1988 Dodge Caravan engine idles up and down

Is the check engine light on? If yes, turn the key from off to on three times then leave it in on position on the fourth time, then count the flasshes.22 would flash as 2 blinks, then a short puase, then 2 more blinks. If several codes are stored, the pause is longer between codes, code 55 will be the last code. Do this and post all codes found. You may have a vacuum leak, get a can of spray gumout, spray the vac lines and maniflod area, when the idle changes, youve found the leak! You want the engine running and spray on the outside but do direct the stream onto the hoses, if it is a vacuum leak, the engine idle will change speed, then you have detected a leak, repair the vacuum leak and see how it runs! The other thing that it could be, and may not set a code, is the idle air control, it's bolted to the throttlebody.