Ok, folks -

First let me say thanks to all those that have offered advice and insights. It is definitely helping me understand the idiosyncrasies of these engines. This is my first Porsche and I'm just trying to take the time to learn everything I can.

If anyone is still paying attention to this thread, I posted a video on YouTube showing exactly what the car is doing from cold start. The car sat overnight.


tirwin,

I watched your video. That is precisely the behavior I described in post #11 and everything you need to solve the problem is in that post. Good luck.

Now, my wrench wants that line connected, so I'm in a bit of a quandry. What seems plain, though, is that without it, the car starts better and off-idle throttle response is a whole lot improved


5string,

Maybe he wants to reconnect it for an emissions test. The vacuum retard is a device to reduce HC emissions at idle to meet a specific test. Porsche made a compromise of settings to meet the test and still have decent drivability when the engine was new. Unfortunately, CIS lambda does not have active idle control and ECU controlled timing to compensate when the engine ages like a modern system and you have to find the right compromise of settings for your engine through tuning.

I subscribed earlier, very interested in your progress and updates. My car starts/reacts almost precisely the same as yours. Although I've come to live with it for several reasons. One of these days I'll get a set of gauges and re-request boy911's advice w/ some numerical data to report.

Morbid curiosity, if you take off the air cleaner and depress the air valve arm for a few seconds w/ the key on before cranking, does it start right up?

I have 2 likely suspects and a side issue with mine (seemed to start easier when ambient temps were in say 50's, now that we are in 80's 90's it's a little tougher, I have theories...), interested if your follows the same paths

psalt,

Thanks for the reply. I had forgotten about your original post. I guess I was so focused on the CIS pressures and the WUR that I didn't fully appreciate the wisdom of your post at the time. Now I completely get it. :)

So here's what I'm going to do. Remaining parts for the tune-up are coming in at the end of this week. It will probably be next week before I make any more progress.

First, check for vac leaks. Boyt911sc offered to send a procedure. I'm expecting to find that at least one or two injector o-rings are leaking and possibly some other places. Once I get that fixed, I'll move on to the tuning you suggest.

When I do the tune-up I'll check the condition of the plugs and check dwell and timing as you suggest.

One question I have is this -- I have been repeatedly cautioned that having the proper exhaust gas balance is critically important. Since I don't have an exhaust gas analyzer, I don't have a way to measure the effect of changing dwell, timing, mixture, etc on exhaust. What do other DIYers do in this situation? Gunsons seem to run around $200. How accurate are these units? Are they worth the money? Is this a MUST have or a NICE-TO have for the average DIYer?

tirwin,

When you are confident that your pressures are correct and you have no vacuum leaks with a propane torch, the duty cycle of the FV gives you an accurate proxy of the average mixture and allows you to make adjustments without a gas analyzer. I have confirmed this with a CO analyzer and a wide band 02 sensor. CIS lambda is correcting the mixture back to stoich at idle if the system is working properly. If the closed loop duty cycle is high, the open loop mixture is lean and the system is bleeding off lower chamber pressure to richen the mixture. If the closed loop duty cycle is low, you know the basic setting is rich and the system is raising pressure to lean out the mixture. The system is very accurate around stoich and once you know it is working correctly, it is very easy to make accurate mixture adjustments. Since the system corrects the mixture at idle or cruise, these adjustments really only effect the average mixture in open loop, i.e. WOT or cold running. If the engine is running, reading the FV duty cycle for 5 minutes will give you more information than a week of guessing. Unfortunately for your issue, you have only one shot at a cold start a day if you are striving for the factory drivability of instant firing and high cold idle at the first turn of the key without throttle. You make a small adjustment after the car has been driven for a few miles, then you wait a day to test the result. Disconnecting the vacuum retard and resetting the timing is the first step before any mixture adjustment. Most SC's with CIS lambda that stumble and stall at starting cannot tolerate a slightly lean mixture when the retard kicks in and kills the idle. Without an active idle control and ECU timing, there is no one to catch it. That is when you try to do it with your foot and cause other problems.

Time for an update...

I finally gorgeous time get back to the car. Sprayed carb cleaner at injectors, intake manifold and any other place that had a vac line connected. The only place I could find an obvious indication of vac leak was at the intake.

One of those smoke machines would be really handy right now. :(

Someone suggested using compressed air. I assume this would involve disconnecting the intake manifold and making some kind of adapter to connect the air compressor hose and seal the opening? If anyone has any details on that, could you please post it?. I'm really not confident I've found the only leak.

gorgeous = got

stupid iPad auto-correct

For pressure testing the manifold you cold use one of the adapters from the following site.

