Im having a bit of trouble with my 81 vette. I live in jersey and the temperature has recently dropped to the 20s with wind chill on occasion, and my vette can't handle it. It's my daily driver so I kind of need it to be running and don't know what to do first. Heres what happens

- When I start it usually starts right up but sometimes it cranks for a while
- It'll idle for a while at about 800 RPM (normal) but instead of racing it'll drop to about 500 and then chug for a little, ending with a stall (Keep in mind this is without me touching any pedals and while it's still in park)

-When I pop it into reverse it almost always stalls

- When I start driving every time I give it gas it feels like it's going to stall, and if I continue to give it gas or remove my foot from the pedal it will stall. If I flutter the gas pedal however it occasionally saves it from stalling.

The idle is the same as its always been, and once i get it successfully on the highway and run it at 60 mph this usally stops from happening. I do let the car warm up for a good 10 - 15 minutes and this still happens.
It's an automatic, and we recently removed the air pump so I'm wondering if any of my vacuum lines are connected wrong, so I have some pictures.

These pictures are of when the car is warmed up. I'll try to get some pictures of when it's cold soon enough

 

I would check out the electric choke system. Once the car warms up after driving it that system isn't used. But until it does reach operating temp the choke helps richen the mixture to keep it running. As cold as it is and it is only running 800 rpms when you start it further makes me think it is in the choke system. I believe it should run between 1500 and 1200 rpms until the car reaches operation temp. I hope this helps you find the problem.

 

The pics don't show the EFE (early fuel evaporative) actuator on the passenger side. That closes off the heat riser butterfly valve in the passenger exhaust manifold on cold start-up to direct heat across the intake manifold passage to the driver's side during warm-up. It basically warms the fuel in the carb and helps the choke. It is vacuum controlled by a thermal vacuum switch (TVS) in the thermostat housing that I can see. Does the rubber line from the TVS lead to the actuator valve (small canister at bottom of pic)?

 

Well in that chambered tube that runs into the air filter in the picture, with the little rubber hose connected the valve door remains closed, but when I remove the rubber hose the door opens up, if thats what your talking about.

 

No I am speaking of the heat riser valve in the passenger exhaust manifold along with the vacuum actuator. Not the air cleaner assembly.

 

Try adjusting your fast idle and idle screws. There may be other problems but that will get you driving again. I too think its your choke as well but also could be retarded timing. Justin

 

Paul:

Yes, the hose does connect to from the TVS to the EFE on the manifold.

How would I go about fixing my electronic choke without messing up my machine driven choke?

 

I'm not sure what you mean by a machine driven choke. Post a picture of your choke assembly.

 

By machine Driven choke I mean the way the choke operates after it reaches a warm enough temperature as opposed to how it's powered when it's cold.

I'll get on getting that picture hopefully sometime today.

 

Your fast idle should be higher. You have to set it with the motor stone cold by depressing the throttle half way then releasing. Take a look to see if the cam under the throttle arm is on the highest step. If that is not the case, you have to bend a link on the choke side of the carb (at least on the old carbs). You should get a manual with details of adjusting the choke and follow the steps in order.

The next thing to check is the choke pull-off being set too far open. It works by a vacuum device and opens the choke a small amount when the motor first starts. That amount is critical and is controlled by bending the linkage. This picture shows how it should look with the motor running, is that your car? The motor is not running in that picture, the choke isn't closed all the way and needs to be adjusted.



If it is set properly, then I think your choke is coming off too soon, you should adjust it slightly towards "rich".

Chokes are complex, but worked well when new. The trick is getting them adjusted to be like new. A good manual is the key. Joe

 

Paul,
The EFE actuator is down low on the exhaust heat riser valve on that year. You can see in the first picture the white stripe hose that attaches to the EFE hard line going down to the EFE actuator. There is another rubber hose down lower at the transition from the hard line to the actuator and I bet it is leaking there. The short rubber line gets baked by the exhaust manifold and after all these years it has probably failed.

I figure there might be a vacuum leaks somewhere that is giving the idle problems. The hoses have been messed with and maybe that started the problem?

-Mark.

 

Well if it helps the car wont start at all now?

It cranks but just won't turn over.

Blah.

 

Try having the battery tested - if it is weak, it won't crank the engine well when cold.