^^THIS^^

No, that is the idle screw!

The problem on all these documents is that most of them explain every components function but not so much how they interact and when or what time they're active. This knowledge you only get by working on the CIS. The only thing I can recommend is the CIS troubleshooting guide:
https://cis911primer.com/Troubleshooting%20Guide/Notebook%20Spiral.html

Here's s thread we had one year ago about sensor plate height, maybe this help you to underdtand...
https://forums.pelicanparts.com/porsche-911-technical-forum/1158127-air-sensor-plate-height-why.html

And now I have learned these are actually two different things. Thanks, as always.

As for driving through a couple tanks of fuel and additive, my mechanic has advised against that based on the current fuel mixture and smoke issue. So I guess the next step is double check/set the plate height and then smoke test for leaks? Maybe simultaneously getting the WUR rebuilt?

Do only one thing at the time. Otherwise you're running into trouble mixing up things and losing oversight.
And prove any bad part by testing it before replacing as todays parts quality mostly no more same quality as in early days...

In this thread we discussed in more detail about sensor plate height. This posting I added a sketch from Bosch tech instruction manual about CIS on how the sensor plate house is in detail:
https://forums.pelicanparts.com/porsche-911-technical-forum/1158127-air-sensor-plate-height-why.html#post12203447

Whole thread is worth a read.

I do understand the principle. I am expecting that when it’s warm enough here to compare pressures to the graph, someone will tell me my WUR needs rebuilding. But I won’t do that until confirmed. If the plate height is really just supposed to be set to a height and left, not adjusted or dependent on other factors, then that can be checked/done independently. If there are vacuum system leaks, those too should be fixed regardless. I guess I’m just trying to get back to baseline to then make proper adjustments. Seems to me there are only so many parts and fewer of them are “adjustable”.

Latest round of pressure testing, basically done at 10 deg C, the bottom of the temp/pressure charts.

CCP - 1.6 bar
SP - 4.55 bar
WCP
@ 4.5 min - 2.7 bar
@ 7.0 min - 2.95 bar

So it would seem CCP is a touch high. SP is in the lower end of the normal range. And my notes say WCP should be 2.9-3.1 bar, which it eventually is but maybe it needs to get there in 3-4 minutes instead of 7 min. Does it matter that it takes a little longer to plateau at that level? These numbers obviously aren't as bad as we originally thought. Doesn't feel to me like they are so out of whack as to be the source of hard cold start, rough early idling, and a poor air/fuel mixture.

Where do I go from here?

Check how many turns you need to fully close the idle screw. Turning CW closes the idle screw bypass, CCW opens it.

I wouldn't worry about the long.time to get the wcp in spec. I found the same.thing when performing this test on battery power and low ambient temperature. When I repeated the test with the engine running the WCP got into spec in about 3 minutes.

I would follow Schulisco's advice on checking the idle screw, and if you haven't already done so, get set up to do a vacuum leak test. There are multiple threads on how to do this, but let us know if you need a link. I wouldn't adjust anything until you confirm no vacuum leaks.


John

I'm going to make a few statements that others may not agree with. Here goes:

Low ambient temperatures may make testing the fuel pressures difficult. If you don't have a heated garage, it may make more sense to ignore that for a bit and focus on eliminating unmetered air until the ambient temperatures rise. The important part: Focus on one or the other - not both. If you start chasing air leaks then please ignore system pressure and control pressures for a while.

I have used two different methods to reliably find air leaks:

#1 - Smoke test with a smoke machine - Lots of threads here on that. Cap the exhaust pipe, remove the air duct and cap the throttle body, connect a smoke machine to a vac port on the air box, and watch for leaks.

#2 - Soapy water with the shop vac test - Remove the air duct and cap the throttle body. Connect a shop vac in blow mode to the tailpipe. Spray a little soapy water on all joints (including every air box seam and connection) and watch the bubbles.

CAUTION: For both tests, you want to limit the air pressure inside the intake system to a couple inches of water or else you will damage things.

You need to treat the air leaks and pressure issues as two separate issues. Fix one, then the other. Checking / fixing air leaks first makes sense as you then only have to set the idle/mixture and ignition timing once.

While you're in there, you can make sure the air flow metering plate rests where it should and is centered in the bore.

Everything from here on out assumes the air leaks are sealed (as well as they get).

