odd smoking problem

[88911inga]

Hey guys, newbie here. I recently acquired an 88 Carrera w/ 80K on the clock and have been grinning ear to ear ever since. I've driven several over the years but always found something that scared me away. Not with this one. Anyway..
I have recently noticed severe smoking while idling for a while. Under acceleration/deceleration friends have noticed none. After warming up, it goes away. The plugs are all a nice tan color, so I don't believe it's in the chamber.
I read a few posts here that suggested the oil was overfilled and I just need to clean my air box; not my case, box was bone dry. I did a valve adjustment recently and it seems to have gotten worse!! Any ideas here? Anyone have a good way to troubleshoot this?
Thanks in advance,

Brad

[atlporsche]

first off, where is your oil level?

don't forget you check it with the car at temp and running.

sjd

[88911inga]

Oil is 3/4 full @ mid scale on temp.
Thanks, Brad

[axl911]

Valve guides!!! Same thing happenned on my C2. Rebuild confirmed the valve guides. Start keeping track of your oil consumption. Mine went from 1000 to 400 miles/quart before I did a top end.

[axl911]

Somehow I missed the part about "going away" when warm. In mine, it would smoke when hot.

[MBEngineering]

HI how tight did you adjust the valves?? at 80k the stem seals will be hard and untill the engine warms up thay will let the oil past on the valve stem.

regards mike

[88911inga]

axl, I used the tool from Pelican and tightened them down to the point where the guage slid out freely with mild resistence. I did run into something strange while doing the adj; the tdc mark was lined up perfectly with the center of the case but the rotor button was just ahead of the distributor mark.....?

MB, I thought about seals, too, but my plugs are showing a good clean burn. No blackness at all. I just went out and re-verified this as to not be a liar. Wouldn't they be showing some signs of worn seals? My oil consumption is kind of high around 650 or so per qt. I do use my car as a daily driver and mostly in the city. I've read this doesn't help consumption at all??

Keep 'em coming guys, this is really embarrassing

[MBEngineering]

HI if the exhaust guides/valves/stem seals are worn it will not show up on the plugs,

regards mike

[MattAlpha]

When your car is warming up, what is it idling at?
From my understanding, it should idle at 800 rpm.

Mine 911 smokes during warm up only and is idling at about 650 rpm. From reading a few other posts here, it seems to be a control sensor problem that causes the engine to run rich and idle low. When the circuit is jumpered the idle goes to 800 rpm and the engine gets the appropriate amount of fuel and it doesn't smoking while it warms up.

If this sounds familiar to someone else could you please expand upon it.

[88911inga]

MB, yeah, that's kinda what I was thinking, too. It seems like oil is dripping into the exhaust manifold, being burned off, then all is well. I was hoping that someone had this exact problem and could say for sure that it was guides/seals. That way I am not just throwing parts at the problem. Could this just be the seals and not the guides with only 80K on the engine? All the maintenance records show regular changes and a valve adjustment @ the 60K inspection.
Matt, the idle is perfect and right on 800 RPM, so the sensor idea doesn't sound like my problem. Good luck on yours though. I am new to these cars and wish I had some experience to help you.
Thanks much for the replies guys, Brad

[MBEngineering]

HI as a check, pull the lower rocker covers off and as if to set the valve clearances, turn the engine to No1 and check the movement (sideways)on the top of the valve/spring retainer on the exhaust, for a guide as to the wear in the stem, with a screw driver gently push the top over to check, do not go mad and bend the valves then turn over to 6 and so on. if you feel movement poss the guides are worn, sorry but you will require a top end job on the engine.

regards mike

[Early_S_Man]

Brad,

3/4 way up on the dipstick is a bit high for the oil level ... 1/4 - 1/2 up on dipstick is optimal. Remember -- there is a two qt. range between upper and lower marks on the dipstick ... and even at the low mark there is over 9 qts of oil in the system, i.e., it isn't at a danger/low level!

My suggestion is to run the oil level at the 1/4 - 1/3 way up between the marks on the dipstick for a while and see if your consumption 'problem' goes away??? By 1988 the factory had presumeably solved the problem with premature valve guide wear due to the orange elastomer valve stem seals, and 80K would be too soon to be showing valve guide problems. Your worries may be needless!

ps,

If the smoking is only at startup, and completely disappears after a few minutes of warming up, then it really isn't a problem at all!
Do a search on the string 'smoke at startup' and you will find many, many threads on the subject ...

http://forums.pelicanparts.com/search.php?action=showresults&searchid=2024783&sortby=lastpost&sortorder=descending

[Steve87-911]

Mine was smoking when it idled too long at a smog check station. I found that the O2 sensor was disconnected. After reconnecting it the smoking stopped.
Even though yours stops smoking after it warms up, it still can't hurt to check that the O2 sensor isn't unplugged.

