Engines Stalls on light throttle, in gear

[Charlie_es_cool]

As the title says, my car (1975 dart sport w/ 318 and 904) stalls under light throttle in gear. If I drop it in drive and lightly press the gas pedal, it stalls. If I mash it momentarily, it pulls. But as soon as I let go the throttle, the engine dies. I can rev the engine in park or neutral without issue. My car had stalled under light throttle a few days ago, but I was able to get the car moving again under light throttle so I didn't think much about it. But now I can't even move it out of my driveway.

Other thing that's weird, I noticed the idle was off when I started it this afternoon. It felt rougher than Sunday (previous time I started and drove the car). I advanced my ignition 3 degrees to get a total of 36 (I didn't do this to "fix" my idle issues though, I had been wanting to do this to see how the car ran) After this, I re-adjusted the idle mixture screws on my carb. And now my car wants to run rich!! I find this odd, because previously I always adjusted them 1 1/2 turns out, and smoothest idle and vacuumm was achieved by turning them in a few 1/4 turns. But today, I had to turn them out further than the initial 1 1/2 turns. If I turn them in a 1/4 turn, the car wants to stall.

After doing this with the carb, I backed out of my driveway and drove the car for a few minutes. During my short ride, I tried to launch the car. Dropped it in drive, stepped on the brakes and revved the engine. But.... it stalled. Tried again and the same. I was able to get the car moving again by mashing the throttle and no brakes, and under WOT there were no sign of hesitation or stalling. I overshot my driveway so I had to turn around. And again, the car stalled turning around. I was able to get it going by stepping on the gas after starting it, but when I let go of the gas it stalled. Coasted it into my drive way and tried retarding the ignition to the way it was, but the problem persists.

Any help in troubleshooting this would be greatly appreciated.

 

[Dave 74 Dart]

I'm just a rookie but sounds like what my son's car was doing when we found a carb bolt was stripped on the aluminum intake. Major vacuum leak. Check around carb and intake.

 

[oldkimmer]

Yes, check for vacuum leaks first. Then fuel filter and pump. Tighten all clamps. If the pump is sucking air along with fuel u will have a stumble, hesitation or stalling. Kim

 

[AJ/FormS]

As the title says, my car (1975 dart sport w/ 318 and 904) stalls under light throttle in gear. If I drop it in drive and lightly press the gas pedal, it stalls.If I mash it momentarily, it pulls. But as soon as I let go the throttle, the engine dies. I can rev the engine in park or neutral without issue. My car had stalled under light throttle a few days ago, but I was able to get the car moving again under light throttle so I didn't think much about it. But now I can't even move it out of my driveway.

I think this is an easy fix; see note 5
but first this;
Your low speed system consists of; the fuel-level,the transfer slots, the IDLE mixture trimmers, the various air bleeds see note 4, and the IDLE-TIMING.
Now;
Assuming everything is in order ; see note#1
>the idle quality is set up by balancing the T-slots with the mixture screws. and
>The idle-speed is then set with timing.
See how easy that is?

Here's what you don't do;
You don't set the Idle-Timing to some non-factory number, that you think your engine might want, or need: it will never be enough.This will make setting the idle tip-in as good as impossible.
And you don't set the Idle-Timing by vacuum.

Here's what you do do:
using the curb-idle screw;
you balance the T-slot position, to the mixture screws, that have been previously set to, in the middle of their adjustment range, about 2 turns on a Carter; to eliminate the tip-in stumble. This is job-#1.
Then,with Idle-Timing, you set the idle speed to whatever; doesn't bang into gear, nor stall going from Neutral to in-gear.

To help you baseline this, here is a starter-tune;
set the timing to 5*BTDC,
set the mixture screws to, in the center of their range, about 2 turns out,on a Carter.
Set the idle speed to 550 in gear, with a fully warmed up engine.
That is your baseline, now if you have a tip-in stumble, return to the top

Note1
Assuming
The compression is decent and even, and
the wet fuel level is correct,(note3) and
the Vcan is plumbed to the SPARKPORT,the PCV is working correctly,the air-bleeds are clean(see note 4), and that ALL other systems are working as designed;

Note 2
if you have a 4bbl. make sure the secondaries are closed up tight, but not sticking; BOTH sides the same.

Note 3
You have to know about pull-over.
When you set the fuel level on a Carter, the end result is to get the running wet fuel-level to a design height that the designer has determined will get the job done. The wet level then, is the important thing. This determines how high up in the fuel wells, the liquid is.
The higher it is, the easier it will be for the fuel to be pulled up and over the top, into the transfer/idle discharge ports. Pull-over,get it?, lil.
Conversely, if the running fuel-level in the bowls is too low, then it will be difficult for the fuel to be pulled over, and then you get hard hot-starts and poor idle quality. So every tune starts with verifying the fuel level is according to the design, and that it remains there at all times.
And, nothing works if the bowl is not vented, or if the tank is not vented.

Note 4
If you suspect dirty air bleeds, you have two options;
1) remove the mixture screws, and blow the circuit out. You have to use low pressure and short bursts so you can't damage anything.
2) with the engine running at a high idle(1800rpm or so), you slam the choke shut, and release it before the engine stalls. This brings manifold vacuum to the underside of the choke, and the idea is that the vacuum there will suck the dirt out.

Note 5
But I could be wrong, if the timing chain has jumped.

Happy tuning

 

[MOPAROFFICIAL]

Pump shot, plunger.
Or you can adjust the rods to come out sooner to enrichen earlier.

 

[Dartfreak75]

Accelerator pump? Maybe? I know they will make one stall under heavy acceleration.