Need More CIS Help, Please
 

Many of you patiently followed and commented on my thread of last summer/fall regarding the hard starting/warm running problems my car was having. Pressure tests showed that my WUR wasn't rising above cold levels, and that when I used a substitute w/ a correct warm setting, the engine would pop the popoff valve every few seconds@ idle.

In order for the engine to run smoothly when warm, the wcp had to be about 2.4 bar, or about 1 bar lower than spec. Cold starting @ 15C needed a ccp of .8 bar, also about 1 below spec.

Three mechanics, all w/ CIS experience, and I found no vac leaks. We put in new plugs, changed the points, rotor and cap, and wires. A new MSD CDI and coil were installed.

When I was in San Francisco (beautiful!) last October I had someone rebuild and recalibrate the WUR to the "new" specs. I reinstalled the WUR and ran it only about 3 wk until last year's early winter set in.

Now it's spring. Unfortunately things still are not right. The engine starts and stays running w/ a steady 1300 rpm idle from cold @ 0 to 5C on the third key turn. Driving during the warming up stage produces a bucking, and a choked off feeling, w/ an unwillingness to rev past 3000 under load. To me this feels like the mix is too rich.

As engine temps rise the engine revs more freely and the bucking goes away. Letting off the throttle produces a short rev pause, then a gradual descent to about 1000 w/o dipping below. The engine will idle there for a few seconds, and then sort of hiccup, the revs will suddenly drop, and then they will come back up. This repeats about every 5 seconds until it stalls, or I rev the engine. This is also similar to a too rich symptom, but it isn't a rhythmic, "sine curve" type of thing. It feels more like a miss.

Once the engine reaches 190, the revs sometimes stabilize, and other times go through that miss-type scenario. At this temp, quickly getting off the throttle produces popping. The popping seems to be a combination of tailpipe and popoff valve, but I'm not sure.

Turning the idle screw doesn't change the idle speed. Leaning the mixture seemed to help get rid of some of the popping, but then another 1/8 turn leaner netted more off throttle popping.

The tailpipe is very black.

All of this suggests a too rich mixture to me, maybe from the control pressures now being too low. But they were arrived at from last fall's tests which produced intake backfiring when the cps were @ spec.

One mech commented that my dizzy reached full advance @ 2000 rpm, which is lower than normal, but there didn't seem to be anything broken, so we are thinking that was part of the mod done to the engine back years ago.

I haven't checked the cps on the car. Whitney was out of stock of the gauge. Is it possible the cps are different (lower) on my car from the way they were set up @ the rebuilder?

I'll be glad to hear from anyone w/ ideas on this.

Paul,

My experience is that the fuel and control pressures have to be correct for a CIS system to run properly. Are you sure you're not compensating for another problem with the unusual CP setting? This is just a wild guess, but could problems with the fuel distributor or injectors be an issue?

Scott,

Yes, it's possible, although one mech checked fuel flow, patterns and delivery and pronounced them fine. Also, we speculated vac leaks, but none were found.

Also, nothing else was changed on the car between when the tests were done and the rebuilt WUR refitted. That's why I'm thinking the rebuilt WUR either wasn't reset to the spec I provided, or the WUR performs differently on the engine from the way it does on the bench.

I think I may have to get a gauge on it and check.

Tomorrow I think I'll try plugging the decel valve line and then the vac retard line and see what happens. The dizzy has no vac advance.

CIS troubleshooting........
 

Paul,

Go back to the basic CIS troubleshooting. Don't do anything until you have checked your fuel pressures (cold and warm). J.C. Whitney has the CIS pressure gauge kit last week in their inventory. A friend received his order too.

Secondly, not being able to locate any vacuum leak in your engine does not mean you don't have an existing air or vac leak. There are so many places where air could leak in a CIS including the backside of the engine. So to eliminate any guessing, simply test the system by doing a simple pressure test. If the pressure gauge remains steady or unchanged for 15 mins or longer, you could safely declare the system has a good vacuum or no air leak. Keep us posted.

Tony

Thanks again, Tony.

I think I may be able to borrow both a pressure gauge and an AF meter. I'll check both cps and see if they differ from last fall's findings and/or the factory spec. I'll also be able to tell if the mixture is really too rich, or do I just think it is.

