Idle too low with A/C On

[boulky12]

My idle with A/C Off is 700 rpms in Park and 500 in Drive.

My idle with A/C On is about 650 rpms in Park and about 450 in Drive.

I've been stalling lately sometimes when I put the truck in gear, A/C On and try to take off. And i think its because my rpms are too low.

I've tried adjusting the A/C solenoid on the Carb all the way until it touches the throttle bracket. That didn't help much. Is that even the correct way to adjust it?

If I wanted to bump up the idle on the Carb, would the proper way to do it be with the engine warmed up, In gear, A/C on? And its the idle speed screw on the driver's side correct?

Carb is a Quadrajet

Thanks

[bd]

My idle with A/C On is about 650 rpms in Park and about 450 in Drive.

I've tried adjusting the A/C solenoid on the Carb all the way until it touches the throttle bracket. That didn't help much.

Is the idle solenoid even energizing?  The solenoid's plunger should extend and hold the throttle open whenever the A/C is turned ON.  If you're saying that you adjusted the plunger out to touch the throttle lever while the solenoid was de-energized, the engine will idle dangerously high if and when the solenoid actually energizes - possibly fast enough for the vehicle to get away from you!  With the idle solenoid's plunger fully extended, engine RPM should be adjusted to about 550 RPM in drive.

Use a test light to check for power at the idle solenoid with the A/C running.  If there's power to the solenoid and the plunger isn't extending, replace the solenoid.  If the circuit is dead but the A/C works, there's an open in the green wire running between the solenoid and the low pressure cycling switch at the accumulator.  If the A/C compressor doesn't energize either, then there is a bigger problem - check the fuses.

[boulky12]

My idle with A/C On is about 650 rpms in Park and about 450 in Drive.

I've tried adjusting the A/C solenoid on the Carb all the way until it touches the throttle bracket. That didn't help much.

Is the idle solenoid even energizing?  The solenoid's plunger should extend and hold the throttle open whenever the A/C is turned ON.  If you're saying that you adjusted the plunger out to touch the throttle lever while the solenoid was de-energized, the engine will idle dangerously high if and when the solenoid actually energizes - possibly fast enough for the vehicle to get away from you!  With the idle solenoid's plunger fully extended, engine RPM should be adjusted to about 550 RPM in drive.

Use a test light to check for power at the idle solenoid with the A/C running.  If there's power to the solenoid and the plunger isn't extending, replace the solenoid.  If the circuit is dead but the A/C works, there's an open in the green wire running between the solenoid and the low pressure cycling switch at the accumulator.  If the A/C compressor doesn't energize either, then there is a bigger problem - check the fuses.

Solenoid is energizing. Test light lit right up. And compressor is energizing of course cause I got cold A/C.

Found out the solenoid actually goes in effect after you press the accelerator pedal once. Rpm's shot right up like you said.

So I started goin back down on the solenoid plunger. Took me several times of turning it off and adjusting it but I eventually got it @ 550 rpm in Drive. Feels a lot better now. Cant wait to go drive her.

Thanks bd

[Stewart G Griffin]

So, i'm wondering in general that if you shut an engine off with the AC still on, will the engine tend to diesel on?

[bd]

"Dieseling" or "run on" occurs when too much air enters an engine.  Any mechanical problem such as sticky choke linkage, a vacuum leak, an improperly adjusted base idle screw, grossly misadjusted idle solenoid, or worn throttle shaft bore that holds the throttle plates open or bypasses the throttle entirely can result in run on.  A properly functioning idle solenoid retracts when power is removed, dropping the throttle linkage to the base idle setting.  As long as said mechanical problems do not exist, run on (dieseling) should not occur.

[Stewart G Griffin]

"Dieseling" or "run on" occurs when too much air enters an engine.  Any mechanical problem such as sticky choke linkage, a vacuum leak, an improperly adjusted base idle screw, grossly misadjusted idle solenoid, or worn throttle shaft bore that holds the throttle plates open or bypasses the throttle entirely can result in run on.  A properly functioning idle solenoid retracts when power is removed, dropping the throttle linkage to the base idle setting.  As long as said mechanical problems do not exist, run on (dieseling) should not occur.

OK, gotcha.  Thanks.