Quadrajet help needed

[87National]

I've got a couple of problems with my 86 442:
1. If I let the car sit for more than 4 hours, I need to pump the throttle a couple of times for it to start. Not a big deal but would like to understand what is going on.
2. After a cold start, the idle begins at around 1300 rpm, then within seconds, increases to over 2000 rpm. Drops down to 800 rpm if I stab the throttle.

Thanks in advance.

 

[olds307 and 403]

Sounds like your plugs in the bowls are leaking down. There is a screw facing the firewall on the pass side on the carb base plate that adjusts fast idle. Turn it counter clockwise to lower your fast idle.

 

[Clone TIE Pilot]

Some needle valve seat designs allow gas to empty out of the carb back down the fuel line.

 

[DoubleV]

The second issue might be caused by an excess of fuel in the intake that leaked in there ( a result of your first issue ). The car starts up and idle is high ( which it's supposed to be ) but since it's way over rich the engine doesn't run as good until the excess of fuel in the intake clears out. Once the excess fuel clears, the idle gets stronger and goes up to where it should be. This is just a theory I pulled out of my *ss.

 

[Bonnewagon]

Here's my edumacted guesses. You're in SD, so it's usually chilly weather and even 4 hours cools down the engine so it's a cold start most times. 1- accelerator pump is worn, so not much of a pump shot. With engine off, remove air cleaner, choke open, look down throat while pumping throttle by hand. You should see a good strong pump shot from 2 places just under the choke flap. A weak dribbly flow means the pump diaphragm is leaking. My question is- does it also need lots of pumping when totally cold, or just after running/shut down/4 hours? 2- choke fast idle is set at 2000 rpm, but choke flap is slow to open (choke pull-off is weak/slow/sticky) so it is initially too rich and all it will allow is 1300 rpm. When it finally opens fully, the engine assumes the 2000 rpm setting. 1500-2000 is a good fast idle range by the way. As the engine warms up and choke relaxes, hitting the gas pedal drops the rpm down to the 800 rpm curb idle, which is normal. Here is the operation.

 

[87National]

I adjusted the fast idle. At start it idles at 1100rpm and creeps up to around 1400 rpm.......but much better than idling at 2000+ rpm.

Are leaky plugs something that can be repaired with the carb in place?

 

[Bonnewagon]

No, the plugs are located on the underside of the carb. Leaky plugs were a 60's thing with many over-the-counter fixes available. You won't find them for sale anymore because the Rochester plant corrected the problem around 1970 or so. Nowadays the problem is the 10% alcohol in gas which causes it too evaporate so fast you think it must be a leak.