24v missfire/inactive cyl

[richardbradford]

Update:

Definately an oil in the plug well issue. Cured the misfire by dropping in new plugs and replacing the cam cover and oil well seals - for about 5 miles, when stopped to find smoke pouring out from under the bonnet and an engine on 3-4 cylinders. Had been supplied with wrong cam cover gaskets which were leaking oil onto the exhaust manifold, hence the smoke, and preventing the spark plug well oil seals from sealing properly, hence oil dropping onto the plugs and a misfire.

Took the rear bank (the only one that had failed in the first place) apart again and found so much oil in one spark plug well that only the very top of the plug was visible. On the next one it was half visible and on the next it was mostly visible.

Now have the correct cam cover gaskets and cleaned up plugs and confident all will finally be well, on this front, after remaining reassembly tomorrow.

Richard :-)
164 24v Super 1995 - UK spec.

PS. Dumped my K&N for a standard filter at the same time - looses a bit of top end but prefer to have proper filtering instead of extra engine wear.

[MrT]

Gentle folk,

I submit that the oil bath issue can only suppress spark if the plug boot connector does not properly mate up with the plug top. For instance, if one leave off the screw-on adaptor for the top of the plug, the air space has not a prayer of holding off the spark, but if you then fill the plug well with oil, it will indeed insulate the plug from the wire and you may get no spark.

High voltage equipment commonly uses oil baths to insulate things within much tighter spaces than could be done in air. Any metal-to-metal contact will, however, conduct as well in oil as in air.

Michael

[alfapat@dsl.pip]

So changed oil and the new change is fast disappearing so still heavy on consumption, I don`t think its overspill but could be wrong as I wouldn`t get as much smoke as I do on hard acceleration, notice when changing downto turn into a junction then throttle again there is that puff of smoke again.
Going to try a stop smoke product as I think consumption is from a cyl letting oil past the rings especially #5 the one which has been washed by unburnt petrol, will see what happens but I take note of what you guys have said.

[richardbradford]

Quote:

Originally Posted by MrT Gentle folk, I submit that the oil bath issue can only suppress spark if the plug boot connector does not properly mate up with the plug top. For instance, if one leave off the screw-on adaptor for the top of the plug, the air space has not a prayer of holding off the spark, but if you then fill the plug well with oil, it will indeed insulate the plug from the wire and you may get no spark. High voltage equipment commonly uses oil baths to insulate things within much tighter spaces than could be done in air. Any metal-to-metal contact will, however, conduct as well in oil as in air. Michael

[MrT]

Research equipment for _serious_ high voltage commonly uses either compressed Sulfur Hexafluoride or oil. The oil has to be clean and not subject to sparking through it, because sparking through the oil leaves a nice trail of carbon which builds up and makes the oil conductive. A properly connected plug wire should not spark through the oil even if it is immersed. But in the case of loose connections, it could do that and build up enough carbon content to ground the plug wire to the plug well. I hadn't thought of that fault mode because I'm used to seeing clean oil in those appliactions. Nice, very clean, light amber oil that is replaced if it starts failing its voltage holdoff tests. So you're probably quite correct about the (dirty and carbon contaminated) plug well oil being the culprit.

Michael

[richardbradford]

Quote:

Originally Posted by MrT Research equipment for _serious_ high voltage commonly uses either compressed Sulfur Hexafluoride or oil. The oil has to be clean and not subject to sparking through it, because sparking through the oil leaves a nice trail of carbon which builds up and makes the oil conductive. A properly connected plug wire should not spark through the oil even if it is immersed. But in the case of loose connections, it could do that and build up enough carbon content to ground the plug wire to the plug well. I hadn't thought of that fault mode because I'm used to seeing clean oil in those appliactions. Nice, very clean, light amber oil that is replaced if it starts failing its voltage holdoff tests. So you're probably quite correct about the (dirty and carbon contaminated) plug well oil being the culprit. Michael