not too long ago i swapped in an h22a. they missed some vaccum lines and i replaced them, but for some reason i think im still missing one...today i put the car in park (its an automatic) and the rpm's started fluctuating rapidly and the whole car started vibrating and the "check engine" light came on...as soon as i put it into drive it calmed down and i made it home...now when ever i start it, the rpms jump from 1200ish to 2200ish constantly...i have no idea where to start....any suggestions? Thanks

 

Sounds like a vaccum leak. Check the TB to make sure anything open is plugged. Check the IM for the same thing. The problem is on one of those 2.

 

is your CEL still on? you should get the code so then you will know what is going on. all you do is find the obd port and jump it with a paper clip. on a 5th gen prelude, the obd port is behind the passenger side kick plate, right under the cd player kind of. i'm not sure where it is on a 4th gen, but probably in the same place. after you use the paper clip, look at the check engine light as it should be flashing. long flashes are the 2nd digit and short flashes are the 1st digit (so 2 long flashes and 4 short flashes = code 21). you may have to jiggle the paper clip around to get a proper connection.