nice color.

your DV test was good and your WUR test was good. your pressures are on th low side but OK. i would like to see 5bar and 3.6 warm, but don't go change it just because of that.
i think i would move on to some thing else.

it still sounds like the DV may be hanging open. i would either remove it and plug the lines or at minimum i would remove the control line on the top that opens it. it tested fine but it could be sticking.

verify the vac connection from the WUR.

Cold start in the morning.........
 

Gregory,

You are doing the test like a pro. Since you are doing all the troubleshooting and rely only on your feedback, I like to request additional information. Let the car sit overnight with the CIS pressure gauge kit hooked up.

Put the car in neutral and start the engine. Do not touch the accelerator for this test. Best way to do this test is to open the driverside window and reach for the ignition switch from the outside. Try to start it with no assistance from the pedal accelerator. Note how many attempts before you get the car to start and record the cold engine RPM the very instant it began to run. Take a quick look at the pressure gauge. Record also the ambient temp.

Observe the engine RPM change (delta) from initial till it stabilizes below 1000 rpm. Keep us posted. Thanks.

Tony

Test
 

Thanks for the feedback. I'll try the test, but it will probably be a few days until I get to it. Only issue is that sometimes my tach acts up and seems to read 1/2 the actual RPM (did today when I started it). Just from past experience the car always starts fine with no throttle input, revs up a bit, maybe to 1400 rpm, but then almost immediately goes to running poorly, maybe 400 rpm. It almost always sorts itself out after a minute or two and normally doesn't stall, but is undriveable during that time period.

Anyone have link to a good video of a CIS car cold start with a properly tuned system?

From everything I've read a properly tuned system should just start right off the key on a cold engine. Turn the key and vroom. Hardly any cranking if any at all. I'm trying to get mine that way :).

Video of Cold Start
 

I let the car sit overnight and this is a cold start with the car in neutral and only turning the key, no other intervention. You can see that it starts well initially then the idle drops down and it runs rough for a period of time. This was not to bad, sometimes it is worse, and periodically it stalls.

https://youtu.be/yj2CW737F7Q

After the first video I shut the car off and immediately restarted it, you can see a more normal start and the idle slowly drops down closer to the normal idle position.

https://youtu.be/OCQ2N_LgfuM

I'll hook the fuel pressure gauge up this afternoon and let is sit overnight to look at the fuel pressure on the cold start tomorrow morning

Country Drive
 

Here is the car in action, just playing with the new Gopro

https://youtu.be/XIDKdHz6ers

i did not see any problem other than the tach jumping around at first. do you have an MSD.

one of the bad things about CIS is that the warm up time of the WUR and AAR is not long enough.

if it idles and runs fine warm, starts fine when cold and hot, fuel pressures are ok but it jsut runs bad between cold and warm you could try richening the mixture a very small amount or just leave it.
my 77 was kind of like that on very cold days. the warm up time of the WUR and AAR was not long enough.

one other thing, if you still have the thermo time valve (TTV) that is only active for about 20 seconds. on your car that will have a .5bar change that leans it out. the TTV was a great add on they did that really helped cold starts and backfiring.

You got it backward my friend........
 

Ty,

My good friend from the South. I think you got it backward.
1). Both the WUR and AAR in general take about 3 to 4 minutes from cold condition to warm condition. This time is actually too long compared to modern engine technology. Observe your late model cars and they would idle cold high for several seconds and drop quickly to idle speed in less than 30 seconds. The WUR and AAR could establish the warm state conditions much faster than the 911 air cooled engines. The CIS in water cooled engines like in Mercedes Benz and others do not suffer from this kind of problem.
2). The TTV (thermotime valve) is not active the first 20 to 30 sec. from a cold start and stays active until the FP stops. You got this one backward too.

BTW, thanks for the information you sent me earlier.

Tony

My 81 SC had the similar problems. Hard start after warm; hunting idle after warm; some stumbling/roughness at times. Does you car have an O2 sensor? Mine was replaced and had the fuel mixture adjusted and that took care of my problems.

based on my 77 with everything working properly, the time the AAR was open was not long enough. same with the WUR. when it was really cold out the AAR needed to say open longer and it would have been good if the mixture leaned out slower. yes everything was working as it should. this is just my opinion.

the TTV is closed for the first 20 seconds when you start the car. this blocks the vacuum to the WUR to make it run richer. after 20 sec or so it opens and the vac raises the CP to lean it out.

