Idle problems triple webers on l24

[Tyler]

I'm reposting this in here in of getting some more responses.

 

Something odd is happening with the idle. So when I start it up, I have to play with the gas for about 3 minutes until the temperature probe moves on the dash, then if I let go of the gas it'll stumble low to about 400 rpm and die.

 

On the other hand, if I pop the hood and manually give the throttle a little "blip" it'll go to about 850 rpm and idle great.

So I thought maybe I have to just give it a tap or two of the gas pedal to recreate the same thing. NO! It doesn't work. If I then proceed to pop the hood and "blip" it again it'll idle fine.

 

Also after some time driving trying to figure this out, the idle still draws to a stall and will have a hard time regulating the idle unless I manually press the throttle lever on the carbs.

 

 

-Idle at 850 rpm. It drops to about 650-700 rpm with lights, fan, and radio on.

-Idle screw down 3/32 of a turn past touching

-Mixture screws set to 1 1/4 turn out all the way across

For reference the carbs are:

45 DCOE

36mm choke

155 Main Jets

170 Corrector Jets

55 F8 Idle Jets

F16 Emulsion tubes

 

On my previous tune last where I microtuned with the ColorTune Tool for the mixture I got for the turns out

#1- 1 1/4

#2- 1/1/4

#3- 3/4

#4- 1/1/4

#5- 3/4

#6- 3/4

 

Please HELP!

 

 

Thanks

 

Tyler

[crazyoctopus]

kinda sounds like an issue i was having with my triples for a bit, but i am not running chokes. and since you are in california you really shouldn'a have to either.

 

have you synced your carbs air flow with a synchrometer? not a unisyn, but a synchrometer liek this one... http://www.thezstore.com/page/TZS/PROD/TE/60-9976

 

if you have, neat.

 

the reason why the engine would give you decent idle when you blip the throttle with your hand may be due to some sticky carb return springs. are you running individual return springs for each throttle arm? I personally have to run 2, on carbs 2 and 3 to make sure that that all of the carbs are returning to dead stop on the throttle return set screws. one way to check to see if they are sticking is to blip the throttle by hand and then push the linkages up to make sure they are seated completely, if the idle drops the linkages need to be adjusted/cleaned.

 

fuel mixture is secondary to making sure that the air entering your engine is equalized, once that is done then you can work on fuel.

 

 

 

 

 

 

[Tyler]

kinda sounds like an issue i was having with my triples for a bit, but i am not running chokes. and since you are in california you really shouldn'a have to either.

 

have you synced your carbs air flow with a synchrometer? not a unisyn, but a synchrometer liek this one... http://www.thezstore.com/page/TZS/PROD/TE/60-9976

 

if you have, neat.

 

the reason why the engine would give you decent idle when you blip the throttle with your hand may be due to some sticky carb return springs. are you running individual return springs for each throttle arm? I personally have to run 2, on carbs 2 and 3 to make sure that that all of the carbs are returning to dead stop on the throttle return set screws. one way to check to see if they are sticking is to blip the throttle by hand and then push the linkages up to make sure they are seated completely, if the idle drops the linkages need to be adjusted/cleaned.

 

fuel mixture is secondary to making sure that the air entering your engine is equalized, once that is done then you can work on fuel.

 

I do have a synchrometer and I am having issues synching each carb. I can synch the ones direectly connected to the throttle linkage, but not the ones without. I think I may have to run them like you. Come to think of it, I have tried blipping the throttle by hand and pushing back and it feels like there is the slightest little give.

Should I try something like a carb cleaner and see if it'll clean up any gunk?

 

By the way, any pics of your carbs? I'd like to see how you have your linkage setup.

 

Thanks a million!

[crazyoctopus]

if the same carb is gives you vastly different air values there is a leak in that carb.

 

http://www.redlineweber.com/html/Tech/dcoe_adjustment_layout_typical_i.htm is a good place to start looking when tuning your carbs.

 

 

 

 

and btw double posting is a no-no

[yetterben]

Chokes are the inner diameter sleeve inserted before the aux venturi. Webers don't have chokes like a normal CHOKE. They have cold starting devices. Which is what you are not running.

