88 preludse idle issue
 

Problem came on all of a sudden after bringing it out of storage last year. When the car sits it will idle normally and as it warms up it will drop like it should. However, if you move the vehicle at faster than say 5kph, the idle will jump to 2k and hold there until you once again come to a stop and stay stopped for about 2 seconds. So, if your doing 50, press the clutch in and the idle will be 2k and stay until however long it takes you to stop and sit. Any ideas?

Is an 88 Prelude 5sp with the b20A DOHC FI

Check you coolant lines for air. Check all hoses and stuff for leaks. They mess with your idle. Try checking and/or cleaning your IACVs

I have the same car, just fixed my idle after redoing the timing belt right before i read your post.

I left little information to see what people came up with but I have found and fixed the problem. I had check the fast idle valve, changed the iacv, and changed the tps 2 seperate times with the problem continuing. Finally put a meter to the TPS and found the signal was completely backwards. 4.5V at idle and .5V at WOT. Don't know how this happend, but since its just a simple potentiometer, I repinned the 5V input and the Gnd Ref wire and swapped them. Now voltage is the corect direction and all problems solved. Thanks all!