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You will need to have the THROTTLE RETURN DASH-POT
on your (unspecified) carburetor tested and adjusted... and the IDLE SPEED correctly set.
Idle Speed and a slow rate of RPM reduction is
critical to the proper function...
Some LESSOR "mechanics" will attempt to raise the
IDLE SPEED to compensate for a malfunctioning
DASHPOT... This will PROFOUNDLY exacerbate
the problem.
you don't adjust the idle for any accessories
The idle is set for smooth running of the engine( normally 750-900 rpms with a drop of 200-300 rpms with an ac running so set the idle at the upper rpms and it will still be smooth when the ac is on without affecting gear engagement
your problem I take it is that when the ac cuts in the idle rpms drops and makes the engine run rough
This is normal as the ac compressor takes up to 5 hp to drive it
what you need is an electric controlled vacuum pot connected to the accelerator lever so that when you switch on the ac the power to the ac clutch energizes the pot and vacuum pulls the accelerator lever to maintain the set idle rpms
such an item is found on most early carby operated engines
With due apologize, the very first thing which I would like to amend is that it is not 22 k but it is 2.2 k (2200 rpm).
To solve the problem please check the following:
- Vacuum leaks. (PCV valve, A/C idle up vacuum switch and actuator, vacuum hoses routing, gasket intake manifold, distributor vacuum dash pot.
- Valve clearance.
- Ignition system.
- Carburetor vents and lines for clogged.
- Idle speed solenoid switch and its connection. (Remove the solenoid, put a finger on its hole on the carburetor, start the engine keeping the finger on the hole. If it maintains the stable rpm replace the solenoid or check the voltage on the switch).
- Adjust the air fuel mixture.
If it is conventional carburetor type check the ac dash pot for maladjustment, VSV swich or vacuum hoses. If it is EFI then service the throttle body system and idle air control valve.
Hi,
Check the a/c actuator, round metal with rod at the bottom, vacuum hose at the side. Located beside the carburetor.
When you turn on the A/C it will push the idle up( via vacuum system ). It has an adjuster at the top to set the right rpm of your engine.
Test also the vacuum hoses and A/C vacuum switch, just follow that black 1/4" dia. hose( vacuum hose ) and check the system.
If you have no idea on repairing the vacuums and the actuator, my suggestion would be to bring your car to the nearest A/C technician to have him repair it.
Thanks for asking FixYa!
Hi,
Look for the aircondition actuator, located alongside at the end of the accelerator cable. Its a rounded metal canister type, it is operated by vacuum from the intake manifold. The vacuum is controled by a solenoid valve that when you turn on your A/C it open the valve and let the vacuum sucks the actuator.
Check the actuator of its vacuum hoses that might been disconnected or already have cracks/cut off, thus vacuum leaks.
If the vacuum hoses are okay, you have to adjust the shaft in the actuator, it pushes your idling up, the shaft has an adjustable nut and can be adjusted to your preffered idling setting.
Hope that helps you out!
Thanks for using Fixya!
The specification calls for 900 rpms for the idle speed when warm for the 1987 Dodge Shadow.
One can adjust this with a screw on the carburetor, if it has one.
If it's fuel injected the idle speed is automatically controlled.
Fast Idle Speed HOLLEY 5220/6520
Fig. 5: Turn the adjusting screw with a screwdriver to raise or lower the fast idle speed — make sure that the adjusting screw is resting against the lowest speed step
NOTE: This procedure is performed while the carburetor is installed on the engine.
On 1981–82 cars, disengage the two-way electrical connector at the carburetor (red and tan wires).
On all years, disconnect the jumper wire at the radiator fan and install a jumper wire so that the fan runs continuously.
On 1983–86 models, pull the PCV valve out of the valve cover and allow it to draw underhood air.
Disengage the oxygen sensor system connector located on the left fender shield near the shock tower.
Ground the carburetor switch with a jumper wire.
Open the throttle slightly and place the adjustment screw on the slowest speed step of the fast idle cam.
With the choke fully open, adjust the fast idle speed to comply with the value indicated on the underhood sticker.
Return the vehicle to curb idle, then reposition the adjusting screw on the slowest speed step of the fast idle cam to verify fast idle speed. Re-adjust as necessary.
