My 1998 dodge ram van check engine light was just on for three days and it just went out today its it ready for emissions test

You must perform an OBD2 drive cycle to make ready for testing.
Toyota Drive Cycle for Setting Smog Check Readiness Monitors

• Fuel tank at 1/2.
• Engine cold start idle for 10 minutes.
• Drive at highway speed 55-60 mph with steady throttle for 16 minutes.
• Return to idle for three minutes with engine running in park.
• Drive again at medium speed 40 mph for eight minutes.
• Return to idle for three minutes.
• Repeat next day.

probably when there are no fault codes recorded.

Take it to autozone or another place like it and have them read the codes and tell us what they are.

You have not run a OBD2 electronic engione control fault code test, get a code reader and do that first and don't replace anymore parts until that is done and you have the fault codes and have done the proper diagnostics for each code.

may have cracked vacuum lines.

Check the spark plug wire and spark plug on #8!

I had a similar problem with my Dodge truck.I replaced the cap, rotor, plugs and wires and the check engine light went out. Within 4 days the light came back on with codes for multiple misfires..To make a long story short, I put electrical tape on the wires to adjacent cylinders and the problem was solved. Answer; The pluig wires they are making for Dodge are really cheap!

the idle air control is on the back of the throttle body. it has a plug going to it and is held to the throttle body with 2 screws

Two things you want to know about the check engine light on any vehicle. One is it's an emission warning. The most common cause is a loose gas cap, make sure it clicks when you gas up. Second, is that being an emissions light, is that it'll require some test equipment to find the problem if you checked the gas cap and it's tight. You will want to do that at your friendly Dodge dealer. Why? They'll not only know what it is, it might be fixed free in the emissions warranty which has some parts that are covered longer than the vehicle's regular warranty. The shop on the corner doesn't do warranty work and they're not going to tell you if it might be covered.

Bring it to a parts store, most will scan for engine trouble codes for free. They will plug a hand held scan tool into the vans diagnostic port (under the dash) and 'read' codes stored in the van's computer. They can tell you what the codes mean, and suggest how to fix it. If you have any further questions at that time, post them here with the code #'s. Good luck. Curt