coughing/sputtering idle - 95 Civic EX 1.6 VTEC
 

95 Civic EX 1.6 VTEC
I replaced air filter, spark plugs, and PCV valve, and changed oil and used synthetic oil.
I have a small idle problem. It sputters between 500-900 rpm at idle. It is intermittent, but definitely a small problem.
What should I check next? Is this something I need to take in and have the professionals look at it.
Other than at idle, the car runs as it should.
Service engine light is NOT on.
Car does not stall.

Re: vacuum leak? 95 Civic EX 1.6 VTEC
 

the idle air control valve? you should diagnose the problem before spamming money at it.

Re: vacuum leak? 95 Civic EX 1.6 VTEC
 

+1 iacv. clean it + clean throttle body. before cleaning it, a quick test: warm up engine then disconnect the 2p connector on the iacv. rpm should drop to 450 and the CEL will come on since you disconnected it. if idle rpm doesnt change, you know its your iacv.

do an idle relearn after. your engine will still be warm and you need to clear the code you just caused. turn off car. disconnect battery for a couple minutes. reconnect. turn off all electricals (radio, heater, etc..) start car and let it run for 10 minutes. turn off car then go for a short drive.

fyi..suspect iacv only if it its surging after its warm. if i understand it right, iacv comes in to play after engine has warmed up. someone else correct me if i'm wrong.

If its not that, throttle air screw may need adjustment to help idle return to 750 rpm.

how has your mpg been? any other symptoms?

Re: vacuum leak? 95 Civic EX 1.6 VTEC
 

Ok, I cleaned my IACV, it wasn't real dirty, but the screen was a little clogged with dirt. I let it dry, then reinstalled.

Update:
Idle still coughing/sputtering at idle around 750 RPM.

Question:
Do I turn the idle screw clockwise or counterclockwise to increase idle speed?