I have had a rough idle since I finished my hf vx swap. I have replaced all ignition components and meticulously checked for vacuum leaks. When I pump the brakes the idle jumps from 700 to about 1500. Is that normal or could this be the leak I've been looking for. Can somebody that has experience with this help me fix this idle problem. When I shift into neutral while coasting the revs hang at about 1000rpm and then drops down and runs rough.

 

Can somebody pump his or her's brakes while the car is idling and tell me how much the idle surges. Thanks in advance.

 

pumping the brakes and the raised rpm is normal it means your brake booster is normal but it should raise slowly not fast. It sounds like you need to adjust your idle a little higher. By your dashpot there is a little allen screw with a nut on it nut = 8mm and screw 2.5mm allen. Let your car warm up disconnect your iacv on the back of your intake manifold and adjust it 900 rpm or wherever you like it.

 

maybe try using a brake vacuum valve from a vx?

 

I have already set the idle speed. It's at 750. Stock is 600 +-50. Do you know how when a vacuum leak is bad the idle surges up and down. That's what it does when I pump the brakes. I checked the timing and with it fixed using the SCS every few go rounds it will be way off. All the ignition components are new. Except the dizzy. I took the guts out of a 98 dx and put them inside of the housing from the vx.

 

have you cleaned out your IACV(idle air control valve)Also I found my idle was a lot smoother after i had cleaned off all the ground wires in the engine bay,just my 2 cents best of luck.

 

I cleaned the IACV and the grounds when I first started having this problem.