1981 SC CIS - low idle - wrong WUR?
 

Hi guys,

i've got this 1981 911 Targa with some cold running issues, and i would love some input from you lot, i've done lots of research but i'm reaching a ceiling on my knowledge...

the car is mostly stock, and in pretty good condition, inside and out, original california car, so US spec. Weinrot.
I know i need to post a pic, so here goes :) :
http://www.mojomoto.be/filetransfer/IMG_9507.jpg

I just did some pressure testing and here are my results (all with non running engine, bridged the FP relay, so non vacuum):
cold control: 1.6bar (around 5 to 10°C here in Belgium at the moment)
warm control: 3.4bar (reaches after 3-4 minutes when i plug it in)
system pressure: 4.5bar
(fuel pump sound good, also no fuel leaks whatsoever)
i haven't got any residual figures because the fuel pressure tester is leaking a tiny bit in one of the connections. (i don't think it has influenced the numbers too much)

Worth mentioning: the car has no O2 sensor attached, and is running a 072 WUR,
the AAR is working good, and i did not find any vacuum leaks so far...

Issues: cold start is not great: it will start relatively easily, but never reaches high rpm...it idles (barely) at 500rpm and is very temperamental the first couple of minutes. It will stall too if i give it some throttle and then let go of the throttle. After a while, stumbles go away, and the car feels quite good once warmed up. Warm idle is rock steady at 950rpm.

It seems that warm and cold control pressures are a bit on the high side. Although it smells very rich, which is strange? It should be too lean when cold with these numbers, right?
I made the WUR adjustable for CCP, so that will be a reasonably easy fix, push it in a little bit and measure again. I opened it as well, and it looks brand new in there. Is it also adjustable for WCP? Is this WUR correct for this car?

I wonder why it keeps this low rpm when cold...any other things i should check?

cheers for the input,
Jan

warm starts are great by the way.
Airbox looks fine, new stock airfilter.
Stock exhaust as far as i can tell. Very quiet.

Same color as my '79 Targa! I had a lot of CIS adventures this past summer. My car also has the "wrong" WUR, a Euro on a California car, but with proper setup it works fine.

There are some differences between '79 and '81, but I believe the issue could also arise from the Auxiliary Air Regulator. It allows more air when cold, and slowly closes as the engine heats up. If it is sticking closed, the engine will be choked on air while cold.

In the end, there are a lot of "knobs" to turn for a CIS system. It isn't too hard to take off the top of the system (throttle body and tubes) and clean them out, and put back on. You don't have to alter the settings of anything to do this, and you can clean out lots of gunk and possibly find vacuum leaks.

911 CIS Primer - Introduction is a great resource for such things.

thanks guys, the AAR works well, so i ruled that one out. it's nicely open when cold and closes after ca. 5 minutes.

hmm...it looks like i have a 1980 WUR in my 1981. so do i go for the 072 pressures? Then i need a little bit more CCP, which means leaner running when cold...? warm is not far off then...

Year model System Pressure Cold pressure Warm pressure Vac conn Info Source

'80 .072 4.5 to 5.2 1.8 @ 10 3.5 @ 40 None F.M.

'81 - 83* .089 4.5 to 5.2 1.2 @10 3.0 @ 40 3.6 @ 40 S.B.

Jan

Is this a USA car with a cat and disconnected O2sensor , or a ROW car ? On USA models, the cold start, stumble and stalling is usually caused by a combination of the vacuum retard. a lean mixture and sometimes the wrong spark plugs. If your distributor has two vacuum lines, disconnect and plug the rear grey hose and reset the idle speed to 950 rpm with the thumb screw on the throttle body. Ignition timing should be 5 degrees BTDC with both hoses disconnected and plugged. The engine was calibrated with BOSCH Normal spark plugs and others can cause this symptom. Retest the cold start overnight. If it still stumbles and stalls, look for vacuum leaks at the injector sleeves and Orings and around the airbox with an unlit propane torch. Almost all 911SCs at this age will have leaks at the injector sleeves that will alter idle mixture due to the method Porsche choice to mount the injectors. Fix the leaks before resetting the mixture and you can usually tune these cars to instantly fire and immediately run at a 1500 rpm fast idle regardless of temperature. There is a lot about this problem in the archives.

Hi Paul,

thanks for your insights,
it's a US car, with 02 sensor deleted...edit: cat is still there.