Turn the engine OFF, remove the jumper wire and reconnect the fan.
Reinstall the PCV valve and remove the tachometer. On 1983–86 models, reattach the oxygen sensor system connector, and remove the jumper wire from the carburetor.
Before adjustment, leave the carburetor alone for approximately one hour at 73°F (23°C).
Adjust the fast idle opening by turning the fast idle adjusting screw to the following specified values (drill diameter):
2.6L engines equipped with manual transaxles — 0.028 in.
2.6L engines equipped with automatic transaxles — 0.031 in.
Choke Valve Setting MIKUNI
Fig. 6: After tightening the choke cover lockscrews, cut the heads off of lockscrews A (total of 3 screws) and stake the heads of lockscrews B (total of 2 screws) with a blunt punch
NOTE: This procedure need only be performed if the carburetor is disassembled.
Fit the strangler spring to the choke lever.
Assemble the choke valve, aligning the inscribed line or black painted line on the tooth of the choke pinion with the inscribed line on the cam lever.
Temporarily tighten the new lockscrews.
Set the choke valve by moving the pinion arm up or down, align a punched mark on the float chamber cover at the center of the three inscribed lines, and secure the pinion arm with the lockscrews.
Install the choke cover and tighten the lockscrews.
Cut off the heads off of lockscrews A.
Stake the heads of lockscrews B using a blunt punch.
Vacuum Kick HOLLEY 5220/6520 NOTE: This procedure is performed while the carburetor is installed on the engine.
If the vacuum kick is adjusted to open the choke too far, the engine may stall or idle very roughly just after cold start. If it is adjusted so that the choke does not open enough, there may be black smoke in the exhaust.
NOTE: To perform this procedure, you will need a hand held vacuum pump capable of producing at least 15 in. Hg (50.6 kPa) of vacuum. The vacuum kick diaphragm may be damaged if you attempt to retract it manually. You will also need a drill or dowel which has a diameter equivalent to the specification for Vacuum Kick in the Carburetor Specifications Chart.
Remove the air cleaner. Open the throttle, close the choke and hold it in the closed position, and then release the throttle to trap the fast idle cam in the choke-closed position.
Disconnect the vacuum hose at the choke vacuum kick diaphragm. Connect a vacuum pump and apply 15 in. Hg (50.6 kPa) or more of vacuum.
Gently move the choke blade toward the closed position just until play is eliminated from the vacuum kick linkage (so that the vacuum kick is determining choke blade position).
Insert the drill or dowel into the gap between the upper edge of the choke blade and the air horn wall, toward the center of the gap. The dowel or drill should just fit into the gap. If necessary, rotate the Allen head screw in the center of the diaphragm housing to create the proper gap and then recheck with the measuring device.
Restore all vacuum connections and reinstall the air cleaner.
Remove the air cleaner
to access the carburetor.
Note the right side of
the carburetor where the accelerator cable is connected.
The cable is connected
to the accelerator cam which is stopped by the idle set screw.
The Idle adjustment
screw head is pushing down on a spring, which should help Identify the correct
adjustment screw.
Be careful not to adjust
the smaller mixture screws, unless you have a vacuum gage.
If your Idle is too high
you may get after run or knocking. I would set the timing then adjust the idle
afterwards. I hope this helps out since I do not know if the
carburetor is stock or not.
Most likely you have a Holley carb. You may have a 460 engine. If you have the carb with a big vacuum pot in front of the carb, then you have a RPM governor. The RPM governor will work against the 4 barrel.
The main mixture for the idle jets can be adjusted like any old style carb. You may have plastic caps over the idle screws but take them off. Then use a vacuum gauge on any intake fitting and proceed to read the vacuum level as you turn the mixture screws. You want the mixture to reach a maximum RPM, then evenly turn the screw in until the RPM drops slighty and then balance for smoothest idle.
After this step adjust curb idle and see if this helps when the 4 barrel kicks in. Holley has different springs for the vacuum actuated secondaries and they are color coded. If the carb is original it should be right, but if the carb is of unknown origin you can check the proper vacuum spring, main jet, power valve and so on in a good Holley book. The mechanical secondaries are also listed with clearances to hand adjust.
By adjusting the mixture screws you have set the engine to idle just below peak vacuum pressure. This means you should have more vacuum to work the secondaries.
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