Intake Leak Pressure Tester

Just hook one of the appropriate size to the manifold intake and pressurize with compressed air from a tire inflation nozzle. You could probably use a bicycle pump if you don't have an air compressor.

J

Thanks for the tip!

Hi
i am also interested in testing for air leaks, but not sure where to connect the air line or pump, any pics ?
When I remove the oil cap the revs only drop 50-100 rpm?
thanks

***UPDATE***

Well, folks... I'm long overdue for an update. Sorry it hasn't been sooner. Unfortunately family and work sometimes comes before p-car obsession. And I know what some of you are thinking... I need to get my priorities in order. :)

First, a little recap...

I started this whole thread with what I described as a cold running problem. Car starts fine, but then sputters, chokes and wheezes until it stalls. Giving gas after ignition and keeping RPMs up around 2k for ~30s was the workaround. After that it was fine.

Other facts about the car:
- PO stated O2 sensor was disconnected so it constantly runs in open-loop
- PO also stated that AFR was set "a little rich"
- 65k miles on the car (no rebuild on the engine)
- car has had about ~10k miles put on it in the last 10 years
- vac line to decel valve is disconnected and plugged

Initial step in troubleshooting was to check the CIS fuel pressures. Everything checked out ok.

Checked the WUR. It was working correctly.

No joy in finding the problem. I was scratching my head. A lot.

Some people suggested it was the fuel distributor. Others said it was a vac leak. And even others said it was a tuning problem. All by the way, are very likely suspects.

First the good news. As I write this, the problem <knocks on wood> is solved. (Crossing my fingers, holding a lucky rabbit's foot, throwing salt over my shoulder...) I hope my declaration of victory is not premature, but it sure looks that way right now.

Now the bad news.

I have absolutely no idea whatsoever what I did EXACTLY that fixed it. There. I said it. And I'm not ashamed to admit it. I am confused. I am of course happy that it seems fixed, but that little engineering voice in my brain is screaming that it must understand how this happened. Theory, meet Reality. Reality, meet Theory.

This past weekend I did a tune up, so I did several things. Here's what I did and found along the way.

- Drained the oil. Not bad. PO said he used Mobil 1 15W50. Minor amount of debris on the magnetic tips of drain plugs.

- Oil drain seal at the crankcase looked to have some seepage. Removed the cover and checked the screen. Very clean! Only one gasket though. Supposed to be two. Installed in the following order: gasket, screen, gasket, plate. Installed new washers and nylock nuts.

- Installed new Mahle oil filter.

- Removed upper & lower valve covers. Saw a lot of oil build up around the outside. Seems like there was some leakage. Cleaned it up so I could see if comes back later. Gaskets were brittle and mostly snapped off in pieces in my hands. I had to be extremely careful with removal.

- Adjusted valves. Hardly any adjustment needed, if any.

- Pulled the old Bosch spark plugs. I was expecting to see plugs on the fouled side, but they were a nice tan color at the tips. None seemed noticeably better or worse to me, but I don't do this for a living either.

- Installed new NGK plugs.

- Replaced OEM plug wires with a new set of Clewetts.

- Replaced the rotor and cap.

- Installed new VC gaskets and used new washer and nylock nuts.

- Put in 9 quarts of Mobil 1 15W50.

- Installed a new air filter (actually did that about a month ago).

By the way, I wasn't expecting this to solve the cold start problem. I was just doing it because I figured that if I was going to muck with AFR and timing, I should start with a good baseline and I wanted to have a good maintenance checkpoint anyway.

So I did all this work thinking I was going to run it for ~30s at first just to check for any leaks. Dang if it didn't fire right up and idle perfectly at 1k RPMS! It has NEVER done that in the 5 months I've owned it.

After I got over the shock and amazement at what I was seeing, I checked for leaks. None. Excellent!

Turned the car off and waited a few minutes. At this point, I am now questioning to myself whether I saw what I just saw.

The next test was the real biggie. I started the car again. And it started! In the past if I turned the car off before it was good and warm and then re-started it, it was VERY hard to start. Definite improvement here, but still might be a fluke.

I let it sit over night. The next morning I started it again and it started right up. Wow. Took it for a test drive. No issues.

This evening I started it again and went for another test drive. Still no issues!

So what fixed it?

I haven't checked the timing yet. I'm almost afraid to change anything else at this point.