[crazyoctopus]

yeah yeah... guess I should have been a bit more clear...

[cygnusx1]

 Those carbs are HUGE if you are running a stock 240Z motor.  That can lead to transition difficulties as the air velocity in the chokes is very slow.  As far as your idle problem goes.  It sounds to me that your linkage is binding and/or the carbs are out of synch.  You also want to make sure that the butterfly's are blocking all the progression ports at idle so that all of your idle mixture is passing through the idle mixture volume screws.  Do your carbs have air-bypass screws?  If so, you want to close them off to get the tuning right.  Oh, and tuning a dirty weber is like pissing in the ocean.  Clean those suckers up if they are getting a bit old. 

Edited April 23, 2010 by cygnusx1

[Tyler]

Thanks for the input, all. I'll be checking out everything you've said.

Sorry about double posting, I was getting a bit worried seeing as how I daily drive it for work and needed to be up and running by 6 a.m.

[bjhines]

You can pull the caps off the transition port openings and visually look to see where the throttle plates sit at idle. If you have one or more of the plates opened too far then idle can become erratic. Transition slots/holes need to be completely closed off at idle. Idle should not be set by your throttle plate set screws. Those are not there to "Sync" the carbys. There are usually bypass screws to do that job. Your idle air bleeds may be too small or your carby has some partially clogged passages.

[Tyler]

I cleaned the carbs with cleaner and reset the linkages. Seems to have helped some bit. A good amount of "brown" came out of them. No it'll hold idle fine, but I still get inconsistent idle rpm readings. At first it'll sit nicely at 700 rpm, but after driving it'll idle at 1000-1100. And then when I get into traffic it'll get back down to around 700-900 rpm.

 

Maybe I need to clean them some more.

[19762802+2]

The tachs in Z's aren't always accurate so that may be something to think about also.

[crazyoctopus]

next time it sticks at 1k blip the trottle and see if it returns to the 700.

 

mine does the same thing (650 to 900) but I am sure that it is just a linkage issue, yours may be the same thing.

[Konish]

I had the same problems with my DCOE 40s...they don't shut all the way to the stops (sometimes...say 7 out of 10 times) unless I blip the throttle. I have observed that the throttles will want to "fall" open when the motor is running and have a harder time returning to the fully closed position.

 

When the motor is off or the carbs are off the manifold, the plates snap shut positively without delay. I know there are "experts" that will absolutely state that the Webers have *no* problems closing while the engine is running, but I have observed this phenomena on 2 personal sets (DCOE 40, 45 152s..the 40s were rebuilt and the 152s are brand new), and several videos that exhibit the same exact behavior.

 

I have high quality heim joint linkages and billet AL link arms and there is no binding in any of my control linkages.

 

Anyway, back to your problem. You say when you pop the hood and the blip the throttle by hand, it's all good, but if the hood is closed it acts strange? I may have missed this but have you tried to pop the hood when you see the idle stumbling and then try to blip it with the pedal (i.e. not getting out of the car to blip it my hand)? Have you had a friend help you open the hood all the way and then blip the throttle with the pedal?

 

One final thing you can check which was totally giving me fits. The throttle shaft off the pedal goes through the firewall through a grommet and there is an adjustment nut on it. The nut on mine had backed itself really far back on the shaft which caused it to catch the edge of the throttle shaft exit hole. The nut was causing the shaft to hang both while opening and closing the throttle, which was hard to diagnose with the pedal. Also, the Rube Goldberg linkage was binding a bit as well, making things even more sloppy.

[bjhines]

Triple linkages are tough to get right. You can get all your idle openings perfect and then bugger the adjustment on the linkages at the carbys.

 

Another issue I noticed is that heat soak will tend to result in increased RPMs at idle. They don't like hot air at all.

 

You should smoke-test the intake to be absolutely sure you have no leaks while the engine is hot.

 

If you have properly set up your linkages and you have no vac-leaks, then your problem is worn out throttle shafts.