Probably.

 

Replaced the MAP Sensor.
No change. 🙃

 

Compression Test.

 

150psi cylinders 1, 3, 5, 6
120psi cylinders 2, 4

 

2 and 4 are low... but still theoretically "acceptable".... Do you have specific misfire codes? The fact that they are next to each other, and the 'odd men out', is mighty suspicious though.

 

I get misfire codes for cylinder 3 or cylinder 4. It will throw codes for one for a couple weeks and switch to the other for awhile. If I'm at idle and pulling wires off plugs, the engine doesn't drop when I pull 3 or 4. Drops on all the others.
Van behaves normally on the highway.

 

Try running some seafoam thru it. See if that makes any difference.

 

Yup. I do seafoam in the fuel semi-regularly and I did a seafoam upper engine treatment earlier on.
It's been a puzzler!

 

Since 2 and 4 are next to each other and both have the lower compression reading, there is a strong possibility of a leak in the portion of the head gasket between them.

 

That's what I was thinkin' too.....