I have a 93 civic si hatch. I bought it about a year ago, the guy i bought it from put a new d16z6 in it but didnt put the power steering and a/c back in it but it runs good. I went to get it smogged and the mechanic said it wasnt in testable condition because it surged at idle. he said that it may be because it is missing a power steering pressure switch due to the power steering being gone and that the computer is freaking out causing it to surge at idle. i went home and tried to pull codes but there weren't any so i wanna know if im gunna have to put the power steering system back in or if theres something else i can get away with to make the surge go away, if thats even the problem.

 

Does the idle rev up and down, or does it stay at a certain RPM which is too high? What speed RPM(s)?

 

it goes from about 500 to 1500 RPM. but sometimes it will idle perfectly at about 750, but its rare.

 

usually when it idles its surging thouggh

 

Possibly a vacuum leak (maybe a gasket or line), could be IACV or FIV... even the brake booster or cruise control could do that.

First, you could try turning the idle screw inward. Do 1/2 turn at a time and heat cycle the engine. It's a 93, so resetting the ECU may help recalibrate the new idle screw setting.

 

ive tried turning the idle screw out, it doesnt really do much. so im going to test to see if the FIV is the culprit, i havent looked into that yet. how do i know if the IACV is the problem? and so your saying that you think the PS not being installed isnt the problem?

 

I don't think PS is likely at this point in time.

Turning the screw out is going to raise the idle speed and introduce more air. Turn it back in and reduce the incoming air to lower idle. Just go turn it all the way in and see what happens.

I would turn the screw in first.

 

yeah ive messed with the idle screw alot. thats definitely not it

 

im gunna check the FIV tommorow

 

Make sure you have ether a P28 ECU or a Chipped ECU that can run vTEC. if not this could be the problem. i had a hatch with the same motor do this when running on a stock
P08 ECU

also a you can us carb cleaner to find vac leaks.

I have had a lot of Honda's with a messed up FITV and all of them had High idle's but never surged. If the FITV is just starting to go out of adjustment you will have a very high idle on cold morning start-up's but will idle normal when warmed up.

your best bet is a vac leak or dirty IAC.

Ok to set the idle on a D16Z6 Heat cycle the engine then shut off. Then unplug the IAC and start the car then turn the idle screw so the car idles at 420 +/- 50 RPM shut off and reconnect the IAC car should then idle at 670 RPM Manual or 700 Auto

 

alright ill look into all of that. thanks man