[88911inga]

Thanks guys all good suggestions. I'd never heard about running @ 1/2, but I'll give it a shot. I was afraid of starving the engine. Can I just replace the seals without a full top end job or am I doomed?

Looking over my posts I left out a very important detail. Immediately upon startup I get the obligatory puff then nothing. After idling for about 2-3 minutes the smoke starts and goes on heavily for another few minutes then goes away. That is what makes this odd.
I really appreciate you guys helping me out. I was a BMW guy until this and so far both communites of owners have been nothing but great. Thanks again and don't give up on me yet.

[ianc]

HI if the exhaust guides/valves/stem seals are worn it will not show up on the plugs,

I'm curious as to why you would say that. Oil getting into the combustion chamber, no matter how it gets there, is going to get burned, and that will cause deposits on the plugs. Or so my thinking goes anyway...

ianc

[Early_S_Man]

ianc,

When the oil seeps past the exhaust valve guides with the engine at rest ... it never goes into the combustion chamber! It drips off the valve stem down to the exhaust port, into the heat exhangers, and ultimately into the catalytic converter -- provided the sit between running is long enough, into the muffler to pool and collect! The clue that is helpful, here, is that there is a delay before the secondary burning commences after the initial puff -- it takes a couple of minutes for the exhaust gases to get the cat and muffler hot enough to start burning off the collected oil.

Brad,

My suggestion is to unbolt the catalytic converter, pre-muffler, or test pipe ... and examine the inlet and outlet for oil seepage and pooling, and the inlet to the muffler as well!

[88911inga]

Warren,
Thanks I guess I'll get prepared to do that this weekend. Are there any gaskets in line there that I need to get to do this? Pardon my ignorance, I still don't have the Bentley manual yet.
All of you that helped with this, thanks very much. Brad

[ianc]

When the oil seeps past the exhaust valve guides with the engine at rest ... it never goes into the combustion chamber!

Sure, but what about the intakes? There is negative pressure on these actually pulling oil through into the combustion chambers!

ianc

[KillerDynoSoar]

Originally posted by Early_S_Man
Brad,

3/4 way up on the dipstick is a bit high for the oil level ... 1/4 - 1/2 up on dipstick is optimal. Remember -- there is a two qt. range between upper and lower marks on the dipstick ... and even at the low mark there is over 9 qts of oil in the system, i.e., it isn't at a danger/low level!

My suggestion is to run the oil level at the 1/4 - 1/3 way up between the marks on the dipstick for a while and see if your consumption 'problem' goes away??? By 1988 the factory had presumeably solved the problem with premature valve guide wear due to the orange elastomer valve stem seals, and 80K would be too soon to be showing valve guide problems. Your worries may be needless!

ps,

If the smoking is only at startup, and completely disappears after a few minutes of warming up, then it really isn't a problem at all!
Do a search on the string 'smoke at startup' and you will find many, many threads on the subject ...

http://forums.pelicanparts.com/search.php?action=showresults&searchid=2024783&sortby=lastpost&sortorder=descending

GOSH! I am having the exact same issue right now with my 3.2 engine. It puffs on start up and then clears right away. Then nothing until its good and warm. I did find though that my car would smoke after a really long run alittle on idle. When you blip the throttle it would go away.

However I did notice that this happened since when I topped up the oil to the FULL mark on the dipstick. Perhaps alittle over fill???

My engine is of unknown quantity however and I assume it must be valves.

Interesting thread and I look forward to whateveryone suggests.



BTW: I am off to Le Mans Classic next month... I hope driving my car with valves that need doing won't cause any damage other than the embrassment at idle time to time. ???

[JeremyD]

Try running the engine hard - I mean to almost redline and then letting the engine brake the car (creating a vacuum) - then at idle see if it smokes. Mine did this and it turned out that all the exhaust valve guides were worn well past spec and had to be replaced - one intake valve guide was worn bad enough to make a little oil on one of my plugs - and my car had 56000 miles at the time.

650 miles per qt is still within porsche spec - but definitely on the high side.