1981 SC CIS - low idle - wrong WUR?

[wreckah]

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...

[psalt]

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.

[82 SC]

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

[T77911S]

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

[groovydude]

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.

[wreckah]

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!

[Bob Kontak]

Originally Posted by wreckah

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.

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

[wreckah]

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...

[wreckah]

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.

[psalt]

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.

[wreckah]

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

cheers,
Jan

[Bob Kontak]

Originally Posted by wreckah

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

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?

[wreckah]

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)

[javadog]

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

[boyt911sc]

Originally Posted by wreckah

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)

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

[wreckah]

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?

[wreckah]

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?

[boyt911sc]

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

[wreckah]

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

[wreckah]

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