ignition timing, how to adjust? idle L Jetronic

[Wildthings]

The spec is 20,5°-24,5° of centrifugal advance which you are adding to 7.5° of static timing for 28-32° BTDC at full mechanical advance, with the engine running cooler if the timing is limited to ~28°. By setting your timing at only 24° you are giving up some power and gas mileage.

During hot weather (>30°C) there isn't much harm in dropping your timing back to 27° (the book spec for a Type 4 car) or even 26°, but by going further retarded, your exhaust temperatures are going to climb as combustion is taking place too late and you risk damaging the exhaust valves and seats.

[Pepite73]

hello I set as you told me in advance static at 7.5degres Btdc and I added 20.5 degrees in dynamic and I arrive at 27.5 Btdc and it works very well. I am now trying to find out how to put the air circuit under pressure and look for a leak; do you have a good method?
(idle is correctly reached at 900 rpm and it sounds good)
thanks very much
I will measure the consumption

[busdaddy]

[Pepite73]

[

img]https://www.thesamba.com/vw/gallery/pix/2283009.jpg[/img]
to complete the subject, I have trouble getting an idle speed at 950 rpm but rather 1100 rpm,
I need your opinion on the following questions:
- At what temperature should I adjust the ignition advance? Cold? after riding? nothing on it. the values ​​change if I set cold or hot.
-if I get idle at 1100 over 7.5 degrees ahead, if I get 28 degrees in dynamic at 3600 rpm; can I turn the distributor until I still get 28 degrees but slightly lower the advance, like around 5 degrees, to get an idle around 9500 rpm? is it dangerous?
-I remind you that my problem is the slightly high idle, whereas I have just checked my compressions: good at 9; I have just readjusted my rocker arms (mechanical tappets), I checked with a smoke tester that there was no air leak on the depression circuit... (effective).; there is no leak on the non-return valve of the brake booster, nothing on the oil filling, etc.
the only thing I see is the flap in the throttle body which may have become slightly oval... is it possible that this is playing?
this part seems very hard to find
I checked the injector seals and everything is ok with the smoke tester(that I inserted at the level of the hose of the auxiliary air valve).


I note that I do 16 half turns backwards on the screw of the air flowmeter (richness screw) to lower the speed a little.. (the idle screw is fully tightened); a friend told me that it was necessary to base 8 half turns back on this screw of the flowmeter but I do not really see better results.
noted that I had an evaluation done on a CO measurement bench at the outlet to adjust this screw and measure the CO expressed, but the values are good over a wide range of use;

the accelerator cable is well adjusted / I just did the emptying..

in short, the combi works perfectly, on the other hand I always stay with the idle a little high..
Do you have any ideas ?

thank your very much! a friend from France

[SGKent]

Did you put a few drops of oil on the distributor wick and verify that the timing advance is working correctly?

Something is allowing too much air past the throttle body. Did you check all the diaphragms to be sure none are leaking - decel valve, canister purge, distributor can, fuel pressure regulator, brake servo?

Did you inspect the throttle body to see if it is worn out?

Did you inspect the aux air valve to make sure it is closing when the engine warms up?
_________________
"Most people don't know what they're doing, and a lot of them are really good at it." - George Carlin

[Pepite73]

yes, the advance work well and i put some oil yesterday inside.

i checked all this:(all the diaphragms to be sure none are leaking - decel valve, canister purge, distributor can, fuel pressure regulator)
i didn'it checke the brake servo... what must i verify insise?
the brake servo non-return valve is good because I checked it. after I smell gasoline when I fill up and the car moves, could there be an air leak in the fuel event circuit or on the filler neck?

i changed the diaphram of the igniter but my decel valve i don't know if it work well. i did the test and changed hoses

thank you very much

[Pepite73]

I need your opinion on the following questions:
- At what temperature should I adjust the ignition advance? Cold? after riding? nothing on it. the values ​​change if I set cold or hot.
-if I get idle at 1100 over 7.5 degrees ahead, if I get 28 degrees in dynamic at 3600 rpm; can I turn the distributor until I still get 28 degrees but slightly lower the advance, like around 5 degrees, to get an idle around 9500 rpm? is it dangerous?

what do you thibk about this?