Will try your suggestions in the morning, i will let you know what happens.
Will check spark plugs as well,

cheers, Jan

Jan,

The O2 sensor is irrelevant to cold starting, however CIS lambda requires a pulsing FV for the mixture to be anywhere near correct. You need to confirm the dome light fuse is OK, the lambda relay is OK and the FV is buzzing. If you reconnect the 02 sensor, this engine will talk to you though the test port and a dwell meter. Much better info than web posts. Search for CIS Lambda.

Pretty sure the US 81 uses the 090 WUR. Don't know if there is a California variant.

Believe the 089 is the WUR for the non-US versions through the early 80's. Perhaps the whole run of ROW SC's?

Here is the 090 chart. Your readings actually look pretty good.

http://forums.pelicanparts.com/uploa...1449098242.jpg

While you pressure readings look good for a 090, I had the exact same symptoms, and they were fully cured by replacing the WUR (with a rebuilt one from CIS Flowtech). Not sure what could be going on. Is it possible that the fuel line from the WUR to the FD is clogged?

Btw, I like your bumper/valence, do you know who makes it? Nice color too.

CIS compatible components.......
 

Wreckah,

WUR-089 is for Euro/RoW and vacuum assisted. You can not use this WUR-089 without modifying your CIS. Your problems are having a different WUR-072, O2 disabled, and your WCP & SP at the very low end of the range values. If your decision is to omit or by-pass the lambda, it would take some serious tinkering to get your engine to run well. First, could you post the fuel distributor ID number? I expect it to be -077 but who knows. Thanks.

Tony

Hi Tony,

yepp, it's a 077 FD.

i'll check the easier things first, and then move on to bigger things.

cheers, Jan

how was the O2 sensor deleted? was it just removed
do you still have the frequency valve and does it vibrate when engine is running.

mixture is way off when cold. the CCP is not far off enough to make a difference based on a stock car, but depending on the O2 sensore delete mods it could be

when cold, lift up and pull down on the aif flow sensor plate behind the air filter, just to see if it needs to be richer or leaner.

copper plugs.

ok, took off the blue dizzy vacuum line, plugged it,

set the WUR to 1.8bar CCP, as per 072 specs,

starts ok, runs 800rpm instead of 500ish, so a bit better, but still lots of backfires through the exhaust when i give a slight bit of throttle.

sprayed lots of carb cleaner around the injectors and no change in rpm to be noticed.

gonna source a FV relay this afternoon, and maybe a mirror too, because i don't know where to feel exactly for buzzyness.

groovydude: the bumpers are RUF or RUF lookalike/style (you know, yellowbird mid-eighties). They look rather nice, not cheap.

the O2 is replaced by a plug, i haven't got a clue where to wiring went or where it's supposed to be...need to look into that. PO did this.

spark plugs are Bosch W3CC

dome light, dashboard light works, pulled the relay under the seat, no difference in running.

Keep it simple.........
 

Jan,

Do you still have the ECU (lambda brain/electronics) under the passenger (right) side? You need a good working ECU plus FV relay, OXS, and WUR-090 to get your engine to run and idle correctly. An appropriate dwell meter or an oscilloscope could verify if the ECU, relay, OXS, and FV work in tandem. FD-077 is designed to run leaner than the FD intended for Euro/RoW. WUR-090 keeps the cold idle richer and longer than WUR-089 does. As you can see, it is a balancing act of the different CIS components to achieve what Bosch designed for a particular CIS unit.

Any particular reason why you want the lambda engine to run without OXS? Are you trying to make this motor to run similarly as a Euro version? Keep us posted.

Tony

spark plugs are Bosch W3CC

Jan,

Correct spark plugs for a 81 US 911SC are WR5DC.

If you pulled the OXS relay on a hot running engine with no change, you have found the problem, now determine if it is just the relay, ECU or FV. Search for Lambda CIS and you will find everything you need on this site. If the FV is not operating, chances are the PO used other bodges and posh wannbe hairdresser techniques to make it almost run properly.

Good post, I bought my 82 with the cat and 02 sensor missing. I have a bit of idle issues as in high idle but I think its mostly vac issues. Still wonder how my car is set up without cat and sensor. Pulls great thru 1 and 2nd, when in traffic and I give it some gas at high speeds it kind if shudders a bit. I am waiting on working on my 911 till after my shop is ready.
later

okay guys, thanks,

yes it has a big box underneath the passanger seat,
so i need to delve into that, this is where my knowledge stops...dwell, etc...never heard of it, need to study!

