Expensive looking smoke from the exhaust.

[chrism964]

My 1990 c4 has started to produce blue-ish smoke from the exhaust at idle and under acceleration. From the smell of it it almost certainly oil that is being burned somewhere along the line. With the engine compartment open there is also a haze of blue smoke that drifts into the engine compartment from the vicinity of the exhaust secondary silencer area (i.e. drivers side of the engine compartment).
I cannot see any oil dripping onto the exhaust and the smoke stops when the engine is stopped (bummer).
The car has done 102,500 miles with full history but has not had any sort of engine rebuild (yet!)
There is no noticable fall off in performance or untoward noises.
The distributor belt appears to be intact.
I'm guessing that I'm looking at an engine rebuild (top or whatever) but I thought I would just ask to see if it could be anything less wallet damaging. I'm moving house in the next few months and so it would be good to know what I need to budget for.

So to recap the symptoms:

Blue smoke at idle when the engine is at running temperature.
A puff of smoke when the throttle is depressed that clears after 20 seconds (hot or cold) but returns at idle or if the throttle is lifted and then redepressed.
The exhaust fumes smell like burning oil.
The car doesn't appear to be using excessive amounts of oil. About 500mls in 3000 miles or so. However I have only noticed the smoke in the last 50 miles.
The oil level on the dipstick is between max and minimum.
There is no drop in performance.
There are no horrible noises from the engine (yet).
There are no warning lights illuminated on the dash.
My car has the M150 option and so has no Lambda sensor.

My wallet is now very scared []

 

[Guest]

If your not using that much oil it sounds like its more likly to be a drip onto something hot. I'm no expert so get it checked at a dealer on a ramp.

 

[Gordon Attar]

Have you had your car serviced recently? I had similar temporary problem when my car was slightly overfilled with oil.

I would also check the oil pipes in the rear o/side wheel arch area for leaks dripping on to the heatshields or exhaust, remember you need to keep the engine running as the oil all heads south(sump) when you turn it off.

Stage 3 see yoyur specialist.

If its possibly the topend, before going to this extreme get a compression test done first, before committing as you are not losing power or using much oil, Northway start at £2.3k plus the vat if that helps.

 

[chrism964]

Unfortunately I haven't recently had a service or added any oil. Everything checked with the engine at operating temperature with the engine running.
I can't see any drips but then again I haven't had it up on a ramp yet.
There is, however, a lot of oil vapour condensing at the exhaust tip.
Off to the specialist I think (hopefully it won't become terminal on the way).
I think it may be expensive. Just clutching at straws. (Oh and talking of clutches if the engine has to come out that could do with being replaced too..........)

 

[carreraboy]

Probably a bit of unburnt excess oil somewhere round maybe an oil pipe watch your oil pressure and level........don't worry about it it's a 911....

 

[Fred Hindle]

It could possibly be worn oil control rings allowing oil to stay in the cylinder when firing therefore being burnt. Hope it isn't though.
Cheers,

 

[Jeff Forsyth]

Chris,

Don't worry about the re-build as yet, over the years I've heard alot of scaremongering tactics from both members and Porsche specialists. As previously mentioned, the critical areas to watch are

(a) Oil Pressure
(b) Oil level
(c) Oil usage

Are you aware of how to measure the above ?

If in doubt, go to a specialist, and dont mention the dirty words 're-build'

Sincerely

Jeff

 

[chrism964]

Yes I have been keeping a close eye on all of the above (and measuring them all correctly). The car has used around 500mls of oil in 3200 miles. Oil pressures are good both cold and hot. Oil level measured when hot was half way between min and max.
However took the car to the specialist today. When I arrived there was no more smoke from the exhaust or smell. The specialist checked everything over (having the car for 3-4 hours and going on several test runs) and couldn't find anything wrong. I had previously taken the car out for several long runs to see if that would make any difference but it hadn't. So the verdict is that either something unpleasant from the road stuck itself to the exhaust and in burning off created the smoke and smell but then burned itself away or I was having some sort of hallucination or some miscreant had shoved something up the tail pipe that burned away.
The specialist didn't charge me a penny for their time as they said they hadn't had to do anything. I must say I'm fairly impressed with them and indeed the car is no longer smoking. Previously it was producing enough smoke (from the tail pipe and not from around the silencer) to fill my garage with a haze and a stench that lasted overnight!
The specialists were Strasse so a big thank you to them.

 

[Gordon Attar]

Chris

Good news

I should forget all about it(if possible)

ps the warning sign for rebuilds is usually around 500mls/1000 miles

 

[Jeff Forsyth]

Chris thats excellent news - they usually smoke at start up anyway- before I moved to Aberdeenshire, I lived in Yorkshire (Skelmanthorpe-Huddersfield) and Strasse did all my work and servicing. I'd reccomend them as I would Ninemeister.
Sincerely