Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

E4me ccc fast idle

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Bud:
Have a question about my fast idle since the weather has warmed up some I've noticed my fast idle is not the same as it was when I start it idle goes up but then you can hear it go down not really a stumble but you can tell it goes down then comes back up until you work the pedal the fast idle doesn't seem like it's as high as it was 1500 now around 2000 before this started today when I started instead of coming back up it went down more and stalled the car but restarted and it idled up and kicked down I have checked the choke pull off holds vacuum and adjusted the choke and checked to make sure the throttle opens have not adjusted the fast idle yet cannot figure out why it would have changed and the car run good when driving this may not even be a carb problem not sure was also thinking about the efe valve in the exhaust what's your take on this

Cliff Ruggles:
The throttle shaft position is controlled by the fast idle cam when the choke is on.  Some cams have one step, others 2, 3 or even 4. 

If it's on any particular step as it warms up it may idle at a different speed.

Engine speed will also vary some as it warms up as the choke flap opens and the intake heats up.

Doesn't rule out problems in other areas, vacuum leaks, EGR, timing, etc......Cliff

Bud:
Little hard to explain but it does this when its on the highest step of the cam so idle should stay high until you kick it down but when the idle goes up it will come back down and then go back up until you kick it down I give it one pump to set choke and fuel shot to start but yesterday when I started fast idle was high but then it went down and didn't come back up like its been doing and the car stalled but restarted and then did the high then low then back up until I kicked it down this is just something different that it hasn't been doing noticed it when the weather has warmed up as far as timing it's not been changed and runs and starts ok doesn't seem to have any vacuum leaks either the egr is not stuck and can move it with my hand also no check engine light either one thing I'm not exactually sure is working right all the time is the efe valve I can usually hear it close when I shut the car off after driving but there have been some recent time that I couldn't hear it this is a 87 Monte Carlo ss and this does seem like a sort of strange problem any way thank you for your time

Cliff Ruggles:
If it drops off the high step it should not go back up there for any reason, unless the electric choke isn't heating up like it should.

Having the RPM vary some on the high step would be normal, as the choke flap opens and intake heats up, but it should be on the high step very long.

I spent some time adjusting the electric choke on my carb and ended up using a pretty light setting since the car is mostly driven in warmer weather.  I'm just a little impatient and don't like to sit there very long waiting for it to open and idle down so I can back the car out of the shop and drive it.

It did take me quite a while to find the ideal setting for the way I use the car, but once I nailed it down choke operation is pretty much flawless. 

The only problem I have is that the intake is cold (no heat crossovers in the aftermarket aluminum heads) so it can be a little off in really cold weather and require some "heat soak" before the engine will idle well.

Something I've learned to deal with as I've been running these heads for nearly 20 years now......Cliff

Bud:
I think choke adjustment may be my problem I adjusted it so it closes shut when work throttle and when the pull off will open throttle about 1/8 inch guess I need to physically make sure it's on the highest step one thing I'm not exactly sure of is how tight the throttle needs to be when it closes guess I'll have to play with it

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