Tony: the previous owner did all this stuff, i'm just here to make it run great again, as i love the car very much (much more than my former 69T) and it feels very healthy outisde of this cold running issue. If i have to get an O2 sensor for it, then i'll gladly do this,
..to get an 090 WUR will be another story i'm afraid...

Still wonder how my car is set up without cat and sensor.

The first thing to understand about CIS lambda is that the O2 sensor is irrelevant to cold starting and throttle above 35%. Next is that the O2 sensor, the switches , and the cat can be broken or missing, but the ECU and FV must be functioning at the default duty cycle to get anywhere near the correct fuel curve. Unfortunately, the "limp home" mode is way too lean. Think of it this way, it is a Basic CIS system that is calibrated way to lean, with an EFI injector (FV) that is pulsed by the ECU to get near the correct mixture. When the engine gets hot, the ECU uses the O2 sensor information to trim the mixture back to stoich for the life of the cat and the engine, by altering the FV pulse. The reason modern engines last so long is mainly properly fueling. Choosing to disconnect the O2 sensor is like choosing to smoke cigarettes to improve your health. It has no effect on performance other than to shorten the life of the engine.

I heard without the sensor connector it runs rich? My tail pipe looks like it is on the rich side of things.

W3 is waaay too cold. that plug would go in a 930 or hi comp engine.

I visited John Walker in Seattle for a CO adjustment, and he suggested unplugging the O2 sensor on my '82. It runs a bit smoother without, although the mileage may be a tad lower, so it's probably running a tad richer overall. Still way more efficient than carbs, of course. And pre-1980 or so our cars were built with the same CIS minus the lambda. So I think that having no O2 sensor is not causing your problems.

I think the relay could be an issue for you though, and it's a cheap and quick fix. Mine was shot when I got my car, but my symptoms were also present when the car was warm.

okay, we're trucking along,

6 new correct plugs (hernia job!) and new FV relay, and result: starts much easier, no touching of the throttle, sounds much better, smoother, stinks less, but the cold idle (well, it's warming up here during daytime ofcourse, so maybe 12-13°C) is hunting a bit now, relatively slowly and smoothly though, between 800 and 1200rpm, so something deffo is better now.

no chance to go out and drive tonight, will try tomorrow, gonna try to pull the FV relay while warm and see what happens,

cheers for now guys!

New plugs. New FV relay. Is there a chance you can put the old relay in for the first start tomorrow to see how it starts with just the new plugs and report.

Put the new relay in after a quick check of old. Let it warm up and pull that relay to assess idle change.

Just a data point. I have posted this youtube vid many times. I pull the relay and it runs but it is bogging and coughing. Note the little backfires near the end of the video. It will still rev but it's not happy like before.

https://www.youtube.com/watch?v=5tdpCYyvqSc

5°C this morning,

both with new and old FV relay, perfect start, positive idle around 1000rpm, immediately good throttle response. after 10 seconds slight hunting starts to happen 900-1100rpm.
Only changes are:
- good type spark plugs
- removed dizzy vacuum retard
- set up CCP WUR to 1.8bar (072 spec)

will drive it properly later today, and see what the FV does...

alright guys,

went for a drive this morning, i immediately noticed a lot more torque down low, seriously, 30% more or so...no more waiting for 4000rpm to get going, now it's 2k rpm in 2nd gear and i can almost break the tires loose by stomping on it...

idle after a couple of minutes way high, 1800 rpm or so, dialed that down with the idle screw, still hunting idle around 950rpm when fully warm. Gave it half a turn leaner on the mixture screw and now rocksteady 950rpm. great throttle response.

warm engine: pulled out the new FV relay and the engine goes down to around 700rpm and sounds rougher (and smells rich)...but the new relay back in, and perfect idle again. Old relay in = 700rpm and rough sounding, so i know now 100% that this one was bad.

result :)
now let's wait for the next cold start and see how it she reacts.

thanks for your input guys, really appreciated!
Jan

PS i'm also going to hunt for an 02 sensor and see where the wiring went. i'll update this thread when i found something.

