See if you can diagnose the problem...

Keep in mind that I'm talking about a 1987 911 Carrera with 55,000 miles. Last summer the oil consumption was about 600-700 mi/qt. Car smoked a little on some startups and let out a bit of smoke upon hard acceleration from 1st to 2nd (between 5000-6000 rpms).
This summer I replaced cat. w/ a bypass pipe, and within a month began to notice more and more smoke (these two may not be related). Exhaust began to smell a bit rich. Oil consumption dropped to less than 400 mi/qt. There is a small oil leak onto the heat exchanger (passenger side) that doesn't get to the ground (just enough to give off a nice burining oil smell).
When warmed up the car will not smoke while idling, but as soon as you start off from a stop a nice cloud of smoke pops out. Not any smoke noticable while driving, but sometimes a bit upon deceleration.
There's no audible valve noise, and mechanic turned up nothing when he checked for valve guide wear 3k miles ago while performing a valve adjustment (although I'm not too sure about his ability).
Motor keeps fouling plug on Cyl #6 (plug is black and sooty, a little wet, but not dripping). The remaining 2 plugs on that bank look slightly used, but the 3 on the other side are perfect. Car runs fine after replacing plug (until it fouls again). New magnecor ignition wires approx. 3k miles ago.

So what does this sound like? The dreaded valve guide wear, broken head stud, piston/ring/cyl problem... other?

Just trying to diagnose the problem before I begin worrying about how to pay for the "Fix".

Thanks,
Dan Tolley
1987 911 (ole' smokey)

It does NOT sound like an oil consumption problem to me ... the oil usage figures cited in the factory spec book, allow up to 2 liters (2.12 qt) of consumption, not leakage, in slightly over 621 miles. But, that kind of oil burning in the engine past valve guides, rings, etc. produces constant blue smoke while running, not just smoke upon acceleration!

I think you need a CO meter (check the recent thread on that subject) ... which needs to be used both for static checks, and running checks during a driving test!

And, a drive-by check by someone else with a camera, digital or 35 mm, to document the color of the smoke upon acceleration, might be useful, too! I suspect you will find the smoke cloud to be gray or black, not blue, hence you need to find and fix your oil leaks, and adjust/fix your mixture problems! Some oil leaks are dynamic in nature, and do not produce any noticeable puddles while the car is sitting overnight.

I recommend you get a copy of the new Bentley service manual for the '84-'89 Carrera's! A copy of Bruce Anderson's 'Porsche 911 Performance Handbook,' and, of course, Pelican's CD-ROM wouldn't hurt, either!

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Warren Hall
1973 911S Targa


[This message has been edited by Early_S_Man (edited 08-28-2000).]

I would think the plug and oil leak problems unrelated

After dropping my motor for my trans rebuild I found the major source for my persistent oil leak on my exchangers

THe oil thermostat on the engine has a O ring seal that with age got very brittle and shrunk ,hence it had a sizeable leak from it ,coupled with a few loose bolts on the oil cooler cover caused oil to leak to the cooler plugging it up in spots on the top of it
As you accelerate or hit the brakes it causes the oil thats pooled up in the various spots on your motor to run out

Unfortunately the only way I can see to fix the Oring on the thermostat is to drop the motor

I have a copy of the Bently Manual on it's way. I also ordered a cd-rom from Pelican about 3 months ago (still hasn't arrived).

So you're saying my "smoke" is NOT related to valve guide wear or piston/ring problems? Then what would cause the one plug to foul, while allowing all the rest to remian perfect... faulty injector? I've run techron through the system 2X (no noticable results). What would cause the smoke (which is grey to white, and while it smells oily, also has a faint rich fuel odor) only upon acceleration/deceleration and not while simply idling? Could the 02 sensor be responsible (perhaps damaged after changing the cat). The amount of smoke emited increases after the motor reaches 190+ deg F.
While in for service (3 months ago) my mechanic found the fouled plug on #6 and tested the ignition wires (he said #6 was bad) and I replaced the wires with 8.5mm magnecore. 2 Months later I checked the plugs and #6 was again fouled (black, oil like residue).

I've removed the K&N filter and put back the OE filter. I might even put the cat back on... What things can I do easily myself to try and isolate the problem. What things should I ask my Mechanic to do?

As for the oil leak, I'm not too bothered by it. Perhaps it's the oil pressure switch on the front of the motor. I'm usually so involved with other things that I forget to run my hand around behind the throttle assemble to check for leaks.

oil usage is about 325 mi/qt. Maybe it leaks about 1 tablespoon/week (not enough to make a difference). You're right about the leak. There is not dripping on the ground. It just collects on the side of the motor and exchanger. I don't think the smoke is coming from the oil leak, it comes out the tail pipe.

The car still runs superb, and if I never look in my rearview mirror everything is perfect :-)

Thanks,
Dan Tolley
1987 911 (ole' smokey)

Just my 2c worth.

I had a problem like this years ago with a 2.4 motor. One cylinder was always fouling the plug, smoked a bit and finally started losing compression. I had just purchased the car and did not know much of the past history.

