Oil separator valve? - Alfa Romeo Forum
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(Post Link) post #1 of 7 Old 19-03-11 Thread Starter
Status: R.I.P Allan Simonsen
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Oil separator valve?

1999 166 2.5 v6

been investigating my rough idle, and am starting to think its perhaps the oil separator valve..

when I changed the plugs a couple of weeks ago, i noticed there was quite a bit of oil inside the plenum chamber. upon starting it up and blipping the throttle this afternoon, i noticed just as the revs settled to idle, there was a puff of blue smoke. blipping the throttle again produced the same result, but smaller, and the third time revealed nothing.

given the smoke and the oil in the inlet, i'm starting to wonder if the oil separator valve has failed partially open. Could this cause a rough idle?

the car does quite a few short journeys, and is due an oil change. I didn't have any warning lights on, but after testing the MAf by disconnecting it, i do have the injection light on now (i was expecting this)

The car has only done 91,000 miles, so i seriously doubt any significant bore or valve wear, especially as it doesn't use that much oil.

any thoughts?

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(Post Link) post #2 of 7 Old 19-03-11 Thread Starter
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removing the oil filler cap with the engine running makes the idle a little slower, and worse.. coincidence?
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(Post Link) post #3 of 7 Old 20-03-11 Thread Starter
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right...

just tried a cold start, no smoke. revved engine, and again no smoke, so I can only guess it was a freak PCV problem. the engine on the cold start cycle dropped down to a smooth even 1000 rpm idle almost immediately, and the engine turns over evenly on the starter, so I don't believe its jumped a tooth on the cams, and also the belt is running true on the pulleys.

I tried diagnosing the idle issue bu unplugging various sensors, and got the following results.

lambda - no difference, plugged in or removed
MAF - no difference plugged in or removed - set injection light when unplugged
Coolant temp sensor. - difficult to start, idled about 300rpm for a moment, then died. no injector warning light.

I'm wondering if perhaps the CTS is starting to go out of range, perhaps causing a slightly over rich situation at idle (the idle miss / chug does sound like a rich mixture) though no black smoke, or fuel smell.

is it possible the rich idle has caused a little bore washing, hence the puff of smoke? its only done it once, with a smaller puff the second time, and never before or since..

As they are so cheap, i'm going to replace both of the PCV valves and oil separator can, just to eliminate them.

the other thing that nags me it may be a sensor going out of range is that the problem has gradually come on, and economy dropped off over time. i have kept the old plugs, they are a little dark, but they are all dry, deposit free, and all the same colour (more chocolate than rich tea colour)

Last edited by philoldsmobile; 20-03-11 at 13:15.
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(Post Link) post #4 of 7 Old 23-03-11 Thread Starter
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Bump... anyone??
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Silly question, but have you tried it on a diagnostic?It might show you if a sensor is going .. not all errors put the engine management light on.

PM me ... I might be able to arrange to meet up and hook you up to my AlfaDiag laptop depending where you are in Bucks ... south would be good! ;-)
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(Post Link) post #6 of 7 Old 24-03-11 Thread Starter
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dropping in to autolusso on sat for a scan.. thanks though
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(Post Link) post #7 of 7 Old 25-03-11 Thread Starter
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Found the smoke problem..

my driveway is on a bit of a slope, so topping up the oil isn't an exact science.. topped the oil up a while ago, and put about 1/2 litre in. now, probably 600 miles later, the oil level is still right on the max mark when I checked it on level ground.

i reckon I over filled it... hasn't smoked since!

should have an answer on the idle issue tomorrow as well, then MOT in a couple of weeks..
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