I just rebuilt my CCC Quadrajet on my 1984 98, and now it's idling Extremely fast. (I don't have an RPM gauge or tool) The engine runs amazing, no shakes or stutters, but the second it gets put into Neutral or park, it revs up and idles really high. I've gone through everything I can think of. Messed with both idle screws but they haven't changed anything,(All screws except for those are in factory positions. I don't see or hear any vacuum leaks, and all parts on the carb seem to be running how they should. I assume the Dieseling is caused by the high idle as well, but the car has sat since 94, so I know there's carbon build up stuck in there.

Any help woukd be greatly appreciated, thank you.

 

Is the choke blade opening completely when it is warm?

 

Yes, when the car is warmed up the flaps fully open

 

You won't be able to tune your CCC Quadrajet without a factory service manual and tach/dwell meter. I think @joe_padavano posted CCC tuning pages in the past. Hopefully he contributes to the thread soon.

 

Check that the high idle cam on the right side of the carb between the choke thermostat housing and the carb mid-section is dropping down to the lowest step when the choke blade is fully open.

 

The only way to adjust the idle mixture screws is using either a scan tool or a dwellmeter to read the duty cycle of the mixture control solenoid. The idle speed can be affected by three things - the fast idle screw on the choke linkage, the curb idle screw, or the Idle Load Compensator. If you don't have a factory Chassis Service Manual, get one. The computer-controlled carb on these cars MUST be adjusted following the factory procedure exactly.

 

So it turns out the secondary throttle flaps on the bottom of the carb were not on just right
they were stuck open

 

Glad you found the problem.
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