bouncing idle

i have a '92 civic 1.5 and every now and then the idle bounces back and
forth between 1000 rpm to 1500 rpm, after i've driven it and put it in park.
i can put it back into a drive gear and the idle is steady again,
park-bouncing. but, while driving it runs smooth. everytime i start it it
revs to 2k rpm then slowly down to under 1k like normal, but it used to only
start at 1500. i recently had the motor out to replace the crankshaft, so
i'm leaning towards a sensor buggin out or not connected. any ideas where i
can start looking?
thanks, jeff

 

Start by doing an air purge and topping off of the cooling
system, per your owner's manual or the free online ones at
www.autozone.com . It will take 30 minutes or more for the
fan to come on twice, so be patient.

Certain engine control components are cooled by the cooling
system. Air in it will result in adequate cooling. In
particular, the EAC valve (or idle air control valve) on
your Civic is susceptible to this. Mine was; it had the same
symptoms as yours a year ago. Air purge fixed it right up.

Report back. Also, surf around the online manual at
www.autozone.com and you'll see it has a troubleshooting
chart for idle problems. E.g. you might need a new EACV.

 

I bottle of fuel injector cleaner in my 94 civic solved the idle issues for
me.
Rocky

 

i found it!! i checked out the eac because i recently replaced it after
breaking the plastic nipple off and the vacuum hose sucked up to my thumb!
hooked up the hose and the idle instantly smoothed out.. doh! i guess thats
what i get for slapping it together in a hurry!!!

Start by doing an air purge and topping off of the cooling
system, per your owner's manual or the free online ones at
www.autozone.com . It will take 30 minutes or more for the
fan to come on twice, so be patient.

Certain engine control components are cooled by the cooling
system. Air in it will result in adequate cooling. In
particular, the EAC valve (or idle air control valve) on
your Civic is susceptible to this. Mine was; it had the same
symptoms as yours a year ago. Air purge fixed it right up.

Report back. Also, surf around the online manual at
www.autozone.com and you'll see it has a troubleshooting
chart for idle problems. E.g. you might need a new EACV.

 

Your joy is contagious. Way to nail it!