PS i'm also going to hunt for an 02 sensor

Jan,

Sounds like you are going in the right direction. The O2 sensor is a one wire BOSCH and you can fit the cheap universal model but you will need to splice the wire, It is a shielded wire because the signal is less than one volt, so you have to connect both elements. There is a lot in the archives on this, just ignore the nonsense about "air" traveling up the wire. One reason for fitting the sensor is that it will allow you to instantly see if the system is working correctly and to set the mixture with an allen wrench by hooking up a dwell meter to the test port connector behind the plastic cover on the left side of the engine compartment. My advice is to borrow an analog dwell meter from some crusty old guy over 50 that had a car with points, then buy a used one after you get it to work. Everything you need to know is in the archives. Good luck.

thanks Paul,

will do, every silent moment is filled with board reading and studying :)

soon, i will be that crusty old guy with a bunch of strange tools in the shed :D

cheers,
Jan

Great news. Nice job.

My O2 wire enters a plastic sheath just to the left of the rear shock mounting point and towards the rear of the car (standing at rear of car looking forward) The sheath leaves the engine compartment several inches to the front of the car from where the wires enter it. Dives down behind that left shock.

There is a second wire that enters this sheath as well, It's for one of the wires to the small test post that is usually stuffed under the relay box. That's the wire you plug the dwell meter into Paul speaks of.

I think I just figured out "mayo-country" Has to do with Belgian fries, right?

thanks Bob, yes we drown the things in mayo...we drown everything in mayo actually :)

I'm not there yet...cold start this morning was again not very good: very low idle, and thus stall. Have to keep the engine running with the throttle. Mind you, the engine reacts beautifully immediately, no popping, no backfires,no hesitation. After 2 minutes it runs on its own, and drives away perfectly from cold. If only i had a fast idle from cold, everything would be hunky dory.

I drove about 3 hours today, and it's like a new car: perfect reaction to the throttle, perfect idle, great power and torque (had a buddy drive my car and it feels really fast from the passenger seat), perfect oil temp, great sound...what a car!

I checked out his car too, he has a 1980 US 911 targa, and he has 072 WUR too, he still has the 02 sensor though. (and a cat delete)

My advice would be to get the WUR pressure down a hair, to 090 specs, get an O2 sensor wired in and working, then reset the fuel mixture with a gas analyzer. Some of your problems ought to go away.

JR

Check your friend's FD number......
 

Jan,

Your friend has the correct WUR-072 for his '80 SC US model. When you get a chance check his FD number too. Could you also check your WUR-072 resistance (Ohms) reading when the engine is cold? Preferably in the morning. And compare this value to your friend's WUR-072. Thanks.

Tony

only tiny update,

my buddy's 1980 SC also has the 077 FD.
so same WUR and FD between 80 and 81 US cars possible?

ok, more info,

to recap, the engine runs absolutely flawless when hot, but doesn't want to hold idle when stone cold (5°C) . (this makes starting multiple times necessary)
For about 30 seconds, i have to hold rpm's up, after that she will idle on her own...first at around 600, after couple of minutes perfect 950.

i checked the timing: (cold engine) (edit, got confused by the adjustable timing light)
- both with or without vacuum line: 8°BTDC
- at high rpm it rises perfectly to 25° BTDC and stays there

so there could be something wrong with vacuum advance at idle?

Jan,

What I don't see are the data for the WUR resistance (Ohms) when engine is cold and the residual fuel pressure? Could you start the cold engine without any help from the accelerator? Thanks.

Tony

Hi Tony,

the engine does fire without accelerator when cold, but dies after 1 second,
i have to catch it with the throttle to keep it going.
Mind you it would start and run when ambient temps would be closer to 20°C. Now it's 5°C.

i tried measuring the resistance but got different results with different ohmmeters...i even got an open reading as well...but the WUR heating element is definately working because CCP changes nicely into WCP...maybe the resistance is very dependant of ambient temps...? maybe the secondary heating element in there has got something to do with it? i'll try to get some thrustworthy results in the morning.

haven't been able to measure residual fuel pressure because of mini leak in the coupler of the fuel measurement kit, but i doubt there is anything wrong with that because warm starts are perfect, also after sitting for half an hour or 1 hour.

i tried adjusting WUR cold control pressure both richer and leaner, but i got no improvements in cold starting.

It won't idle by itself for 30 secs, but i do have the feeling that the mixture is almost spot on...no popping, farting, no hesitating, no vibrating...

cheers for thinking along!
Jan

gratuitous shot of my former 69 T...it was a beauty.

https://scontent-ams3-1.xx.fbcdn.net..._2389096_o.jpg