Could not figure out the problem and finally gave up and found a 2.2 motor to swap in its place. Once I had the time to start tearing the old motor down I found that (the car had been sitting for a while) a mouse had made a nest inside the motor on top of the left hand forward cylinder between the shroud and cyl head/cylinder. It had crawled inside the shroud by going into the fan inlet then to the back.

The cylinder, piston and rings had been baking for months because of lack of cooling air while I drove it thinking that all was OK.

Any chance you may have the same thing? Or a plugged up fuel injector in that cylinder making it run lean and thus hot?

Just passing my past history... never would have guessed this one.

JoeA

I would not put the CAT back on, at least not just yet. the smoke could clog it.

I suppose an internal engine part could be to blame (ring, valve guide etc), but 55,000 miles seems too 'inexperienced' for this. Just for kicks I might check this #6 ignition wire again as it may not be within spec.

If the valves are adjusted, the injector is working and the ignition system is fine, then I might consider a hotter plug for that cylinder. This will stay clean longer.

A compression and a leakdown check can pretty much answer any questions about internal engine parts. ALL these are tests you can do yourself.

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'83 SC

Curiouser and curiouser, as somebody else once said!

I suspect a 'stuck open' #6 injector, as your smoke that smells like gas, and wet, black fouled sparkplug sounds, and I bet smells like gas, too, if you pull it out quickly after a test run!

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Warren Hall
1973 911S Targa

My '88 911 displays some of these symptoms. The smoke only occurs at startup, EVERY startup. On cars I have seen with bad guides the smoke occurs once the car has been sitting for awhile, but then repeated starts (within 15 - 60 seconds apart) do not produce much smoke. My car, however, smokes every time. Is is possible to replace the SEALS without removing the engine? By the way, no leakdown or other tests have been performed yet. Thanks for any suggestions...

Another good call by Warren who said earlier taht the smoke color should be positively determined. Oil smoke is a very distinctive pretty blue color. While I've heard that the 3.2 engines can have valve guide issues, I really doubt that oil will drip past them instantly, so that oil is burned on EVERY startup. I suspect the smoke is darker, indicating a very rich mixture.

Warren's got me thinking about whether you style of injectors (with the litle solenoid) can fail and be always open. This is promising.

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'83 SC

As I stroll through the records left to me by the previous owner, what should I find... replacement of one fuel injector. No idication of which one, but I'll bet it's #6.
How does one go about checking for an "open" injector. I figure it'll be easy to check the new ignition wire, but I doubt that's the culprit (the chances of a bad wire being replaced with another "new" bad wire are slim). What about the dist. cap? I didn't replace that. Might that be responsible?
I'm also sure the car sat for some time at some point in it's life (55k miles for a 13 year old car), so it is possible that some "critter" has nested in the shroud. How could I check for this???
As for checking the plug after a quick test run... I'm not too keen on shoving my hand back to #6 after the motor has warmed up. I like the smell of cooking meat only when it's coming from the BBQ grill.

Here's some more data for those of you who consider yourselves 911 sleuths.

The PPI I had performed at 45k miles revealed the following. Compression was from 180 to 170 (#6 was the lowest) and the leakdown ran from 4.3% to 7.1% (%6 also being the highest).

People can flame Warren all they want, but it seems to be he's got a pretty damn good working knowledge of 911's.

Thanks more,
Dan Tolley
87 911 (ole' smokey)

I had a similar experience with my 86 Carrera, high oil consumption and fouling plugs. But the problem wasn't the valve guides, it was the rich mixture it was running.

Somehow rich mixtures, smoking and high oil consumption seem very closely related because since I had my mixture set properly, I no longer get the familiar puff on start up, oil consumption went way down and my plugs no longer foul while my performance went up.

I even overfilled my oil tank by mistake one time expecting it to smoke like crazy as it would do in the past only to have it run normally without any smoke as I cruised down the highway with my oil level gauge pegged.

Regards,

Joe Garcia

[This message has been edited by stlrj (edited 08-29-2000).]

[This message has been edited by stlrj (edited 08-29-2000).]

I have an '88 Targa and I have about the same level of consumption (400 miles/qt) with no leaks. I have noticed that the consumption is greater if:

I operate at a constant speed (ie cruise control set at 75 mph or around 2800 - 3200 rpms) for an extended period (2 hours or more) of time.

The tank level is below 1/2. It seems to drop slowly to about 5/8 (say 250 miles)and then it really starts to go.

In addition, I have noticed that the #5 plug has a tendency to foul.

Any suggestions?

So Joe, did you get your fuel/air mixture set at a Porsche dealer? What was the bill? I doubt that I'm up to anything that technical as a DIY.

Dan Tolley
1987 (ole' smokey)
perhaps soon to be a clean running 911...

Dan,

Unfortunately, I'm a hoplessly anal "do it yourselfer."

But if you happened to live nearby, here in Novato CA (home of Excellence and SSI), I would be happy to set it up for you and have you drive my car to see what you think.

Another option would be to purchase a new factory adjusted air flow meter and see if that helps.

Regards

Joe Garcia
86 Carrera

To find mouse nests, you might need to remove some stuff and/or poke a wire up between cylinder fins. Snoop around, in other words.

