I am assuming the valve clearances are all correct.
I would run a cylinder compression test to assess the state of the bores and the valve seating and sealing.
If the compression  readings are good,  then I would be looking for a failing fuel injector on one of the cylinders, the injector jamming shut or part -open. 

Question : does the exhaust gas smell of a rich mixture,  (excess fuel/petrol smell)?

[nowster]

No way in the world can you get a shock by removing a 12 volt plug encased in plastic with shrouded contacts.  I electrical regulations anything below 50 volts AC / 120v dc is considered 'extra low voltage' ( ELV )

It's the Volts that jolts, but the mills [milliamps] that kills.

If your skin is wet, even low voltage with sufficient current can cause problems.

[bobby boy]

Look for signs of failing manifold gaskets, PCV valve and it's pipework as well as small leaks from exhaust, anything liable to alter fuel mixture settings. Could be that catalytic converter is on it's way out also. As mentioned earlier compression test is well worth doing to prove main engine components are sound.

[Jocko]

Personally I would have done one coil at a time. If one is duff and one is good then removing both is bound to make it worse. Removing one at a time gives you a better chance of finding the one that makes no difference.

[culzean]

No way in the world can you get a shock by removing a 12 volt plug encased in plastic with shrouded contacts.  I electrical regulations anything below 50 volts AC / 120v dc is considered 'extra low voltage' ( ELV )

It's the Volts that jolts, but the mills [milliamps] that kills.

If your skin is wet, even low voltage with sufficient current can cause problems.

I clicked the wrong button and gave you a thank you I didn't mean to - not the first time I have done it

120 VDC / 50 VAC is considered extra low voltage in electrical regulations, which means if you touch it not enough current can flow through your body to harm you - 20mA is considered the safe limit of an electrical shock across the heart  - which is why earth leakage ( residual current ) trips are now 30mA ( shocking isn't it,  the current rating was raised because 20mA devices used to be too sensitive and prone to trip without reason ). 

So you should not unplug your 18 or 24 volt drill battery unless wearing thick rubber gloves and standing on a rubber matt, and never touch the terminals of a car battery when changing it.   

[E27006]

!2V is safe, but pulling the hot end of a coil may give you a stinging jolt as the spark tracks over the plastic casing and through your skin,  you may jump or spasm and bang your head on the bonnet edge, , get a sleeve cuff caught in something spinning (the alternator belt). You will get away with it hundreds of times then once you will be  bitten. You just do not know!

[sparky Paul]

What culzean is saying is that you can't get to the hot ends of the coils on the Jazz without removing them, and I doubt you would do that with the engine running! The only access is to the 12V connectors from the ECU.

On the old cars with a separate plug leads to a distributor, standard precaution was to pull the connectors with a pair of decent pliers.

[embee]

It's generally bad practice to run any HT system with no spark plug fitted and grounded so a spark can jump normally. Without this route the voltages can reach extremely high values, stressing the system insulation and usually resulting in tracking somewhere which is not good for the components. This is much more of an issue for older cars with distributors/HT leads etc.

Pulling a 12v feed off an on-plug coil won't do any harm to the ignition system though it will probably flag faults which will need to be reset and should not be done for more than a few seconds to avoid any possibility of overheating the catalysts (unburnt fuel/air will burn in the cat if it is hot enough to initiate it, they can melt down with too much heat, hence the misfire diagnostics etc).
OK to do these things if you appreciate the potential implications.