Question #1: Did you ever validate your pressure gauge against another known pressure gauge? If not, please do so (just to ensure the pressure readings are meaningful).

My opinion (which assumes that you have a good, working gauge): Your system pressure is on the bottom edge of the limit and needs to be adjusted back up toward the 4.9 bar range as a starting point. CCP / WCP don't matter unless the SP is correct.

Question #2: Do you have vacuum applied to the WUR for your test? If not, you need to (and see the WUR chart for the correct vacuum amount).

The -009 WUR uses a vacuum enrichment system: Vacuum drops at wide open throttle, the control pressure drops, the air sensor raises a little extra, and you get richer fuel mixture when you need it.

Please retest with both vacuum applied and without and report both. It's relatively easy to do - Hook a vac pump to the vac fitting. Apply/release vacuum when cold and again when warm.

Summary for the next pressure test:

#0 - Wait for warmer temperatures and seal air leaks while you wait; put the air flow plate in the correct position. This won't affect the pressure test but it will affect drivability eventually and you will make progress.

#1 - Validate the gauge is good.

#2 - Get system pressure back toward the top end of the setting spec.

#3 - Test control pressures with and without vacuum applied to the WUR.

#4 - Report back.

Once we've got air leaks sealed, air metering plate in the right place, and a confident pressure test - then we can figure out what needs to be adjusted.

4 full turns to close the idle screw.

I believe the AFSP is in the correct position. At rest it is even with the lowest level of the Venturi funnel. So, I'm not going to mess with anything there for the moment.

Vacuum leak testing will occur this weekend hopefully. I will have to get my hands on a manual vacuum gun to redo pressure testing with the WUR under vacuum.

I did cross-check this, but in a not-so-scientific manner. I will do this more precisely in the next few days as well.

Thanks to all for the insights and suggestions thus far.

4 full turns is way too out by far. The standard setting is 2 turns open from fully closed. With that you're able to start the engine and it will idle when cold with an increased idle of approx. 1200rpms.
4 turns guide me to suppose that sth else is wrong making the mixture that rich.

When you say that the sensor plate/AFSP is set to the lowest end of the venturi funnel, does this complies with this? (bottom schematic)

http://forums.pelicanparts.com/uploa...1640702797.jpg

Thomas

Does it run well when fully warmed up and driving?

I'll say again: Spend some time driving it. Put a tank or two of fresh fuel through it (with Techron). You can continue troubleshooting and testing, but some of the glitches may clear up just from using it regularly.

So presumably something somewhere else was either adjusted or has failed, leading to an inappropriate correction at this idle screw. I'm guessing the list of possibilities is too long. Does that include vacuum leaks? Or will I likely be hunting down a part in need of a rebuild or replacement?

Yes. I am confident that the sensor plate is exactly where it is meant to be.

The honest answer really is, " I don't know". It definitely runs better, but it smokes and that make me leary of touring around town with it. I've taken it very briefly down the street and back. But I have zero experience with these cars and their engines, so I don't know what to expect. It is not yet been registered because up until recently it wasn't really running at all. If we're really following the rules, and I tend to be a rule follower, then I would have to register and have it inspected, which then means a list of other odds and ends like lights and seat belts, etc. It can and will be done, but it's not a quick process.

Uncle
 

After fooling with the CIS on my 1975 911S for far too much time I sourced a set of Weber 40 IDT carbs. When new the CIS system was unbeatable, but I just don't have the time patience to fool with it.

Carbs will be at my shop next week, rebuild about a week or so, install a couple weeks. Will be running just in time for spring

Hate to be a quitter, but also interested in enjoying my original paint example

Yes, it look's like.
Vacuum leaks - no. As the screw gives with 4 turns double the amount of bypass air to let the engine idling. Even when the mixture seems to be ok, but as you wrote that the engine still smokes. This can be caused by rich mixture as well as burned oil which is common for a flatsix engine after sitting long time. But also detoriated gas may cause this. Depends on the color of the smoke. How does the spark plugs look (color, wet or dry, dirty with black deposits etc.)? How does the fuels smell?

