I have 97 civic dx with a d16y7, I pulled the engine to replace the timing belt and clutch, now the engine is back in and its got this surging idle only when the engine is warm. The idle goes to normal when the map sensor is unpluged, so I was thinking map sensor is the problem, but then I was In the car while the idle was surging and I turned the blower motor on and the idle smoothed out to normal. Turned the blower motor off and the idle surges again, what do you guys think?

 

How does it drive other wise? Any check engine lights on?

 

Drives normal, no check engine lights, just surges when up to operateing temperature.

 

It is air in your coolant system. Happened to me before. Specifically, your Idle Air Control Valve (IACV). If you pulled your engine you drained your coolant. First, bleed the system of air. With the engine cold, take the cap off the radiator. Start the engine. Let it idle and keep filling the radiator when the level goes down. Keep doing this and you will see bubbles coming out. Do this until you don't see significant bubbles or until the engine is fully warmed up.

Next, take off your IACV on the back of the intake manifold. Clean the metal screen and make sure it is not plugged up. Reinstall and then fire up the car. Should fix your problem.

If that doesn't work and you suspect the MAP sensor, the factory service manual has tests for it. Search Google and download a copy of the factory service manual and search for the MAP sensor test to be sure if it is bad.

 

Thank you for the info I will bleed the coolant system and if that dosnt work try the other things you mentioned

 

I had the same problem and i solved it by bleeding the coolant and cleaning the screen however now i get a squeaking like noise after the car warms up on idle after i reinstalled my thermostat. If i take my thermostat out the squeaking noise disappears. Any thoughts on what that squeaking noise could be when i put the thermostat in? The cars not over heating or having any issues all hoses are hot and coolant seems to be flowing fine. So not sure why it makes that noise with the thermo in there. I bought two new thermos to be sure and both have the same results... could it be the water pump or something making the kinda like high pressure squeaking eee eee eee niose with the thermo in there causeing more pressure or something? any ideas or suggestions pleease