vg_Ace

I know I know another jumpy idle thread but this one I just can't figure out even with the search function.

Here is what happens while driving: after the car warms up on cold days the idle will never stick. It will jump from 1000 RPM to 1500 RPM whenever I pop it into neutral. Almost everything on the engine is new or rebuilt. No matter what the idle will just keep jumping until it finally calms down then it will catch and stop jumping.

The only mods I have are a CAI and a header and exhaust. But i don't see how this could affect the IACV from not sticking.

Also and I don't know if this is connected to my first problem but sometimes when the car is warmed up and I am just sitting at a light my RPMs will just slowly drop and drop and drop until the engine goes down to like 200 rpms then finally the idle will jump back up to 1500 then it slowly goes back to normal. What is causing this?

New IACV (less than 1000 miles on brand new unit)
New radiator with no radiator leaks whatsoever

The engine is the stock D15B6

Projekt_Ef9

It sounds similar to the problem i am gaving with my D15B. I have narrowed my down to a vacumn leak on the intake manifold. Im not sure if it is one of the tubes or that little plunger thing on the side of the mani. i would bet u have a vacumn leak though. Spray the vacumn lines with starter fluid and see if the idle rises when u do so. If it does there is a crack on the line you sprayed when it jumped.

vg_Ace

i was thinking that too and I have tested some of the lines but not all of them. By the time I can stop my car and pop my hood the idle evens out and stops.

I am going to try and do extensive testing this weekend to try and track down something, but if it was a vacuum leak why does it only really jump in colder weather?