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Designer King
 
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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.
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Yellow 77 Sunroof Coupe/cork interior; 3.2L '80 SC engine/10.5:1/No O2; Carrera Tensioners; 11 Blade Fan; Turbo tie rod ends; Bilstein HDs; 28 tube Cooler; SSI, Dansk; MSD/Blaster; 16x7" Fuchs/205/50 Goodrich G Force Sport Comp 2; PCA/UCR, MID9
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Old 03-28-2009, 01:41 PM
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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?
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Old 03-28-2009, 01:47 PM
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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.
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Yellow 77 Sunroof Coupe/cork interior; 3.2L '80 SC engine/10.5:1/No O2; Carrera Tensioners; 11 Blade Fan; Turbo tie rod ends; Bilstein HDs; 28 tube Cooler; SSI, Dansk; MSD/Blaster; 16x7" Fuchs/205/50 Goodrich G Force Sport Comp 2; PCA/UCR, MID9
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Last edited by Paulporsche; 03-28-2009 at 03:15 PM..
Old 03-28-2009, 03:10 PM
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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
Old 03-28-2009, 05:16 PM
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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?
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Yellow 77 Sunroof Coupe/cork interior; 3.2L '80 SC engine/10.5:1/No O2; Carrera Tensioners; 11 Blade Fan; Turbo tie rod ends; Bilstein HDs; 28 tube Cooler; SSI, Dansk; MSD/Blaster; 16x7" Fuchs/205/50 Goodrich G Force Sport Comp 2; PCA/UCR, MID9
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Old 03-28-2009, 07:37 PM
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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
Old 03-28-2009, 09:29 PM
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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.
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Old 03-29-2009, 06:07 AM
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I'll bet the airbox is cracked.
Old 03-29-2009, 06:17 AM
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what car, the 77 or the 80?
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Old 03-29-2009, 06:58 AM
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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?
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Old 03-29-2009, 08:27 AM
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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.
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Old 03-30-2009, 04:41 AM
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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?
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Old 03-30-2009, 04:57 AM
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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
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fully disassembled, blasted, customized and restored 75 targa with factory hard top, 993 style turbo ft fenders, steel flares, C2 bumpers and rockers, 82 3.0 sc 9.5/1 engine with PMS flywheel, 964 cams, flowed heads, ssi's short geared 915 w/lsd, polybronze, bilstein,working lambda, modified and highly tuned cis, tensioners, pop valve, backdated exhaust and heater, 2300 lbs. no bolt left untouched. 1970 911E. Nice car but needs a re-do.
Old 03-30-2009, 05:06 AM
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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.
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Old 03-30-2009, 05:36 AM
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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.
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Old 03-30-2009, 05:48 AM
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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.
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Old 03-30-2009, 05:50 AM
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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!
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Last edited by scarceller; 03-30-2009 at 06:04 AM..
Old 03-30-2009, 06:00 AM
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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.
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Old 03-30-2009, 06:09 AM
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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.
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Old 03-30-2009, 06:10 AM
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Quote:
Originally Posted by scarceller View Post
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!
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.
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Old 03-30-2009, 06:11 AM
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