If you are inside the van, it is on the left side of the engine block, above the spark plugs, and is blue. The harness for this sensor goes over the engine, then back down to the back by the distributor, combining with several other harnesses. I have a photo o the sensor, but I'm not sure how to post it n this forum.

 

I don't know the year or the engine size of your van but, if it is like mine, a 1994 with a 4.3 V6 maybe I can help you. It could be one of 2 sensors. One is a coolant temperature sensor with 2 leads going to the connector or a knock sensor (rear) with a single wire to connector. I hope this helps.

 

Coolant temperature sensor. Single wire. Goes up and over the valve cover.

 

There's a map sensor just under the top hose on the bulkhead, a bit difficult to get to. other sensors on the air intake tube can be cleaned with an air flow sensor cleaner spray, available on Ebay or Amazon. videos on YouTube.

 

Located under top hose near bulkhead, bit difficult to get at, but whilst you're about it and have the hose off, I may suggest you clean the air sensor.