Can't get the idle adjusted properly, one minute it runs fine then the rpm's go up by themselves, I adjust the idle wait a few minutes and it does it all over again.

sounds like an air leak in the intake system somewhere. clean the carb, check for cracks.

Make sure your saw is about half full of fuel. It makes a difference on the adjustment. Start your saw and let it warm up to operating temperature. Then turn the saw off for a minute. So you can do the initial adjustments,

first using either a small screwdriver or hex screwdriver ...depends on what the 039 has.

Turn both the Low speed (L) and High speed (H) clockwise until they stop. The turn them both one full turn counterclockwise.

Then with the screwdriver turn the H screw slowly clockwise. You will notice it will start to run faster as you turn it. Adjust the screw until the saw is running smooth and fast until it starts to 'flutter" . Then turn it slightly back . This will get the proper RPM.
If it is running too fast,or too slow, turn the Idle Adjustment screw (IA)( it is an i not an L) counterclockwise to lower the idle or clockwise to higher the idle.

Put the brake on and let it idle. Then turn the saw different times to each side and up and down. If it turns off or sputters, turn the L screw slowly back a little to adjust it and that should give you the proper adjustment. Now , if there is nothing else wrong (like a vacum leak) your saw should run fine.
If you absolutely can't adjust it. Something else is wrong it is sucking air through somewhere. Take it to the shop. or if you can, DIY, then by all means do it.

you can not manualy set the rpm on your dodge caravan, it is set by your computer and your idle air control valve, if you are having problems with your idle being to high or low you may need to replace your idle air control valve, go to your local auto zone or auto parts store and get a new one, they are pretty easy to replace,just a couple of screws and a electric connection plug, the auto store should be able to give you the location of the part on your vehicle of where it is located.

i would try adjusting the throttle position sensor

Try adjusting your idle speed screw in neutral.

Check your throttle cable to make sure it's not being pulled while turning the forks.

Check your choke cable and make sure it's adjusted properly.

Is the idle speed set too low? If so, adjust it, using the idle speed adjusting screw, to the correct idle speed (900 RPM). If that's not the problem, then check for air leaks between the carburetors and the engine by spraying WD-40 around the intake manifolds with the engine running. If there is an intake leak, the engine RPM will change briefly when the WD-40 is sprayed near it.
Aside from that, there are two other things that can cause your engine to die when it should be idling: the idle speed mixture adjustment, or low cylinder compression. Of course, if it was idling fine before, and the idle mixture adjustment hasn't been changed, then do a compression check, first. To idle properly, each cylinder's compression needs to be at least 140 psi.

sounds like you have to adjust your idle, fuel injected or carburated?

You may have a bad control valve or regulator. Did you adjust the idle properly?

1. Disconnect the connector on top
2. Adjust idle to around 650-700k rpm
3. Reconnect the electrical connection

After reconnecting, the idle should jump up around 700-750k rpm.
The idle screw is fail safe setting in case the ecu cannot set the idle. The rpm's set by the idle screw are supposed to be below the ecu/stock idle.

If this doesn't work, you may have a dirty or bad Idle Air Adjuster and/or Air Regulator. For information on cleaning that, you can refer to this page http://s95014253.onlinehome.us/63104/157335.html

You can test the IAA by supplying power to the plug with the car off. Listen for any clicks or humming. That will signify that it still may be working but is possibly stuck. The Air Regulator is for high idle for warming up your car. It has a bi-metal spring inside that rotates a disc closing off an airway to bring idle to normal after a couple minutes. If it dies it will stay open and give you permanent high idle. If it gets clogged usually no high idle for warm up.
You can remove it and peer through the end. If you see a thin sliver of light, it's open. Connect 12 volts + & -, wait a few minutes and see if it's now closed. If not, it's likely dead. It can be opened and cleaned if that's the issue.

The H is for high rpm (Main mixture) and the L is for Low rpm (Idle Mixture). First turn in both screws all the way in and then turn them both out 1 and a half turns. Pump the primer bulb if the equipment has one. Start the engine, once it is idling, turn the L (Idle Mixture) screw out (counterclockwise) from the preliminary setting until the engine speed decreases (rich). Note the position of the needle. Now turn the adjusting needle in (clockwise). The engine speed may increase, then it will decrease as the needle is turned in (lean). Note the position of the needle. Set the adjusting needle midway between the rich and lean settings as in the picture below. Don't touch the throttle during this procedure. Once you have found the best idle speed for the engine then you need to adjust the high rpm. This process is the same as with the idle rpm process but you need the to hold the throttle wide open while you are adjusting the H (Main Mixture) needle on the carburetor.

adjust the RPM of the engine when the aircon is off that match the RPM of the engine when the aircon is on but not too much.