Help me out here guys this is getting crazy. Everytime my car gets cold it has the up and down idle until it warms up a little bit. I have no cel codes, I cleaned the FITV and the IACV. No vacuum leaks.

The only way it starts going away is if I pump the upper radiator hose. For some reason I can't get all the air out of the cooling system I think, it doesn't leak anywhere though. Any suggestions? Its a d16z6.

 

If air keeps appearing in the cooling system, the head gasket may be bad. A small leak will do only this with no other symptoms such as white smoke or coolant in the oil. Or the radiator cap / recovery system is letting coolant go into the plastic tank but not return.

 

I was afraid of that. Will a compression test tell if its the head gasket?

 

Potentially, if the leak is bad enough, yes. I've also seen cars with a fully bad head gasket (i.e. burning coolant) return 'acceptable' compression numbers though. That said, I haven't had to do any comp tests on my civic yet, so someone else may have more insight into our cars specifically.

 

Had a slightly similar issue, no vacuum leaks, perfect compression/leak down, ect. I had a bad start and bad idles, I was worried about the head being bad but here is what I did to fix it. First I cleaned IACV, replaced all wiring for battery and made sure it was all snug and good and new fuel filter, this fixed my idle problem. I also had overheating and air in my system, for that issue I ended up replacing all the switches and sensors (incl thermostat) then still had the problem, so I had to replaced the radiator and heater core hoses (they do get old and can let air in but not leak any out at times) then parked on my driveway slope (mine is steep) and jacked the front of the car up (d16y7 no bleeder, so i need to be on a serious incline) then run engine with heater on full blast for a real 20-30 minutes so that the water cycles a few times, filling up the radiator when needed. Then after that I capped the radiator and have not had a problem since.

 

Well I definitely have something in my radiator fluid that doesn't look too tasty, so im assuming its oil, so I flushed a lot out and poured some bars stop leak stuff in it so maybe that will fix the little leak that I have. Im pretty sure thats the reason its doing it but if not ill be checking the fuel filter next. Well see how this goes!

 

Stop leak is unlikely to help, and likely to cause other problems. Get the radiator completely full, start the engine cold with the radiator cap off and rev it. If the head gasket leaks, steady bubbles will appear in the radiator (in a severe case, coolant will blow out, that is why you do this with the engine cold).

Head gasket denial runs deep. I've been there. Really not difficult or expensive to replace once you decide to do it.

 

Im not too worried about doing it I just dont have the biggest tool selection and I don't have a few days off consecutively so im trying to just avoid it until I have enough time to do it lol. Ill let you know how this goes.

 

Well I ran a full bottle of Bars leak stuff through the radiator and it didn't seem to help too much. Aside from it possibly being the HG, could it be from an intake manifold gasket aswell?