1992 Accord racing idle in park & neutral HELP Plz

1992 Honda accord EX 150K ..Idle jumps up & down ( 800-1900 rpm) in park & or neutral. Once tranny is engaged it stops racing up & down,
but is still too high (about 1200 rpm) Dealer can not diagnose..
After problem occurred I replaced the following. New plugs, wires,coil,cap, checked EGR and it seems to work fine,put in brand new $50.00 O2 sensor,just did the IAC= idle air control valve ( from junk yard since new one is 275.00). pulled fuel rail & cleaned the injectors , replaced the rubber gaskets that seat with the injectors. No visible or detectable vacuum leaks
Again when a load is on transmission it stops racing but still idles to fast. This is killing my MPG and sounds really bad LOL.
Any help is very appreciated...I am out of ideas
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JesseLittle wrote:

    Probably trapped air in the cooling system.     Take the radiator cap off, and open the bleeder valve at the thermostat housing. Start the car and close the bleeder when all the air stops coming out.     Might be the coolant sensor giving bad info to the computer, but I doubt it. bob
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N.E.Ohio Bob wrote:

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Bearing in mind the coolant reservoir has to be fairly full before and after you do this. If there's no 'reserve' in the reservoir, there's nothing to displace any air you want to get out.
'Curly'
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You have a bad coolant temperature sensor. That sensor sends info to the ecu to increase idle (cold start) and return to normal idle after the coolant temperature is at normal operating condition.When it goes bad, your idle will fluctuate up and down repeatedly. My Accord went through that, done that. Easy fix. Just don't confuse the coolant temperature sensor with the coolant sending unit if you fix the problem yourself. Have a good day. Jackson........ .....Semper Fi.
JesseLittle wrote:

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| >Any help is very appreciated My F20A too had this problem : cause was its throttle angle sensor. www.autozone.com/images/cds/gif/large/0900823d800cf4a6.gif www.d-a-p.com/askus.htm
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