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Blue smoke / burning oil when warm idle and slow down

843 Views 5 Replies 2 Participants Last post by  rangerovering

I have a 93 Range Rover Classic with a 3.9 EFI which also runs on LPG.
Since a week I have the following issue:
Cold start, no problem, runs fine and I'm off to work.
When the engine is nice and warm still no problem until I get in traffic at the city and take my foot of the throttle and start slowing down...
Then after a few seconds I start oozing blue smoke (and when on petrol even some little back fires in the tailpipe, not on LPG).
When sitting idling at the stoplights the smoke keeps puffing gently.
When I pull away I leave the one behind me in a nice cloud of blue smoke, but as I rev up the smoking stops.
The engine runs fine on both petrol and LPG.

Any suggestions as where to look first?
I fear it is the valve seals or the piston rings, but would like some opinions / experiences before I take her back to the workshop and take the engine apart (since it's my daily driver ...)
Also read about idlve control valve could be an issue.

Any insights are highly appriciated.
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Little correction.
At cold start the engine starts smoking oil as well.
Just not in a big puffy cloud, but it graduatly builds up.
I guess that rules out oil dripping into the cylinder at rest.
Blue smoke on the over run I would start by looking at valve stem seals and valve guides. I would think your car has the old shower cap type valve stem seals which are not the best at keeping oil out the bores.
Thanks Rangerovering.
Do you know a way to test this or do I need to open the rocker covers to inspect?
I'll look for a replacement kit locally. Only the inlet valves have these, right?
Do you know if this is servicable without taking the head(s) of the engine?
Oil on a cold start is very likely because the oil has run down the valve stems overnight and is sitting in one or more cylinders.

You can take the rocker covers off and see what the valve stem seals are like (if they are still there!). They are on all valves inlet and exhaust.

If there doesn't look obvious damage to the seals themselves then the heads will need to come off and the valves removed to check the valve guides. If they need replaced (specialist shop job) then get them to fit the later type which have proper push on seals which fit to the top of the valve guide like a modern engine. They are much much better at doing the job than the shower cap type.
Just had a thought, do you have diagnositcs for 14CUX? With the backfires when warm it may also be running very rich and washing the oil off the cylinder walls and burning it down the exhaust. Check the coolant temp sensor is accurate and both lambda sensors if fitted are within range. Air flow meter also may be at fault
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