[SGKent]

temperature doesn't matter. You cannot adjust it properly at 1100 RPM is you are trying to set it to the factory specs. At 1100 RPM the mechanical advance is already starting.
_________________
"Most people don't know what they're doing, and a lot of them are really good at it." - George Carlin

[Wildthings]

You may get a slight variation in your timing with temperature 1 or 2 degrees, but since most of your miles are going to be with the engine hot, check the timing with a hot engine.

Throttle bodies wear out and thus pass more air than they should. On the Vanagon forum there is mention of who out there rebuilds them. You could start be checking the classified.

[ToolBox]

[Pepite73]

thank you very mich withing and redhome, i will check temperature and air leaks

[Pepite73]

Hello everyone,
My Combi has a very high idle speed at 1300 RPM when stationary. I’d like to find a solution to lower the idle speed to around 950 RPM. I’ve checked everything, there’s no air leak with the smoke tester, and my distributor is properly set at -7.5 degrees BTDC. I don’t understand why the idle speed won’t come down. I’m wondering if the deceleration valve could be the issue. Any ideas?

I have 24 degrees of advance at 3400 RPM, and if I increase it to 28, the idle speed goes even higher. The spark plugs are new.
Do you think I should change the distributor? I lubricated the small plate under the electronic distributor in the distributor, and it works.
So I'm wondering if I need to find another deceleration valve, which seems impossible to find?
I replaced the air flow meter with a different one, and it gives the same result.

So I'm lost; I don't understand how to lower the engine idle speed.
(I recently changed the gearbox to an ultra-long one.)

Sincerly

[dodger tom]

knowing the year, engine type, and other details will
help the sambexperts help you out.
_________________
1978 Champaign Edition 2 Westfalia
Would never find the time to keep up another classic air-cooled.

[airschooled]

Hi and welcome,

First, make sure this is the screw you're using to adjust the idle speed. Big flat head in the middle.

Some people mix up the screws on the AFM. If you did adjust the screw on the AFM already, warm up the engine and set that screw to where the engine runs best, then go in a full turn.

Good luck,
Robbie
_________________
One-on-one tech help for your vintage Volkswagen:

www.airschooled.com

https://www.patreon.com/airschooled

[Pepite73]

Thank you Robbie,
I tightened the idle screw fully as you indicated. I loosened the screw on top, i.e., on the air flow meter, but that doesn't lower the idle speed.

Thanks for your reply, Robbie.

Pépito (Xavier)

[airschooled]

If you’re bottomed out and have zero vacuum leaks, it’s time to remove the s-boot and look at your throttle body. If it has the hole in the center like this one, it is for a DVDA distributor.

If the hole is absent, your throttle body is probably worn out.

If you do have the hole, you can solder it shut to return functionality to the file speed screw. Or, if you have two vacuum nipples on the throttle body, use a DVDA.

Robbie
_________________
One-on-one tech help for your vintage Volkswagen:

www.airschooled.com

https://www.patreon.com/airschooled

[Pepite73]

I didn't understand why you said it was worn out if it didn't have the hole?
Why?
I'll put a picture of the inside of the throttle body and the number. Thanks a lot for your help Robbie

[img]https://www.thesamba.com/vw/gallery/pix/2283009.jpg[/img

]

[Pepite73]

I noticed that this winter when it was cold my idle speed was good at 900 rpm and since it has been warmer it has gone completely haywire about 1300 t/m

[Wildthings]

Have you checked into whether your AAR (auxiliary air regulator) is closing fully once the engine warms?

Your throttle plate clearances look good to my eyes.

[Pepite73]

Yes, I clamped it and it doesn't lower the rpm. I had already changed it to new and checked.