I have a 1994 Civic Si hatch, has the D16Z6, idle is really bad,starting up while cold, it will run like it should for 2 or 3 minutes and then the idle starts to surge from 1000 rpm down to 100-200 rpm or it dies out. I took off the IACV and cleaned it, did this twice, took of the FITV and screwed down the round plastic thing all the way down. I've read that if you unplug the IACV, you can tell if its bad or not, I unplugged it and my engine shut off instantly... is this normal, I thought it was just supposed to drop in idle speed.

The car has always had a weird idle since I got it, just not as bad as now, less then a month ago. I just finished doing a water pump and timing belt on it, would being off a tooth do this it? I'm 99% sure the timing is right but just thought I'd throw that out there too, I'd would think the engine wouldn't even run it was off a tooth....

yeah I read the big article about idle surge, just had more questions I guess, please help


Modified by racinmason85 at 2:53 AM 1/20/2008

 

that kind of surge is typical of a large vaccum leak at the manifold or TB. double check the bolts on the iacv to make sure they are tight. find the idle screw on the TB, and confirm it's not tighened all the way down.

the screws job is to set the baseline idle (aka, a controled vaccum leak between the tip of the screw and the passageway in which it fits.)

if you find that it's in all the way, loosen it about one full turn and try the iacv test. the engine should run with the iacv unplugged. keep loosening until it runs around 450rpm with the iacv unplugged.

otherwise, start looking for a leak. you can get some carb cleaner to help you here. let the engine warm up and idle. spray around the manifold and all of the vac lines, systematically, listening for any change in idle. (if i remember right, the carb cleaner should raise the rpm or steady the fluctuation when it gets sucked in through the leak)

 

I adjusted my idle so it holds a crappy idle at best, which is the best I could get it, when the iacv is unplugged. My problem seems like it only acts up now when its cold, goes from 1000 down to 100 rpm or almost dies. I don't know if I have a vacume leak somwhere or what, is it possible that I screwed down that round plastic ring too far inside the FITV, or maybe I just have an air bubble in the coolant.??