Need More CIS Help, Please

[Flat6pac]

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

[nh911]

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.

[Gunter]

Originally Posted by Flat6pac

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

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.

[T77911S]

Originally Posted by psalt

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.

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?

[Paulporsche]

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.

[scarceller]

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

[Porsche Head]

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.

[Paulporsche]

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.

[scarceller]

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?

[Porsche_monkey]

Originally Posted by scarceller

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...

[T77911S]

Originally Posted by Porsche_monkey

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.

[Lyle Detwiller]

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

[Paulporsche]

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.

[T77911S]

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?

[Paulporsche]

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.

[scarceller]

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?

[Paulporsche]

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.

[Porsche_monkey]

Originally Posted by Paulporsche

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.

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

[T77911S]

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.

[Paulporsche]

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.