car dies at idle sometimes

[Tyler]

'72 240z- triple 45 dcoe weber carbs

 

Hi, I have a problem with my idle. When the car is warmed up and sitting and idling it holds at about 500 rpm just fine, but sometimes when I drive it and come to a stop it'll slowly stumble to about 300 rpm and then die on me. I'm not too sure that's going on.

 

Help!

 

Thanks

 

Tyler

[neotech84]

Do you have a fuel pressure gauge on it? If so can you get a reading for when it stumbles?

[Tyler]

Do you have a fuel pressure gauge on it? If so can you get a reading for when it stumbles?

 

 

I don't have one, but will soon.

 

Here's what I posted on my end results on classicz.

 

So after getting really frustrated, I just rechecked, retightened, retuned my carbs. I Pulled vacuum lines off, pushed them back on tightly and ziptied them. I redid the arms on the linkage. I retuned the idle mixture and idle. Here's what I got.

 

-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 night 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

 

The car drove wonderfully, but I could not hold an idle at stop. Maybe due to incorrect jet sizing?

 

Let's hope the idle holds fine tomorrow!

 

Tyler

[Tyler]

WEIRD THING WITH THE IDLE

 

So now 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.

 

Any ideas?

[260zkt]

WEIRD THING WITH THE IDLE

 

So now 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.

 

Any ideas?

 

I have the SAME problem, Im about to order new carbs... Im sick of it dying out.

[T-Bone028]

So if you blip the throttle from under the hood, its perfect. But from the gas pedal, it dies.

 

I would imagine that there is something going on with your linkage. Maybe binding or improper geometry of your linkage? Have someone operate the gas pedal while you watch whats going on at various throttle positions/loads. BTW, I'm just throwing out blind guesses...hope you find a fix.

[ModernS30]

You could try to open your idle screw just a touch? If you do this and then it goes up and down open it a bit more and you should be golden. Had a similar issue when I first got my car. Mine would just go up and down until I got the fusible link fix and then it would just plain die out because idle was more smooth. So I had to open the idle screw. Idles plenty fine and low. No issues since but USE LOCK TIGHT! I almost lost my screw from vibrations. Going on an hour drive and then hitting your first stop light to have your car go RRRRRRRRRRRRRRRRRRRRRRRRRR BAHHHHHHHH and stall. No fun.

[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.