What pressure test are you referring to? I did the one to check residual pressure for the fuel accumulator and it was well above the 10 and 30 minute specs. Could you explain what you mean?

Vacuum and air leak test........
 

Paul,

IMHO, the two (2) most critical factors in CIS are fuel pressures and air mixtures. The other requirements for combustion like compression and ignition are another separate discussions. As you often suggested: 'check fuel pressures', 'check air mixture', 'check for air leak', etc.

Many have suggested the use of carb cleaner, propane gas, etc. in search of vacuum or air leak in a running engine. But what if the engine does not run at all? How do you check for vacuum? BTW, spraying flamable liquid on a hot running engine is not considered a prudent and safe practice. And I expect some will rebuke this statement. Safety practice is another separate topic.

I'm not an expert by any means, but I come to like CIS troubleshooting. So to simplify troubleshooting, I apply about 10 to 15 psi. (compressed air) into the sealed CIS system and observe the pressure gauge reading. A vacuum apparatus could also be used for this test. It is a lot easier to locate an air leak than a vacuum leak. Keep us posted.

Tony

Get the gauge and check pressures. How did you change the pressures as noted in 1st post? I change the length of the pin in the wur, but this is a finicky process, and it seems that you made really big changes.

Check other stuff, warmup air valve may be weird if your idle does not respond to changes in air bleed adjustment.

There are really only a few degrees of freedom in this system, but many things can badly affect how they respond. If you have checked obvious vac leaks, you should be good to chase other issues.

I once thought I was chasing a fuel problem when I actually had a wire grounding against the stupid braiding on the plug wires.

I'll bet the airbox is cracked.

what car, the 77 or the 80?

All good thoughts there.

Kodioneill,

The chassis is a 77 w/ an 80 engine enlarged to 3.2 w/o lambda and using a points dizzy.

Milt,

Not out of the question. I'll still look for leaks.

914efi,

The AAR, AAV and decel valve are certainly prime candidates for air leaks. The decel seems to be working because the revs hang up before dropping. The AAR seems to be working because from cold the revs initially stay high and gradually fall to spec idle speed. The AAV is suspect since the car takes a few tries to start from cold, so the sensor plate may not be raising @ cold start.

After trying various pressures during tests last fall, my mech and I both came to the conclusion that 3.4 or so warm created a too lean condition, and that about 2.4 warm was required. I had someone clean and reset the large plug to get 2.4 warm. I don't think they shortened the pin. The small plug was set to get .9 @ 15C.

I hear you. Standard practice is to always check ignition first when troubleshooting supposed CIS issues. Strange thing happened yesterday: after adjusting the mix, the engine initially didn't want to start. First time for that. No sound, no crank; nothing. Then it fired right up and was OK from then on. I smelled a faint "burned" type smell from near the coil and dizzy. It's possible it was a short as you had. Checked all wiring visually and all seems OK.

Tony,

You have to spell it out for a DF like me. I guess I need a Schraeder valve or similar installed somewhere. Where would be best? Then apply an air hose to it while the fuel pressure gauge is in place and watch the reading for 15 min or so?

hey paul,
when mine would buck, low rpm in high gear, richening it up made it run smoother, not to say it would not buck if too rich.
i can drive it down to 2k in 5th and accelerate smoothly.

here is my thought on the warm 2.4 CP. if the CP is too low, the plate will be in the wrong section of the venturi in the AFM. IE, the plate will be at a much higher angle thus putting it in the mid RPM section when the car is idleing. as you know, at around 1500 RPM or so, the mixture starts to lean out for the mid RPM running.
with the 2.4 CP, you may not be leaning out in the mid RPM making it buck and run bad because the plate is already past the place where it leans out and now in a linear mid band section. you may start running rich early for the high RPM range. my mixture starts to richen at 4k, but my WUR is different than yours.

another thought is the frequency valve. if you have one, and dont have the computer, what effect does the FV have? with no O2, does the computer hold the FV open? does it hold a 50% duty cycle? or is it closed? with no computer, is the FV open,closed or what?

could there be something wrong with the FD itself? as you know i just found a bad injector line. my car idled and drove fine up to 4200, then nothing.

my AFR at idle is about 13.5, above 1500 it drops to the low 15's, you could be running your idle mixture at all RPM's due to the low CP.

if i had your motor, i would look for a euro CIS or one from a 78-79.

tony I'm curious to, how are you pressurizing the intake system, sounds like a good idea, how do you keep from loosing press, from an open valve?

paul, are you still using the 02 f/d? and f/valve? if so, how did you disable the 02, by pulling the relay or just unplugging the 02 sensor, if you pulled the relay, are you using an earlier vacuum controlled wur? seems you or tony one had a novel about wur, i cant remember which one

I have not owned a CIS car in some years now but if I recall correctly they have a cold start valve that injects extra fuel in cold weather. Could this valve be leaking or stuck somewhat open? Once warm I'd pinch off the hose that feeds this valve and see if it has any effect on idle.

