Engine wont idle from cold.

[r3bartl]

So, some quick back information first. this happens with my qjet and my avs2. I've changed everything but the fuel pump. I'm here in the cold white north and this happens mostly on mild days rather than cold. I have ngk spark plugs with a msd hei distributor. New wires. Performer intake with a 195 thermostat. It's a 400 sbc.

I'll start the truck in the morning and she starts up first flick. Choke activated and revs to 1500 where I set it. Shot of gas and goes right down to 1000. Engine warm up to 195 and as soon as the choke completely comes off. Falls on its face. Wont idle at 800 rpm. It's floating just above 500 and stalling out. The fuel pressure gauage I have says 6psi even when it's not idling properly. After awhile of doing that she just starts to idle probably and she's good for the day lol. She's cranky ol thing. All I have left to change is the fuel pump. Is there anything else it could be?

 

[Fastereddie]

First thing i would try is to manually close the choke flap a bit when it starts stumbling and see if it smooths out.

 

[Wes Harden]

Weak coil spring for choke.
Should spend more time on second step.
the intake may too cold for fuel to atomize, guessing the right exhaust efe valve has been eliminated or rusted open.

 

[r3bartl]

First thing i would try is to manually close the choke flap a bit when it starts stumbling and see if it smooths out.

I'll definitely give this a try.

 

[r3bartl]

Weak coil spring for choke.
Should spend more time on second step.
the intake may too cold for fuel to atomize, guessing the right exhaust efe valve has been eliminated or rusted open.

It's a brand new avs2 and my quadrajet had a brand new coil from quadrajet power. But it could very well be dialed to much to the lean side. But what I find odd is it's worse on warm days and works better on really cold. The water temp is also 180. Although I know that don't mean the intake is warm enough to atomize the gas.

And yes the exhaust valve is long sense gone lol. She has headers and aluminum intake. But she do have the cross over still.

 

[Blue85]

Is the manifold heated by coolant or is it one of those air-gap designs? What is the electric choke wired to? Have you noted any correlation between the secondaries being unlocked the idle quality?

 

[r3bartl]

Is the manifold heated by coolant or is it one of those air-gap designs? What is the electric choke wired to? Have you noted any correlation between the secondaries being unlocked the idle quality?

It's a performer edelbrock so it's warmed by coolant and has the crossover. It's wired straight to the fuse box and confirmed getting all volts and the choke opens fully. When the choke comes off the high idle cam she won't idle even with coolant temps of 180 to 195.

 

[tRustyK5]

Have you messed with the mixture screws at all yet? Once it comes off the choke that's the circuit that should be active...

On the next warmish day let it warm up as you normally do, then once you get it off the choke and with coolant temps at normal range, screw in the idle mixture screws 1/4 turn each. If the idle gets worse, screw them out. Keep adjusting for best idle.

 

[r3bartl]

Oh

Have you messed with the mixture screws at all yet? Once it comes off the choke that's the circuit that should be active...

On the next warmish day let it warm up as you normally do, then once you get it off the choke and with coolant temps at normal range, screw in the idle mixture screws 1/4 turn each. If the idle gets worse, screw them out. Keep adjusting for best idle.

Oh yes. I got it set to the highest and smoothest vacuum, 20 inches. and I got 14 degrees of initial timing. When she do finally decide to idle she's as smooth as a kitten. That's why I felt like it was the fuel pump going out. Weird for it to work right on cold days but give me issues on warm days. And once it's warmed up it's fine then for the day. This also happened on both carbs just not the new one. So which makes me think it's more of a pump problem again. Wonder if my vented gas cap is buggered lol

 

[r3bartl]

Three other things to note. When she acts like this there's no difference in neutral rpm or drive rpm. It stays constant. And also when I turn the truck off the fuel drains out of the feed line instantly. Also when she's doing this if I shut the truck off and back on it clears itself up "sometimes" and she's back to idling fine again. Lol. Cranky ol thing.

 

[tRustyK5]

Try it with the fuel cap off...report back.

 

[r3bartl]

Try it with the fuel cap off...report back.

Unfortunately the cap made no difference lol. Another mild morning here and she's becoming worse. When I got to work which is 5 mins away. She wanted to stall off throttle. She finally did stall in the parking lot. When I started it back up she ran fine. She kept surging till she finally found her idle. I set the choke to stay on longer. Turned up the curb idle up 850 900 and gave her a quarter turn more on the choke idle just to help her along. And she didn't make it down the road. The only thing I can see now is the fuel pump is going.

 

[r3bartl]

It was the fuel pump. Changed it out today and it came off choke and never stalled out. Also realized there was no bolt in the hole to hold the push rod and that's fixed my mystery oil leak I had.