There may be several things to sort, but in the beginning the most important components of the CIS, WUR & FD must be proved okay. So we're back at the beginning.
As I still don't know if your measurings of SP and CP were correct - only when they we're proved correct it makes sense to move ahead to the next steps.
You wrote about your last test results of the CP. Basically they don't look too bad I would suggest to let the FD checked / overhauled by a CIS specialist as they're mostly dead after decades, even if they have been driven or not. They contain rubber sealings, metal sealings and are made of cast iron which can also corrode. The tools you need for overhauling them are highly precise machines you cannot buy at Home Mart...not to mention the experience. Expecially when you aren't experienced with these cars. I got mine overhauled by a specialist and he charged 800bucks 5 years ago...highly satisfied with the work, as the FD is the central component delivering the right amount of fuel to any cylinder under any operating condition which fundamental for a good running car...when some cylinders got too few fuel they run too hot. On an aircooled engine this may cause damages relatively quickly...

But before tearing the FD out of the car I would ask you to do one more thing:
When does your fuel pump start running? When switching ignition on?

The fuel is new. Most fuel related components are new between the tank and FD except for two polyamide lines. I call the smoke white. I have zero experience with labeling smoke colors though. I don’t think I can begin to accurately describe the smell.

These are the old plugs. Obviously mismatched. I have since replaced them with proper Bosch replacements.

http://forums.pelicanparts.com/uploa...1741313428.jpg
http://forums.pelicanparts.com/uploa...1741313428.jpg
http://forums.pelicanparts.com/uploa...1741313428.jpg
http://forums.pelicanparts.com/uploa...1741313428.jpg
http://forums.pelicanparts.com/uploa...1741313428.jpg
http://forums.pelicanparts.com/uploa...1741313428.jpg

I already had the FD rebuilt in the Fall. Wasn’t by a CIS specialist per se, but it was someone who specializes in Porsche, Audi, MB, and VW of this vintage. Certainly had familiarity with this part.

Fuel pump comes on when key is put to run position, one stop before cranking for start.

I'm reconsidering this. I don't think the CIS is your biggest problem, maybe not even a problem.

Instead, the oil burning would get my attention now. Those plugs you pulled out have a lot of oil on them, and the "white smoke" indicates oil burning. It's time to do a leakdown test.

If you want to keep chasing the CIS, I'll sit down.

My experience: Grey/white smoke when engine is still cold is mainly water steam due to unburned hydrocarbons equals too rich mixture, condensed water in the exhaust and detoriated gas. As the gas is fresh I suppose a combo of both rich mixture and condensed water.
If engine is warm and smoke is black the mixture is still too rich. When smoke is blueish on warm engine then it's burned oil...

https://www.autozone.com/diy/exhaust/smoke-from-exhaust#:~:text=Dense%20white%20smoke%20indicates% 20a,of%20which%20are%20good%20signs.

As the 911G has no cooling water within the engine it's pretty clear...

The problem is with idling only in the garage you won't get the engine and the whole oil system and exhaust that warm to get reasonable results...and letting idling or even revving it half an hour or longer annoys the neighbours...and even it's not recommended for the engine (oil pressure and lubrication and even cooling is insufficient)

Check the mounted spark plugs too to see what color the have now. I suppose they look pretty dark too as tge car hasn't been really driven since...

The fuel pump must not run with ignition on on later CIS cars. I remember that the early CIS on '74 and probably '75 too didn't have the security fuel cut off switch at tge sensor plate housing. Check yours if it has one or not. Its a greenish 2pin plug on the "backside".

http://forums.pelicanparts.com/uploa...1741347472.jpg

The security fuel cut off switch plug is here named as the air flow switch.

Peter,

I have the same thought. A lot of OIL is getting into the combustion chambers in all six (6) cylinders. Refurbishing the complete CIS for this motor will not prevent the smoking problem. A leak down test will tell us more where or what the culprit/s could be. It is surprising that you get the motor to start with all those fouled spark plugs.

Tony

One other thing I have not yet done is an oil change. In theory, maybe the last guy, who owned but did not really drive the car, topped it off but while cold and resulted in overfilling??? Wishful thinking I know, but I don't want to consider the prospects of engine rebuilds at this point.

I do not have the fuel cut off switch/plug on this model. That came post '75.

The one and only way to measure the oil level in an aircooled 911 is via the oil dipstick on a warmed up and idling engine with the car on an even flat surface ...

https://forums.pelicanparts.com/porsche-911-technical-forum/484679-1986-911-targa-oil-level-pressure.html#post4771356

https://www.youtube.com/watch?v=p_LjKjJEHNM

https://www.youtube.com/watch?v=mZPOb5TK9wY

http://forums.pelicanparts.com/uploa...1741366093.png

True. But I don't know if the prior owner knows that! That's my shot in the dark.