Just a thought.

Thanks for the comments, guys.

Part of the difficulty in setting up this engine is the fact that I don't have an O2 sensor, frequency valve or computer.

I am using a vacuum controlled 78/79 WUR. Last fall, using a pressure gauge I "determined" that the stock 3.4 or so warm cp produced a too lean mix. 2.4 seemed to be what was required to work. My rebuilt WUR has been set to 2.4, but it as obvious to me that it is too low, producing a too rich mix during warmup and when warm. After 20 yrs w/ this car I can judge mixture pretty well by how the engine revs and reacts.

What I don't know is why, when 2.4 seemed right last fall in tests, it appears to be too low now. It may not have been set correctly when rebuilt, or maybe my engine has different vacuum from the bench, resulting in an even lower wcp. I agree w/ Ty that the new CP is causing my current symptoms. I am pretty confident if I get the warm cp back up to where it should be per spec, I'll be good.

My next step, thanks to Mark 87930's loan of a pressure gauge, is to check what my pressures actually are, now that the WUR is in the car, and knock the plugs as required to see how it works.

I won't be able to do this for another couple of days. In the meantime I'm going to try psalt's suggestion to plug my vacuum retard line (I have no vac advance) and see if that smooths out the idle and helps starting.

I'll also continue to look for vacuum leaks.

Sal, the CSV was checked by a mech last fall and pronounced good, but I'll try the piching off test. Thanks.

Don, all that stuff was taken out by a rebuilder for a PO of the engine almost 20 yrs ago. The WUR is a vac controlled one.

Paul,

You seem to indicate the car runs rich, if this is the case I don't think the trouble would be a air leak or cracked intake as this type of failure would result in lean mixtures. It is possible you have a air leak but I do not think this is the route cause of your issues.

How rich is it running? Do you know what the warm idle CO or AFR is?

Also, the very best way to test for Air Leaks is with a Smoke Machine many pro tuner shops have these. I had mine tested for $40.00 locally, well worth the money. You will find even the smallest leaks with this method, I was amazed it even showed smoke around the throttle plate shaft!

Paul,

In my opinion, if you have a lambda FD and air flow sensor and you are not running the FV, you have a mismatch of parts that may never be able to produce the fuel curve need for all operating conditions on a road car. The lambda CIS FD is calibrated with a default FV pulse, and this controls the mixture in a different way than the WUR. The mixture with a disabled FV is leaner at all points on the curve and compensating by reducing control pressure alters the basic relationship of the sensor plate to the air flow sensor funnel shape. I have seen this done on track cars that are tuned pig rich and run at zero or WOT, but perfect cold start, warmup and cruise at different temps may be expecting too much.

Hey Paul,
Are you still running a 'brand X' {audi or something} WUR? One of the interesting things on the 78/79 CIS is the thermo valve and vacuum port on the WUR. The valve blocks vacuum from the WUR and allows the engine to run rich during the first few seconds of start up. Once it opens it allows the WUR to lean things out a bit until the bimetal strip heats ups. Just wondering what WUR you are using..or should be using.

I agree completely. You need to be 100% sure there are no vacuum leaks before you move forward. This is not a typical niggling CIS issue, there is something fundamentally wrong that several mechanics have not been able to solve.

Thought..sounds to me like the distributor is not accelerating properly or returning to TDC with the idle down.
If its not responding, soak in a vat ofWD40 with the pod removed, blow it out and lube it.
Reinstall the pod
Bruce

Do a preassure test from distributer to wur and run the car with preassure guage on also make sure the line from distributer to wur is perfectly clear if it is even a little clogged it can make a huge problem.

