Hi guys,

I've searched a lot on the forums but something strange happens in my Civic.

I tried to clean the IACV and the car runs ok when is warmed up, but in cold starts and sometimes in warm starts the idle surges between 1500-2500 rpm. There is no vac leak.

If i unplug the IACV the car runs flawlessly and idles at 750rpm. The problem is i have the idle screw all the way clockwise closed. Sould the idle be 750 with the screw like this?

Thanks in advance.

 

Clean the FITV, search the forum for FITV, Fast Idle Thermo Valve.
side note, stock hondas are finicky with adjusting things. When there is a problem dont automatically start twisting adjustments, you will just make things worse. Once the original problem is fixed, then feel free to experiment with adjustments

 

Thank for the answer, but my engine doesn't have a FITV. I don't know if this engine make it to the US as it's a D15Z8 from a Civic MB3 fastback, the one that shares chassis with Rover.

 

When the IACV is unplugged, you should adjust the idle screw so that the idle speed is 450 RPM. If you close the idle screw all the way and you still have a higher idle speed than this, you have another issue. Vacuum leak... wrong PCV valve... gasket or vacuum hose leak... fuel injector seal leak... something.

 

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ThankS.

Will check today. I suspect it can be the PCV. As for leaks I tried to spray carb cleaner in every possible hose or seal but no change in RPM.

Will update with more info.
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Good news, I unplugged the PCV hose and let it suck air which seems to have unstuck it.

Did idle relearn and got 500 rpm with idle screw fully closed.

After that I let the car get cold enough to try a cold start and didn't want to ignite after a few tries I adjusted the screw to the left a bit and it seems to work.

Will do some more cold starts to see if this happens again.

Thanks a lot for the help.

 

Well, still surge at cold start, as soon as it warms a bit the surge stops and idling starts to go down till service temp.

 

Do you have a genuine Honda PCV valve or one from an auto parts store ? If you have the latter... go and buy one from the former.

 

I have the original. I will go buy a genuine one but lemme ask if it's a good idea to spray some carb cleaner at the hose from the PCV so It can suck it

 

At last i found the problem (Or what it seems to be, let's see how long it works). I unplugged the IACV again and cleaned it effortlestly with carb cleaner, although it didn't show any more signs of dirt, this seems to have unclog something as the car runs as brand new.

I will now start to restore the bodywork. Can someone answer me if the difference between MB3 and MB6 bumpers are the lips?