O2 sensor
 

My car does not have an O2 sensor. Believe those were added in 1980.

Greg

I am having the same problem with mine - it started acting up after I swapped out a WUR. The one that was on the vehicle was working just fine but I was having a "fuel economy" issue. Getting around 17 MPG around town.

So I decided to change it out which was s dumb thing to do. The back up WUR came from a junk yard but I set it up so it was adjustable. Did the same with the original one.

So I screwed things up and as soon as I get time I will tackle the problem. That's probably where your problem is.

When I first start mine up it immediately goes to 2000 rpm and then within a few seconds drops down below 900 RPM. If I step on the accelerator and bring the RPM's back up to 2000 and hold it there for about a minute it will idle on it's own but still around 900 RPM - I usually like to keep mine around 1100 RPM because of the AC.

I think mine is going to be a fuel pressure issue as may very well be what you are dealing with. I need to get my other car project completed so I can pull the P-car into the garage to work on it.
Hope this info helps.

Fuel pressure on cold start
 

I hooked the fuel pressure gauge up the other day and started the car up to make sure the fuel pressure was normal before letting it sit for the cold start test. The car sat two days after the initial gauge installation. The video below shows the fuel pressure on a cold start with the car in neutral with no other intervention, only turning the key. The valve on the pressure gauge setup is in the open position. The ambient air temp. was around 60 degrees F.

https://youtu.be/crsSzjFkLxw

Cold start video..........
 

Gregory,

The engine started right away and the cold control fuel pressure was changing like it should. However, it did not look like the warm control pressure ever exceeded the 46 psi. mark. If I remember correctly, your system fuel pressure was like 4.6 bar (66.7 psi.). If you re-set the system pressure higher to 71-72 psi. the warm control pressure would go up probably like around 51-52 psi. I like these numbers and I could easily remember these values when I do a calibration work.

One thing I like to see was the engine RPM during the warm up period. The control pressure versus time is good. WUR is working great except the FD needs some adjustment or calibration to get the warm control pressure on spec.

Nice video.

EDIT: There is a serious mistake in the above post which I did not delete. Nor corrected. Setting the system fuel pressure higher has no effect on the WCP. Surprised no one detected the error.

Tony

Fuel Pressure With RPM
 

Here is a video of the fuel pressure on a cold start with no intervention other than turning the key with the RPM displayed. Multiply the RPM value by 10 to get actual RPM. At 2:35 I close the valve between the WUR and fuel distributor an you can see the pressure go up to about 4.6 on the pressure gauge. Every time I try this it seems to start better?

https://youtu.be/NPNuc6biNQ4

High Idle
 

Here is a video of my high idle issue. I had just gotten off the highway after driving 40 miles and was siting in stop and go traffic. You can see that I drive forward a bit and then when I stop around 14 seconds in the idle just sits about 1800 rpm and then eventually drops down to 1100. Normally it idles abut 900-1000 and many times the idle doesn't drop down at all when this happens. It only does it when the engine is fully up to temp.

https://youtu.be/8wK8alRrxR8

Gregory,

I have a '78SC and exactly the same symptoms as you do (as described here on pelican: click).
Have you found out what it is/was or found a fix?

Not fixed yet
 

I have not resolved it yet. Got busy and haven't had a chance to get back to it and when I have time I've been driving it instead. I think my next steps will be to pull the AAV out and test it. I checked the AAR already and it works as supposed to. Somewhere I'm getting air past the throttle plate. I want to get a wide band O2 sensor and check my mixture also. Prior to all this I replaced some leaking injector seals, which fixed other problems, but have no idea where the mixture had been set. Don't know that that would have an impact, but is worth checking. I'd be curious to start someone else's car and see how it behaves, it sounds like this is a common problem with these and surely they didn't run this way from the factory? Unfortunately this is my first 911, so I don't have any point of reference for what is good. I'll post something if I find a solution.

Greg,

Summitracing has the sensor and gauge - both for around $60.00. I just purchased one for the 71 TR 6 convertable I am working on. Here's the part number

Sum G 2986-1 gauge, G 2989 sensor. You can probably purchase similar gauges on e-bay for less.

Gregory,

Is your car a UK delivery car? Never mind the position of the steering wheel.

I had an SC in with the same symptoms.

Do you know how to accurately set the CO level? If you do there is a quick and easy test to see if we can get improvement on the sumbling at cold.
What is the current CO level?
Post a picture of your "045".