'82 SC 1st start warm-up sequence

[wgirardot]

I wanted to check to see if this is normal. On 1st start of the day ( regardless if ambient temp is cold or warm ) my idle races to 2,000 rpm and stays there until the engine oil comes to temp ( see attached pictures ) then comes down to a very stable 900-1,000 rpm and all is good. Obviously when the weather is warmer this time is shorter and less annoying than on colder days. On colder days it takes forever. Is this just the nature of the beast? WUR and AAR are tested functional and both are receiving their proper voltage

Bill

[Funracer]

Normal - almost. I would consider that a bit high for the initial idle but other opinions may differ.

A few things to check before you start moving adjustment screws. Have you done a smoke test for air leaks? I know you said idle returns to 950 but someone may have used the idle adjust screw to reduce off of a higher number. How many turn CW until the idle screw closes completely?

I have an 83SC so you and I both have an O2 sensor. Sounds like maybe its not kicking in to lean the mixture or its a taking a real long time to heat up enough to provide information to the lambda computer. Either would indicate a change of O2 sensor.

If you know how to measure FV output (lots of info on here) easy to check but a quick and dirty is to wait until the car gets to warm idle 950 then unplug the O2 sensor (left side engine compartment forward of the CDI box) if idle changes the sensor is at least doing something. If no idle change then I would replace the sensor or at least remove and test it.

Lastly you said WUR is tested and functional. What pressures are you getting for cold and warm control pressure? How long does it take to get to WCP? What is your mixture (CO or AFM or FV) setting?

[wgirardot]

Thanks Funracer. I will report back once the weather allows me to test a few things you suggested. If memory serves me correct, I'd have 1/2 to 1 full turn to close the idle adjustment screw from where it is now.


Bill

[Funracer]

Originally Posted by wgirardot

Thanks Funracer. I will report back once the weather allows me to test a few things you suggested. If memory serves me correct, I'd have 1/2 to 1 full turn to close the idle adjustment screw from where it is now.


Bill

You don’t say much about the cars history. Have you owned it for a long time? What work has been done to it lately that may have affected the idle? Last time injector O rings replaced, valves adjusted etc etc. Distributor advance should be 5 BTDC

When I bought my car in 2019 the idle screw was 1/2 turn from closed and it still idled at 1200 when warm. When everything is tight and mixture set to spec these cars are supposed to be in the neighborhood of 2 turns CCW from closed.

After replacing many seals and gaskets and cracks etc my idle screw is now between 1 and 2 turns, depending on mixture. So a smoke test for leaks might be a good place to start.

Good luck let us know what you find.

[wgirardot]

I dropped the engine and did a top end re-build last year. Every cis component was tested and all seals, orings, gaskets, boots, airbox sealed etc. I think I may have an air leak related to brake booster hose in the engine bay, but will have to wait for warmer weather to crawl into it. In thinking back, this problem existed before my re-build and seemed to manifest itself after I backdated my heat ( might have compromised a brake booster hose/fitting in the process ). Will report back

Bill

[Funracer]

Sounds like you are about where I am knowledge wise. Be interested to hear what you find so I can check mine too!

Neil

[wgirardot]

Thx, Neil


This is my 2nd '82 SC, and it definitely runs like a top, but racing at 2,000 rpm until up to oil temp has got to be annoying for my neighbors................need to fix, and will report back the solution ( might be a while due to weather ).

Bill

[boyt911sc]

Originally Posted by wgirardot

Thx, Neil


This is my 2nd '82 SC, and it definitely runs like a top, but racing at 2,000 rpm until up to oil temp has got to be annoying for my neighbors................need to fix, and will report back the solution ( might be a while due to weather ).

Bill

Bill,

Test your AAR. I bet your AAR is out of calibration.

Tony

[creaturecat]

mine?
settles down nicely in about 1-1.5 minutes. never sees 2000 rpm. maybe 1400 - for about 20 seconds. - drops down to 900, in a gentle fashion.

[Classic 911]

Originally Posted by boyt911sc

Bill,

Test your AAR. I bet your AAR is out of calibration.

Tony

In addition the AAR’s rotating valve could also be worn and letting through too much air even if the AAR is correctly calibrated.

[wgirardot]

Ok, I might be on to something: I did a smoke test on a cold engine and found a sole leak directly centered under the airbox. It possibly may be a leak that somewhat seals itself up ( but not completely ) when oil/engine come up to temp. Car is definitely driveable and extremely healthy until I can pull the cis and test/fix sometime in the future. What I might try is to pack some fiberglass batting into the area to see if this reduces my warm-up idle somewhat until I can drop the motor and properly fix. Words of wisdom to anyone that has their motor out: check and test all hoses, fittings, and airbox rigorously and independently of each other 1 by 1

Bill

[Funracer]

Originally Posted by wgirardot

found a sole leak directly centered under the airbox.

The airbox is glued together top and bottom halves. One of the seams is directly under the center of the airbox. May be able to see it with a mirror. Look at them for sale on eBay to get an idea. This is exactly where mine split when the airbox cracked under previous ownership. Hope thats not it because you will have to pull the airbox to repair or replace.

Good luck

[wgirardot]

Pretty sure I narrowed it down to a leaking hose between the aar and airbox. Will have to drop the engine when the opportunity allows. Anyone have a picture of this connection when your engine was out; this is one of the pictures I failed to take during my refresh?

Bill