20 replies to this topic

[lxondecks]

Hi All,
Just noticed after a good drive that performance seemed to be down. Seemed to be misfiring and lacking in power.
Removed the plugs and all 4 are really black, wet and oily.
I had the plugs out the previous day and all were fine apart from one which seemed a bit dark but not wet.
Not sure what's happened, but it's all occurred after about 50 miles of driving and on all for cylinders.
Any ideas? Valve stem seals maybe?

Cheers
Lee

[cal844]

Is it oil or coolant?

[sledgehammer]

before you go any further - check choke returns fully

 

& breathers & pipes working ok

what is spec of engine ?

 

& as above - pics of plugs would be good

[kyle_1275]

As you said you’ve had them out recently so chances are the seals are the culprit. Just in case check that the carb needle is seated right and that the choke is not stuck on. Check the float level while you’re about it too oh and the obvious one, the filter. If all is ok then I’d assume the rings are on their way out. Is there any blueish smoke coming out while your driving around?

Edited by kyle_1275, 10 June 2018 - 07:17 PM.

[lxondecks]

It's a 1275gt. I will check the choke, but it was working fine before.
I had recently adjusted the tune as it was running rich. So had checked the float bowl, needle (sprung type) and jet settings. After tune the car was running fine.

Photos of before and after recent drive.  IMG_20180507_190004.jpg   34.01K   5 downloads  IMG_20180610_165908.jpg   28.31K   4 downloads

I wouldn't say it's smoking excessively. had someone following me and they said there was no smoking.

Just seems strange how the performance dropped pretty suddenly now all plugs are in this condition.

[kyle_1275]

If the performance has dropped dramatically but there’s no smoke while driving then it could just be the valve seals, explains the amount of oil on your plugs too. Too much oil making its way in to create enough of a sufficient spark.

[lxondecks]

Thanks for your reply.
Does it seem normal for all seals to go at the same time?
I'll try replacing these as its a cheap fix and hopefully it resolves the issue.

[sledgehammer]

is it definitely oil ?

 

surly that much oil would cause smoke ?

 

I would clean the plugs -- take it for another run before stripping

Edited by sledgehammer, 10 June 2018 - 09:21 PM.

[kyle_1275]

As sledgehammer said, give them a clean up first and a decent run out and see if you get the same result.

It’s not unusual for them to go at the same time especially as you said yourself you were running a little too rich before hand. Running richer means running hotter so I wouldn’t be surprised if this was the case. Start with the cheapest fix and work your way up while praying it’s not something major. Good luck and keep us updated!

Edited by kyle_1275, 10 June 2018 - 09:27 PM.

[lxondecks]

It smokes a little when called but then cleans up. It definitely looks and feels like oil. I've got a spare set of plugs, so will install those and take for another run and see how they look.

[kyle_1275]

Definitely sounds like the valve stem seals to me with how you describe it. It could potentially be the valve guides themselves but I’d still put my money on the seals being shot as it’s quite a bit of oil on the plugs.

[Rorf]

You don't give us much history - how long has it been running before this problem ie how many miles over what time period. What carb does it have, HS4 or what.

 

You played around with carb settings now you have a problem - looks like over fueling to me, fuel level is too high. Unusual to have all four plugs oiling up unless the engine is knackered.

 

Those plugs are wet with fuel/petrol.

[lxondecks]

Hi,



It’s a 1275GT with HS4 carb.

I’ve had the car running for about 2 years and done 2K miles over that period.

up until the last trip I’ve had no black or wet on the spark plugs except cylinder 4 which has always been a little darker (but not wet).

The head gasket was replaced a couple of months back as it had blown between 2&3 cylinders.

After head gasket was changed I adjusted the carb settings as it was running a bit on the rich side. I leaned the carb by 2 flats on the adjuster nut.

Car was running much nicer. Plugs had cleaned up nicely and much better performance.



Then I had a leak from the radiator whilst on motorway and lost about half my coolant before I spotted it and topped back up.

Once I got back checked my plugs, colour looked okay, no black or wetness. I completed a compression test to ensure head gasket hadn’t blown.

Car seemed to be running okay.



Then the next trip was 50 miles, mainly motorway. Performance seemed okay on motorway, but idling and around town driving it seemed to be misfiring and sluggish.

Checked my plugs again to find what I’ve said above.



How are you sure that its fuel and not oil?

[sledgehammer]

Quote -

How are you sure that its fuel and not oil?

 

 

 

 

IMHO if it was oil , it would be smoking quite bad , a rich mix will wash some oil off cylinder wall , giving an oily wet appearance , 

 

also usually valve stem seals will leak worst when the car is in over-run , when inlet manifold vacuum is high , it sucks the oil thru the valve stems

 

does it smoke when in over-run ?

 

 

[MatthewsDad]

Having been through the same issue with a twin carb set up recently I'd agree with sledgehammer. I actually had both stem seal problems and too rich a mix, but once I'd sorted the carbs (and ignition) I no longer had wet plugs, though I still have smoke as I haven't bothered with the stem seals yet.

Although not especially scientific does the exhaust smell of unburnt fuel or burnt oil? Burnt oil is acrid and pretty unpleasant. You may only be pushing out the smoke under certain driving conditions as sledgehammer suggests, so might be worth another road test with a friend driving behind you and the windows down. Just a thought.