Erractic Idle

Hi 1999 honda civic 1.4i just replaced throttle body with new
sensors,flushed rad topped up again,start motor in morning sits at 1500
rev,s comes down to 1100 then jumps up and down when fan kicks in goes
down to 800 stop at junction it goes up and down between 1100 and 1500
help required thanks.

 

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You've got AIR in the system, and it won't leave until you fill the
reservoir to MAX, and top it up two or three days in a row. The rad cap
allows the system to sip coolant from the reservoir as the engine cools.
If there's not enough coolant in the reservoir, it can't displace the
air it's trying to expel.

This was covered just a couple weeks ago. SEARCH is a handy tool, since
you dont' have to wait for an answer.


'Curly'

 

The cooling system should have a bleed screw which you can open when the
engine's cool in order to get the air out. Here's a description of the
bleeding procedure using the '95-'97 Civic as an example.

http://media.honda.co.uk/car/owner/media/manuals/CivicManual/pdf/10-4.pdf

Eric

 

Fast idle valve coolant passages are blocked. Or you've got an air leak
somewhere else.

 

I had surging idle....warm or cold.....turned out the intake gasket
had slipped out of place and allowed massive vacume leak.

 

Thanks everybody problem solved,new thermostat.

 

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Yeah, now that the coolant has been replaced, the idle will be stable
unless the reservoir gets too empty again. The manual says to put it at
MAX after any work has been done on the cooling system, since it may sip
a bit in the first few days.

'Curly'