2 cylinder Suprex - warning sign?

[Thrumbleux]

Overtaking in 4th gear the power disappeared on selecting 5th - and it was obvious I was missing at least one cylinder. But, just prior to overtaking - at about 50-60mph in 6th - I could feel a slight vibration from behind. Made me think I should check engine mounts for any wear through the rubbers as it felt like metal on metal. A light but fast vibration - then the misfire and engine light. Has anyone experienced this or have any idea what it could have been?

No smoke from the exhaust and limped back home at reduced speed. Pulled the top plugs and #1 cylinder's plug is soaking with fuel, the other two bone dry and no sign of oil (though petrol could have washed #1 plug clean). Plenty spark on that cylinder and fuel, so suspect a burned valve but waiting for the correct size adaptor before I can compression test to confirm. No sign of damage to plug or bits of anything emanating from the cylinder head so I don't think catastrophic decapitation of the valve has occurred - but why the vibration?

[10:45PM]

Could it not have been the feel of the misfire, i.e. that cylinder lost when there's only three to start with, it's gonna have a noticable impact on smoothness apart from the obvious loss in output.

[Thrumbleux]

It was still running on three at that point. ******** in a Range Rover has a queue behind him at 30mph which took me down to 5th. Dropped into 4th to overtake (crawler lane) and at the top end of 4th it felt a bit flat then in 5th hardly any power at all. No vibes either - only when it was still running OK but a mere 30 seconds from calamity.

[tolsen]

No good for economy only running on three!

[10:45PM]

1d0jux.jpg


Maybe a coil pack , you might have a good spark at idle/turning it over , but at higher revs it might be giving up.

[Thrumbleux]

I kinda hoped it was just a failed coil pack hence checking it early but it's dishing out the brightest, fattest spark I've ever seen. HT failures always cause the engine to falter under load (increased cylinder pressure) but this miss fire is permanent. Compression test is going to reveal a burned valve I think. It's been using oil for a while now....

[10:45PM]

It's been using oil for a while now....

Now you say it.

I'll wait for the comp test results

[Thrumbleux]

Now you say it.

You only had to ask!

I'll wait for the comp test results

Next week - as I don't have the required adaptor as yet. I suspect we're sing from the same hymn sheet here. Still, 75000 miles on mineral oil before getting to this point aint bad. Shows just what BS is talked about fully synthetic oils.

[lalli_d1]

i personally dont think its anything to do with using synthetic oil or mineral oil, i think its down to the fact that a 6/700cc engine producing over 60 bhp which if you think about it its a lot of power for the engine size. i know bikes have smaller engines and produce much more power but bikes dont cover anywhere near the kind of mileage that cars will cover. over the same time period.

if synthetic oils were that bad then my uncles civic wouldnt have covered 200,000 trouble free miles... yes i know its japenese but even jap cars break down

[10:45PM]

A think this has its fair share of blame to do with it at some stage(s) of the cars life in a lot of cases........ At least a contributing factor tmp_24580-$_1.JPG-1120577216.jpg

[tolsen]

Post photos of all six plugs please and ensure they are numbered by cyliner and upper/ lower.

[lalli_d1]

good point. the engine is crammed in to a very tight space and it had limited space to keep cool, coolant can only do so much but space around the engine will help it circulate the air

[10:45PM]

Ahh soo you've sobered up again........ :-)

[10:45PM]

good point. the engine is crammed in to a very tight space and it had limited space to keep cool, coolant can only do so much but space around the engine will help it circulate the air

No I simply meant owners reluctance to go checking something that 'appears' to be so tucked away, not much extra work involved of course, but less accessible than just popping a conventional bonnet.

[137699]

i personally dont think its anything to do with using synthetic oil or mineral oil, i think its down to the fact that a 6/700cc engine producing over 60 bhp which if you think about it its a lot of power for the engine size. i know bikes have smaller engines and produce much more power but bikes dont cover anywhere near the kind of mileage that cars will cover. over the same time period.

If this is the case then can you please explain why the 700cc engine in the Roadster is proven to do 150,000-200,000+ miles without lunching it's piston rings or valves?