Usually, the vac pod is not the problem but the inside advance mechanism is.
To clean the bearing for the advance plate, the distributor has to come apart and the center bearing has to be freed up with penetrading oil NOT WD-40.
The same for the top half of the shaft which is part of the mechanical advance.
The weights and springs on the bottom have dirt and goo that needs to come out.
WD-40 is not a penetrating oil!
After cleaning, lube the parts; they have to move freely.

with CR you have you want to be as rich as you can get it. keeping my retard connected allowed me to richen the mixture at idle up a 1/2 a point or more which equals richer at WOT.

this goes back to what i was saying earlier. you may be better off finding a non O2 CIS. i saw 2 very nice systems for 3-500 a few weeks ago. i would have bought one for my 3.0 but i did not have the money. i am going to put my 2.7 CIS on the 3.0 because of the unknowns of the FV and no computer.

some of the 930 guys are removing the FV with what seems to be good results, but that is a different FD.

did you say you have acess to something to check AFR?

psalt,

I hear you. Remember, though, I've had this same system on the car for about 17 years. It appears to be from a 79, which of course was non lambda. It's only recently that I've had problems. I don't doubt that a fully equipped system would work best under all conditions--that's what it was engineered for. I agree that "perfect" may be out of the question, but the whole thing ran great for years until recently.

Ty,

See above. This is the same setup I'd had for years. I originally had a 79 911 WUR, swapped in an Audi one, and have now gone back to a rebuilt 79 911 one, albeit possibly set w/ cps too low. The same Pelican who is loaning me his pressure gauge will loan me his LM-1 at a later date so I can verify CO then. I think I'll wait on disconnecting the vac retard until I confirm cps.

Re distributor:

2 mechs looked it over separately and said it looked fine, w/ the exception of it reaching full advance early. Both felt that this was part of the engine mod done years ago and not a recent malfunction.

The LM-1 results will be very helpful, we need to know what the AFR is at idle then also under load.

Hi Paul,

I can ship you my spare WUR and you can test with that, that may at least remove some guessing. It is from a 944 but you can get the CP numbers from a web search, it's pretty close and my 78 3.0 ran fine on it. I swapped it out to the correct one numbere 045 (with vac richment) for my car and it didn't make much of a diference, recurving the dist and advancing timing did more.

Cliff,

That's very kind of you. I don't think I'll need it, but I'll let you know. The WUR I have should be perfectly fine, except set for CPs too low, based on my findings of last fall. As long as it's working correctly, I should be able to eventually set it to the CPs the engine needs. The WUR was rebuilt in October by some pros near you (Livermore). BTW I was in the SF area then and loved it.

Sal,

As soon as I can get my hands on the LM-1, I'll give it a try and post results. Based on "butt dyno" it's too rich @ anything beyond startup, but I'd like to know for sure.

If it is indeed to rich we need to think here, what could cause over rich condition?

- I doubt an air leak
- I suspect bad WUR causing to much fuel delivery
- Bad injector(s)? somehow no longer regulating fuel correctly. Take them out and stick them all into a bottle/can, spark the fuel pump up and lift the CIS air plate, how do they look are all 6 spray patterns the same?
- What else could cause extra fuel into the system?

True, but the bucking he described sounded like lean to me...

thats what i thought too. mine bucks when it is too lean. never tested at too rich.

paul,
i thought this back when you said all is well. your CP is too low causing the AFM to incorrectly meter the air due to the plate never dropping gown into the idle area of the AFM. your CP needs to be around 3.4? and your vacuum needs to connected to a port below the throttle plate. mine is connected at the rear of the TB at the bottom. is the vacuum connected now giving you the 2.4 bar or is that without vac? i dont remember, did you put a new WUR on? or was it used.
i am sorry to keep harping on this, but you cant stray too far from what porsche did with CIS. even though your motor is not stock, get the CIS back to stock configuration and go from there. otherwise there will always be a question about is this causing a problem. the CIS system just monitors how much air your motor asks for and provides fuel for that given amount of air.
i dont remember if the 79 had the thermo time valve, but that device will allow your WUR to operate from .8bar cold up to 3.6 hot. the stock WUR will not properly operate in that range without the help of the TTV. my CP's go from .8 cold to 3.6 warm.


i just connected the LM2 yesterday. 13.1 at idle and 14.8 at 3k. a bit on the rich side. AFR at WOT was about 12. maybe in the upper 11's.
when i removed the retard and reset the idle, the mixture was 12.8.

