81 911sc CIS lambda MIA

[marty911sc]

I'm starting this thread to document a typical problem.
No cold start(without a spritz of start fluid)
Idle hunts until warmup.
Runs like a sewing machine.
though this post is premature ,I sta
The car was meticulously maintained. One owner.
I have a stack of receipts totaling over 20k.
All the upgrades have been completed.

This post is probably premature because I need to check out a lot things.

I looked under the passenger recaro seat and there is no ECU. exhaust backdated. No O2 bung.

I talked with the previously mechanic, he stated its the mixture setting.
I did just order a CO sniffer. The control pressure is within range.
I do not know if the frequency valve is installed.
like I said premature....

Pressure is within range. Plugs have a beautiful perfect toast color.

[tirwin]

What year is the engine supposed to be? I mean, do you know the engine has been modified or changed out? I think the 81 has the ECU under the pass seat, so if it's not there, we need to know why. Is it US or RoW?

[schumicat]

the frequency valve is controlled by the ecu. the FV makes a distinctive buzzing sound you can hear if you stand behind car with decklid open w/ engine running. the FV adjusts the air fuel ratio and is important. car will run like crap until warmed up w/o it and will be lean under heavy load.

[boyt911sc]

Marty,

If your 80/81 SC is a RoW or Euro car, there will be no ECU. The FV might be there but not utilized. Could you check the WUR part number? Pictures of the engine would help too. Thanks.

Tony

[James Brown]

can you post the VIN and the engine model # (like 930/16)

[Bob Kontak]

Originally Posted by James Brown

can you post the VIN and the engine model # (like 930/16)

Or 930/10

[James Brown]

or 911/72

[marty911sc]

My bad. I think I have it straight now. And it was good. Very good.
I own a 1980 911sc RoW. No ECU. If the simons 911 website is correct.( I mixed up my MY cars and that site states MY80 has lambda.I edited my first post)
Vin 91A013, All original Grey market, oh ya!
I was told , second hand, it was ordered from Germany, which I didn't take much stock in. I had the car in storage for over a year, and just got it to the house. I was also told it was setup for regular pump gas. I'll think that means the lower 91 octane, so it is not at the RoW HP rating. I'm going to tend to believe this now.
I thought I needed zzz in the Vin,but this is only 81 later 17 digit?
I could be just a mixture adjustment.
Feeling Good..
Being an prior airplane wrench, this seems right up my alley.

[Bob Kontak]

Good for you.

If it were messed with to become federalized you know they did not take out the pistons. Do some research on numbers - WUR/Fuel dist/ign dist and find out what was change and post what you find. Folks here can help you get it back to where it was meant to be.

[boyt911sc]

Originally Posted by marty911sc

My bad. I think I have it straight now. And it was good. Very good.
I own a 1980 911sc RoW. No ECU. If the simons 911 website is correct.( I mixed up my MY cars and that site states MY80 has lambda.I edited my first post)
Vin 91A013, All original Grey market, oh ya!
I was told , second hand, it was ordered from Germany, which I didn't take much stock in. I had the car in storage for over a year, and just got it to the house. I was also told it was setup for regular pump gas. I'll think that means the lower 91 octane, so it is not at the RoW HP rating. I'm going to tend to believe this now.
I thought I needed zzz in the Vin,but this is only 81 later 17 digit?
I could be just a mixture adjustment.
Feeling Good..
Being an prior airplane wrench, this seems right up my alley.

Marty,

Before you start tinkering the fuel mixture setting, think twice!!!!!!! This is where most of the problems start when people alter this setting. This is the last thing you want to do and would need to verify the integrity of the vacuum system first. This is a mandatory procedure and I can not put more emphasis on this procedure.

Tony

[marty911sc]

Roger Wilco,
No fiddlin' with the mixture.

Let's try this again. Doh!
80 911sc RoW VIN 91A013. Can't enough off that.

Symptom: No cold start, intermmitant at best.
idle hunt until operating temp.
No others apparent.
Step 1: Fix induction leak.
a Oil cap test
b Air box /POV. Shop Vac Pressure.
c. ?

Side note: ID WUR /fuel dist/ign
Fab up a smoker.
I have extensive records for induction reapair. The injector seals were changed several times since 1998. It looks like ever major service included them.

[timmy2]

Buy or borrow a Bosch CIS fuel pressure test kit and a Bently manual and test your system, cold and warm running pressures. Post the results and then start looking for other problems if they are all in spec.

[marty911sc]

Update,
I have been driving the car a bit. I was able to check mixture by bumping the meter plate explained on a thread here.
It has similarity to adjusting the mixture on a mg su carb, when you press the button to check where the mixture is set.
I turned the mixture screw a click in both directions and it behaved correctly. I returned it to the original position.

In regards to the car intermitant hunting
If I release the accel pedal quickly , the car idle hunts until warmed up
If I gingerly let off ,and I mean slow and light. The car goes back settles to idle perfect.

[marty911sc]

Bump

[timmy2]

Just a WAG, your Decel valve function sounds questionable as it should help drop the RPM's slowly. The sudden drop may be causing the oscillation.
What are your System, cold and warm fuel pressures?
What is your CO set to?
Without the proper baseline settings checked with the proper tools you will be fiddling with it forever....

[boyt911sc]

Marty,

Could you inspect your WUR and post the ID numbers (0-438-140-xxx)? Need the last 3 digits only. Without knowing the cold and warm control fuel pressures would be a challenged to give a meaningful diagnosis.

Have you tested for air/vac leak?
Have you tested the CO level?
What's the resistance (Ohms) reading?
Could you start the engine after the first turn of the ignition switch? How many times before you get it to run? And everything OK when warm?

Keep us posted.

Tony

[marty911sc]

I'll get those numbers.
The RPM drops slow,
I am referring to the accel pedal only.
I tested the afr and it was steady at 13.8.
It's not an intermittant hunt. Slow release of pedal and it settles to smooth idle.
Has any tried the banjo fitting adaptor gauge from utcis?
It runs like a hornet when warm. Not a hiccup.
It has been starting on the first bump, even after sitting for two weeks.

[amberdfjt]

Could you check the WUR part number? Pictures of the engine would help too. Thanks.

[timmy2]

Have you looked at the plastic bushings on the plate mounted on top of the engine where the linkage is? They are known to fail. Also the ones on the transmission rod are plastic and fail as well. For that matter the accelerator pedal has bushings...
I replaced both sets on my car with the brass style available from our host. The plastic ones will work as well.
Maybe the difference between fast release and slow release of the accelerator pedal is due to some binding or poor alignment of the throttle linkage.

[marty911sc]

I'll check it.
My thinking was throttle shaft bushings( bearing/seals)being worn. Or the pivot mechanism on the meter plate, or the plate stop it malfunctioning.
Do you have a sense on how forgiving wear is?
There is no record of these being serviced.