To see if an injectors is spraying all the time, maybe you could pull the injector and place it in a jar with the fuel and electrical lines hooked up to it, run the fuel pump (unplug the fuel pump relay and connect the appropriate terminals), and see if it sprays. I suspect that the injector shoudl be closed at this point and not spraying at all.

I would not necessarily trust a new electrical item, including ignition wires. Probably the #6 wire is fine, but this is not guaranteed. A friend, experienced in mechanical stuff, told me the other day that he has found more 'bad' condensers in the shelf in boxes, than in cars. For example. And if Warren has a comment on this topic I'll appreciate hearing it.

And on that subject...Warren has been 'flamed' before and can take care of himself. I predicted, and was happy to observe, that his reaction is always the same. He walks away...

Your compression and leakdown tests are beautiful and you can quite worrying about internal engine parts. I'd fly an airplane with your engine in it.

Finally, if you have not changed yoru cap and rotor recently, DO THIS NOW.

Injector or ignition wire (or bad terminal in distributor cap). This is where I would surely focus.



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'83 SC

It probably wouldn't be a bad idea to have a spare injector on hand, whether you find a bad one this time or not, and that would seem to be a quick test to swap out with a new one and see if the smoke goes away. Considering the popularity of Bosch injection parts these days, you may even be able to find one locally at a NAPA or other parts store! When your Bentley manual arrives, or if you happen to have the factory manual, procedures for relieving fuel rail pressure, then removing the injector should be carefully followed!

There are probably a couple of ways you could test a suspected bad injector after you have removed it from the engine:

1. A regulated source of 33 psi compressed air could be plumbed to the injector ... any hissing or noticeable leaks are unacceptable!

2. An authorized Bosch 'service station' for fuel injection will be able to test the injector for static leaks and spray pattern.

An overnight stint in an ultrasonic cleaner in a carb./injector cleaner like B-12 Chemtool might loosen any internal contamination by rust, or particulates like Carbonates (white non-soluble compunds that can settle-out inside fuel injection systems in ALL THE WRONG PLACES) sometimes passed along by careless refinery or transport truck carriers.

Please NOTE: Any time the injectors on one side's fuel rail are taken loose, it would be a very good idea to replace all of the O-rings on those three injectors connecting to that fuel rail, and the bottom sealing O-ring of any injectors removed from their cylinder head!

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Warren Hall
1973 911S Targa



[This message has been edited by Early_S_Man (edited 08-29-2000).]

So lets see ...
I need to get a new cap& rotor, at least 1 new fuel injector, and test my new plug wire. Good thing this BBS has a parts store :-)
I figure testing the plug wire will be easy. Just grab one of the old wires (not #6), unplug the new one at both ends, and run a shortcut from the dist to the plug with the old wire. If this is the problem I can re-route a new wire later.
The cap and rotor will also be easy.
The Fuel injector I have no idea about. I've read Bob Tindal's article on CIS injector removal... how much different is the removal of a motronic injector? Any tips or advice?
Do you suppose I should change the fuel filter while I'm at it...

Thanks again everyone for your help. If my problem is simply fuel related, the savings over a top-end are huge. Jeeze with that $$ I could buy a fabspeed muffler, MAF, & fuzzy dice for the mirror...

Dan Tolley
1987 911 (ole' smokey)

How does a bad injector cause an increase in oil consumption?

I am absolutely convinced that the problem is not inside the motor.

The spark plug wires should be tested for resistance. I don't know the spec for your car, but you unhook the wire from both the distributor and the spark plug, put the ohm meter's test leads at either end, and measure the resistance in ohms. Too many or too few ohms and your wire is bad.

Motronic injectors are also mysterious to me but I'd heed Warren's caution about relieving fuel rail pressure properly before removing injectors. Since you seem to agree with the spare injector idea, you might just get one, replace #6 and see if the problem stops. Perhaps have the old injector looked at by the shop folks, if their price is reasonable.

If this does not solve the problem I'd even suspect the electrical connection, or signal, to the injector. As you can see, I think you're about to find your problem.

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'83 SC

If the quantity of fuel being injected into one cylinder is so excessive that not all is being 'aerated' and mixed with air, then the excess mist is still in liquid form, in the combustion chamber, and tends to dilute and 'wash' oil from the cylinder walls, making a less-than-ideal combustible mixture, but combustible, nevertheless! At elevated operating temperatures, that gas-oil mix is burned, however inefficiently, resulting in a Blue 'smoke signal' mixed with the Black overlly-rich smoke cloud ... but the oil smoke is not too visible amongst the black cloud! Cylinder, ring, and piston wear tends to be accentuated under such conditions of a washed-down cylinder!


Hence, continued operation of an engine with an excessively-rich condition where you can smell strong gas fumes in the exhaust is not wise ... it may cost you a lot more than a few extra bucks at the gas pump, in the long run! I think Dan already knows that, by this time ... does everyone else recognize the danger?

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Warren Hall
1973 911S Targa

[This message has been edited by Early_S_Man (edited 08-29-2000).]