I know you have a lot on your plate and many tests yet to run but here are a few more thoughts to add to your list.

1) I agree with the advice that you should set the the control pressures set per the factory specs using a known good WUR valve. That valve sounds supect to me.

2) Vacuum leaks are more difficult to find then you can imagine. The best test for leaks these days is done by a "smoke machine" It produces a minor amount of smoke with UV dyes attached to each molecule. It uses pressurized nitrogen gas to flow the smoke into the air box, intake manifold and every hose and device connected to your air box. It is performed on the motor when it is not running. It is best to remove the air filter and its housing and then seal up the rectangular air filter housing opening with a piece of sheet metal cut to the right dimensions and then duct taped over the opening to seal off the hole. After the gas has filled the intake system, you then use a portable black light to look for leaks. The Smoke machine is quite expensive ($2k to 3K) so it is best to find a dealer or repair shop that will do this test for you. Find someone who is well experienced with using the device. Sounds complicated but it really isn't and it can be done fairly quickly once that air cleaner opening is sealed up. There is a lot of peace of mind that comes from knowing you absolutely have no vacuum.

3) I had a warm running problem with my 1976 911S motor and tried changing many (too many) components on the CIS. It eventually turned out to be a slowly failing Bosch CDI box. I ran a secondary ignition voltage test and was very surprised to find a voltage of only 6 KV instead of 40 KV! I had previously thought that the CDI was OK as long as you could hear the box squeal when the power was on. This is not always true. Would you believe this motor still started easily and idled well and ran well when the motor was cold but hesitated and skipped under acceleration. I wasted a lot of time and money on that one.

4) Is the control piston inside the fuel distributor head moving freely? With the fuel head removed from the motor, the piston should slide down freely with just gravity pulling the piston down. The dimensional tolerances on this piston are very tight and they don't take kindly to any dirt or residue buildup on the piston or the bore. This is an easy test to do. Clean things up with a little carb cleaner and a lint free cloth while it is apart. After my motor sat in storage for a winter, the piston was stuck and actually had to be pushed out with compressed air. After cleaning the parts it ran well again for many more years. This CIS system does'/t like to sit in storage, not being run.
Lyle

Porsche_Monkey and Ty,

You are right that too lean can cause surging. The reasons I "know" it's too rich in this instance is because the tailpipe is extremely black, I know how the engine feels when too rich, and as I lean the mix via the screw the bucking goes away. Also, the wcp supposedly has been set to 2.4 bar, which, as Ty said, should be giving me a too rich mix. My tests will involve knocking the large plug down, which will raise the WCP. I am hoping as it approaches 3.4, the rich symptoms will disappear.

Last fall, when reinstalled the WUR I set the idle mix to 13.2 AFR, which is about 3.5% and then left it for the winter. It's only this spring that I'm really able to go after it.

Ty,

@ what ambient temp is your ccp .8 bar?

Sal,

You most likely haven't seen my thread from last fall. I think it is too rich simply because the WUR wcp has been set too low when rebuilt. The injectors were tested last fall.

Lyle,

The CDI box and coil were replaced during the hunt for the cause of this problem. When I get the thing running, I'll have a smoke test. I'm pretty sure the plunger is operating freely. As I mentioned earlier, when I leaned the mix, the engine revved beautifully. I'm thinking it's just a mismatch between the CPs and the sensor plate. The @ rest position of the plate is where it should be BTW.

Gunter,

The diz looks good. BTW I "owe" you some info from a post last fall. When I can I'll get back to you.

i dont remember the temp. im in the south so not as cold as you are. my brother has the pressure gage so i cant go do another check for you. maybe this weekend. i would be curious if the cold CP was that different at 30* vs 60*.

my thought on the low is CP is this. you can set the CP almost anywhere and with the mixture screw, make the car run and/or idle good. but you lose proper mixture across all RPM's. i was looking in the bosch CIS book earlier, yes im at work, it breaks the AFM into 3 sections. 1 for idle, one for part throttle and one for WOT. the reason for the CP tolerance, IE 3.2-3.6, is to make sure the plate is in the correct section of the AFM for the operating needs for the motor.
i am sure the LM will be a good help in your case.

