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Smokey 924 2.0

im a bit green to these cars, but ive always been a VW freak from age 5 (courtesy of my dad) his dream was to own a porsche, 3 weeks ago i fulfilled that dream (with an albeit basic porsche!)

ive had a couple of problems but this one is worrying me the most....
i live about 2 miles from work but have to cross busy intersections to get there and back, the car is generally just warming up when i get there and when i get home, however, i was stuck in traffic today and the car got truly warm, the tick over started to race to appx 1500rpm and would not drop, it usually ticks over at appx 950rpm when cold,... i got home, popped the bonnet, and dropped it using the idle adjsutment on the throttle, got in the car blipped the throttle and to my horror i noticed a cloud of blue smoke throught the rear view mirror, took it for a race around the block, but all was fine,... no noticable smoke,... got back, let it idle for appx 1 min..revved to appx 4000rpm and again large cloud of blue smoke....

Anybody any ideas as to the cause/remedy - note it doesnt seem to do this when the engine is cold.

The car is 1984 924 lux 2.0 UK spec

h e l p.....pls

thanks

Mark
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1984 924 Lux (UK)
2.0 litre clean, original
Old 04-12-2005, 09:43 AM
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In summary:

When engine is warm and revved hard it plumes smoke (blue) oil is being burnt somewhere...

At idle no smoke is present.

any ideas anyone
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1984 924 Lux (UK)
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Old 04-12-2005, 12:04 PM
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It sounds like rings to me... not good news.
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Old 04-12-2005, 12:18 PM
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isnt the crankcase pressurised usually with piston ring wear? causing oil to leak into unwanted areas? (i might be talking rubbish but its something ive heard in the past) Could it be valve guide wear dyou think?

Mark
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1984 924 Lux (UK)
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Old 04-12-2005, 12:30 PM
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the engine has good oil pressure being around 5bar on start up at idle and ends up between 4 and 6 bar when driving normally when warm,...

I have heard also that the 924 2.0 doesnt use oil scraper rings?

any other things i should look for to diagnose piston ring wear for definite?
thanks

Mark
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1984 924 Lux (UK)
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Old 04-12-2005, 12:45 PM
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You need to do a compression and leak down test, Have the fuel mixture (CO, HC, O2, CO2) checked and make sure the breather system for the engine is not blocked. Adjustment without any reference to what is actually going on cures nothing. It maybe a minor problem, but without proper checking there's no way of knowing.

Yes, piston ring or excessive valve guide wear can cause smoking.
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Old 04-12-2005, 12:46 PM
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forgive me for being dim but how to i do the compression and leak down tests?

thanks

Mark
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1984 924 Lux (UK)
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Old 04-12-2005, 12:53 PM
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Go to a good, experienced and known Porsche shop, as to be honest, unless you can understand the readings there's no real point on doing it yourself.
Sometimes, you have to do the leakdown/compression tests cold and hot to just figure out what is going on inside and to get a reference.

You must have the Haynes 924 manual when working on this car.
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Old 04-12-2005, 01:36 PM
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is this an expensive operation usually?

thanks for your help by the way ,this is really appreciated

regards

mark
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1984 924 Lux (UK)
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Old 04-12-2005, 01:43 PM
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dont know whether this changes anybody's mind on the subject but it only seems to smoke after leaving to tick over for a minute or so,...second time i rev it it doesnt smoke as much third time hardly any at all....wierd, is that consistent with ring wear or valve guide?

thanks mark
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1984 924 Lux (UK)
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Old 04-12-2005, 01:59 PM
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what figures should i be looking for on a compression test?

thanks

Mark
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1984 924 Lux (UK)
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Old 04-12-2005, 03:17 PM
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I like to see around 150psi (or thereabouts, up to 175psi ). You are looking for all cylinders to be within 10% of each other. If one is real low, then there is a problem and more diagnosis is required.
Leakdown should be less than 10%, but cars will run ok with up to 20% without too many major problems. Again, accurate diagnosis and interpretation of the results is what is needed...otherwise no-one knows what the problem is or was or how much it is going to be to fix it.
Could be anything..have to have someone who knows about these cars to inspect and find the fault as just looking at it and guessing doesn't work.
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07.15.06 1996 Ducati 900SP. Suprisingly enough, it's red
08.16.09 1999 Kawasaki ZRX1100. Green.
Old 04-12-2005, 05:58 PM
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thanks for that im off to the porsche garage now......
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1984 924 Lux (UK)
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Old 04-12-2005, 11:26 PM
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