I particularly like the video of the guy describing a bag of extra blood at the hip, ready to use when needed.

I would not want to see plugs looking like THAT. Have you tried a leakdown? I would start there, your CIS could be perfect, but if the rings/valve guides and out of spec, they must be repaired first

Oil level is checked with a warm, running engine on flat earth

We are (for the time being) pivoting away from the CIS and looking into engine health. Leak down (and maybe compression testing) is theoretically happening tonight/tomorrow. Will report back with the results.

Stay tuned…

For what it’s worth, the new plugs (out for leak down) are here. Probably less than an hour of operation time, little to none of which was extended high RPMs…

http://forums.pelicanparts.com/uploa...1741389703.jpg
http://forums.pelicanparts.com/uploa...1741389703.jpg

McG,

The second spark plug from the top, honey on white porcelain. For me, there was a pinhole in the spark plug wire assembly below the dustboot. The car just wasn't running right, from cold start to hot. Just to warn you, I couldn't see a spark at night, close bench inspection caught the defect. Honey colored as well, looked exactly like yours.

Phil

For what it's worth,
If I recall correctly, JW recommends leak downs done on warm engines. Maybe you can't do the warm one, did not read the entire thread.

Now that you say that, I think you might be right. I recall seeing/hearing/reading a similar thing. I may do both for $%!@ and giggles. :p

Compression tests done today. All cylinders are at 150 psi +/- less than 5 psi.

I did reinvestigate the injectors and found at least one to not be atomizing well at all. Some of the others are questionable. So I think I’m going to replace the set.

Did you do a leakdown test too? Results?

Do the injectors start atomizing correctly if you lift the air metering plate? How do they look with the plate halfway up?

I haven’t done leak down because I’m not sure how best to access the crank shaft to position each piston for the test.

The injectors all fire with manual lifting of the plate. They atomize okay, as best I can tell through the hazy plastic wall of the graduated cylinders I have. But the patterns are a little questionable to me. I also don’t have a good means to know if the pressure point for opening is correct and within spec, hence the decision to just replace them.

What I've done for leakdown testing: Pull ALL the sparkplugs at once. I've been successful at squeezing the belt while rotating the fan pulley with a wrench (carefully!) and that's provide sufficient friction to turn the crank. A dowel in through the spark plug holes confirms the piston is at TDC.

My plugs are already all out. That’s a good idea. I will try that. The dowel trick sounds slick! Now I just need a pulley wrench….

The crank pulley has marks 120 degrees apart that indicate when the pistons are at TDC. The remaining question is when each piston is at TDC at full compression. That will become obvious when you hook up the leakdown tester.

Next item: The leakdown test may not tell you where the oil is coming from. Specifically, if the intake valve guides or seals are leaking oil, you will measure more or less normal leakdown numbers. But let's see what the test shows.

The nut on the alternator is either a 22 or 24 mm.

Limited experience here... a couple years ago, I bought a 3.2 engine to rebuild as a project.
I wanted to test run it first so I put it on my test stand... it started and ran 'well'. But after a couple minutes running, it would start to blow a LOT of white smoke.

The next day I started it cold... seemed perfect.. after it got a little heat into it, it blew more and more white smoke. It never cleared so I rebuilt it.

The machine shop found that the valve guides were SO worn, that the valves had so much movement in them, that the seats were concave. Pretty sure this was the source of my white smoke. New guides, new valves and new seats.

After the engine was rebuilt, it ran perfect and never blew smoke.

My understanding is that blue smoke is burnt oil and white smoke is unburnt oil. A bit like a plane signwriting in the sky... not sure if that's a good analogy.


On another engine I worked on, it blew white smoke when the engine got HOT. Turns out that the engine had been sitting for a LONG time and had also been overfilled.. so much that the muffler got oil into it. When the muffler got hot, it made the oil smoke... I changed to a known good muffler and the engine never blew smoke. So in the end, I tried to flush out the old muffler, and then I just ran it and ran it till all the oil was burned out of it!

There are oil rings to keep things tidy, minimize oil leakage into the combustion chamber and there are compression rings to provide the pressure for combustion. A leakdown will ONLY test for the compression rings.

It's very possible the compression rings are ok, but the oil rings are clogged from overheating or excess contamination from dirty oil