i am sure you are too rich. if what i am sying is correct, you set the idle mixture at 13.2, and because of the low CP, you are not leaning out in the mid RPM's and you are staying in the 13.? range making it run, but not as good as it should, and with the rich mixture, your upper RPM's are probaly fine. how bad do the plugs look? take a run at about 3K for a few miles, if you can, kill it before you idle and pull a plug or 2. if you can take it on the hiway, put some HW miles on it then check them.

i looked at my plate one time at idle, i think it was open about a 1/2 inch, had to use a mirror and i just did a quick glance.

i have an LM2 maybe we can work something out if you need it. 4 of us went in and bought it, maybe if you buy the tach adapter ill send it up there if the others are ok with it. the LM2 has the record feature, but you really need the tach info to be of good use.

did you buy a new WUR last year?

I agree w/ what you are saying re the AF settings vs the sensor plate height vs the CO setting vs the CPs vs the rpm range. I think you've summed it up well. It seems to me I just have to get them back into sync.

The reason I asked about the cold cp temp is, as you said, our temps get lower here. I use the car down to about 25F some years. Also, as I'm sure you know, the chart only goes down to 10C (about 50F) where, for an 80 engine, the ccp is 1.5 to 2 bar.

Does Bosch consider this to be the lowest cold cp range, or can we assume that the cold cps go down further, say to between .9 and 1.4 @ 0C?

I'll check my sensor plate height @ idle once I get a smooth idle(!) and let you know.

I haven't checked the plugs, but since the tailpipe is black I'm sure they are too. Remember, I've owned this car for 20 yrs.

AFA the LM--thank you, but for now, I think I'll be good once Mark 87930 is done w/ it.

I didn't buy a new WUR. I took my old 79 one, which I had swapped out for the Audi one for a couple years, had someone in CA refurb it when I was visiting there, and reset it to (lower than spec) CPs that I thought were going to be right for the engine, but which seem now to be too low.

One missing piece to the puzzle is why did the car run well last year with such a low CP? This has me disturbed, a CP of 2.5 just seems to low but if it ran well last year like this it means somehow the air meter must have not been metering all the air because if it had been metering all the air the air flap would have been opened far more than it should have with such a low CP. Are you sure you did nothing else to the car?

Am I making sense here?

Yes you are, and I'm wondering the same. I'm thinking that I was just being too optimistic then. The temps were lower then by about 10C (which is quite a bit ) than they were when I tested the car last Sat, and I was able to test it for a short time only. So I'm thinking (and hoping) that I was seeing its performance under different conditions, eg colder, denser air, lower engine temps, etc.

The thing that I'm more unsure about is why I got the lower numbers required in my earlier tests, the ones that led me to have the WUR reset. Maybe this is what you are referring to. Then I was using a WUR that wasn't operating correctly and setting it to different points and observing. I'm also thinking it's possible the settings either are wrong, or the amount of engine vacuum I have is different from the one used on the bench, or I just got it wrong.

Unfortunately I can't do my testing until Thursday, but I think I'll know then.

If you are sure, that's fine, but a black tailpipe is not the same as black smoke. Unless you clean your tailpipe regularly.

you have an 80 engine but 79 CIS.? i would use the CP for the 79 CIS and WUR.

as far as temp goes. notice the charts give W CP with and without vac, but the cold is always with vac. so if you take into consideration the 1bar drop due to the TTV (if your car has one) that puts your CCP in the .5 to 1bar range. i think porsche added the TTV in 77 to drop the cCP to .8 to fix the blown air box problems and dropped the TTV when they added the O2. i have always just figured once the temp got down to a certain range the CP would level off but at .8 bar(on mine) it was low enough for 50F or 20F so i never really took the temp into consideration. i can get the presure gages this weekend but may not check until sunday or monday. now the low temp at night is only about 60F, i guess i will have to get funky and figure a way to drop the temp to see what it does to the CP.

I'm shooting for the 79 spec. I'll know in a couple of days how that works.

Low temps overnight in the 60s! Sigh...I can only dream...

Don't worry about retesting your ccp on my account, unless you wanted to anyway. Sounds like you'd have to drive it into a cooler to get the temp dpwn!

Supposedly mine is set @ something like .8 right now, so about the same as yours. You may be right, that the ccp sort of levels off. I've started another thread asking about this, but so far no other responses.