97 Transport starts then won't start

My van had been sitting for about three months without being started. I got done what was needed this last weekend and started driving it. Had no problems and then on Sunday I went to start it and it would crank but wouldn't turnover. All the lights and dings are working. On Monday i went to start it and it started right up. The idle was hesitant and would race at times. It stopped doing that and was fine for a couple of days and as of this morning it wouldn't turn over again. I should probably also mention that I can't remember the last time it had a tune up. Van has 133,000 miles. Any advice would be greatly appreciated.

Also if anyone can tell me why my windshield wipers are staying in the up position it would also be greatly appreciated.

I do not have the specifics on the 3.4 but this make me think of:
- EGR valve: specially if it sat there for several months, it might stick opened at times...
- faulty idle throttle valve is often related to wavering idle speed

Reading stored codes would be a good start: this one needs the scan tool for a reading.

I took it in yesterday and the mechanic coded it but it passed. I put some fuel system and injection cleaner in yesterday and I am getting a tune up on it this morning. I'm not very knowledgeable but I was thinking it was the EGR valve also. I had one go on another vehicle. I hope it's not that, kind of expensive. Thanks for the info. Any more would be greatly appreciated.