Well, I'm happy that it seems to be running better of course, but not knowing how I fixed it drives me farkin' batty.

Just want to close this post by saying thanks to everyone out there who chimed in to help a newbie like me. This is a great forum and fantastic resource. I'm always amazed at how people are willing to share their expertise and experience. I could not have come this far by myself. That is for sure!

I could've taken the car someplace and said "fix it", but there sure is a great deal of satisfaction that you get when you are your own wrench!

Stay fast my brothers (and sisters)!

One more thing I forgot to mention... I need to give a shout out to Wayne for this website and the parts! I bought everything I needed from Pelican and the 101 projects book was at my side the whole time!

Ambient temperature.

Glad you got it sorted out so easily. As an engineer you should know only to make one change at a time. No worries, just drive it and be happy.

*** UPDATE ***

I'm proud to say this case is closed!

For those of you who might be late to the thread, here is the original video I posted showing my cold running problem:

&#x202a;1983 Porsche 911 SC with Cold Running Problem&#x202c;&rlm; - YouTube

Here is the video I took this afternoon of how it runs now:

&#x202a;1983 Porsche 911 SC - Cold Running Issue SOLVED!!!&#x202c;&rlm; - YouTube

Took it to German Car Repair in Roswell, GA and had them run a smoke test on it. (As an aside, owner Alan Kidson and Jerry the Porsche mechanic are top shelf guys.) Good news is NO VAC LEAKS. Left the smoke machine on for quite a while and nada.

Once vac leaks were ruled out, Jerry adjusted the WUR and bingo -- perfect idle!

In summary, doing the tune-up was a piece of the puzzle (new cap, rotor, plugs, plug wires = better spark) and the WUR adjustment was the final piece.

Woohoo! Now I'm on to other projects on the car! :D

Glad to hear.........
 

Tirwin,

It must have been a great relief to get your car running again. Did you ever try to check your control pressure? Even without running the engine, you would know if the cold control pressure was within spec. I will make a bet that your mechanic found out that the cold control pressure was too HIGH and made the necessary correction. Keep us posted.

Tony

Tony,

Control pressure was checked and it was well within spec. Don't recall the exact number off hand but it is in my notes.

From your previous post........
 

tirwin,

You mentioned in your previous post that the mechanic (Jerry) made adjustment in the WUR (????). Then it must have been off spec? Listening to your first video when you were trying to attempt to start the engine multiple times, it seemed that you were depressing the accelerator pedal to help the engine run. Was that the case? So what work was done to your car? Keep us posted. Thanks.

Tony

Tony,

What I'm saying is that the control pressures were not out of spec, but that doesn't mean they were optimal either. It was running too lean on cold start so the adjustment that was made was to richen the mixture a little. Since one of the purposes of the WUR is to enrich the mixture on cold start, it seems to me that it wasn't enriching the mixture enough.

Like I said, the biggest difference in behavior came after the tune-up. In a previous post I gave a pretty thorough explanation of what work I did, so I'm not going to belabor that here. But my belief is that the tune-up meant better spark, which meant better fuel burn.

I also had the shop re-time the engine because I did not want to start making any adjustments until I knew for certain I did not have any vac leaks. Otherwise whatever tuning was done would just be covering up another potential problem. So, no one thing was the ultimate fix, but a combination.

In the first video I cranked the engine four times. On cranks 1 & 2 I did not depress the accelerator. On crank 3, I depressed it just enough to catch it from initial stall but not enough to sustain it. On crank 4, I depressed it and tried to keep the RPMs above 2k. It looks like I was "goosing" the pedal but I wasn't -- I was trying to keep a constant and even pressure on the pedal. As you can see, there was a significant lag in the throttle response (and a hair difference in just enough and too little). You obviously can't see it in the video but when you see the RPMs surge I had actually depressed the pedal around 1-2 seconds prior.

The moral of the story is that my experience affirms what many people have said on this forum -- this is more of a tuning problem than a parts-swapping problem. I can see how it would be very easy to just start changing parameters like AFR, timing, idle, WUR, etc and get yourself in a real mess. My advice for others who have this issue is to start with the basics and work through everything methodically.

Please report back in October, I'm keenly interested to find out if the problem is still solved when the temps drop.

I've definitely noticed a "sweet spot" with mine, below it and above it she's grumbly at first. Wondering if you have just tuned right now for current (hot as 7 hells) conditions. This is not derogatory, thrilled for you it's solved, it's a curiosity on my part.