Rough idle

**Alfrance05** · August 3rd, 2015 11:32 PM

Honda civic ESI

Roughly idles when the ac is off (600-700) but when the ac is on it idles at 500 rpm and the ac clutch is constantly turn on and off.

Things done:
1. Compressor was checked: no problem
2. Throttle body was cleaned
3. IACV was cleaned
4. TPS and MAP sensor was check and was functioning well

Engine coolant temperature sensor went caput so i just shorted the socket for the meantime just to turn on the rad fans.

Does the rough idle resulted from the shorted ECT socket?

**Heisenberg** · August 3rd, 2015 11:48 PM

ECT switch has no connection to rough idle. Try to do the ECM reset procedure to relearn the idle. Make sure you follow it vigorously. The ECU checks all the load and adjusts the idle based from it. I do it everytime I have my A/C system recharged or if there are additional electrical loads.

**Alfrance05** · August 4th, 2015 12:38 AM

Ok try ko bukas. Thanks!
Pero sir, diba the ECT will provide the information to the ECU for it to learn the temp of the engine and trigger the radiator fan and the sensors on the throttle body?

**pdspd** · August 4th, 2015 10:16 AM

Sir,ang ECT sensor ang nagbibigay ng signal sa ecu kung malamig ba or nasa normal operating temp na ba ung makina.Bka Radiator cooling fan switch sir ung cnasabi mo na ginawan mo ng DIY para umandar fan.
Magkaiba sir ung switch chka ung sensor.Check mo ulit,bka magawa mo.Goodluck...

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Sir,ang ECT sensor ang nagbibigay ng signal sa ecu kung malamig ba or nasa normal operating temp na ba ung makina.Bka Radiator cooling fan switch sir ung cnasabi mo na ginawan mo ng DIY para umandar fan.
Magkaiba sir ung switch chka ung sensor.Check mo ulit,bka magawa mo.Goodluck...

**Stigg ma** · August 4th, 2015 10:36 AM

grabe ang dami sensor... hindi pa yata na imbento yan mga yan nung panahon ng civic ESI...

ano ba makina mo? EFI na ba yan?

**jaypee10** · August 4th, 2015 03:10 PM

pa silip mo sa timing light baka hindi naka tapat,,
nagpalit kanaba ng air filter spark plugs,

baka puro umido nadin ung distributor cap mo.

yan kasi ginagawa ko sa 95 esi ko dati.tapos may adjustment ng hangin dyan sa may pinaka throttle niya pwede mo isara bababa ang menor pag binuksan lalakas.

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pa silip mo sa timing light baka hindi naka tapat,,
nagpalit kanaba ng air filter spark plugs,

baka puro umido nadin ung distributor cap mo.

yan kasi ginagawa ko sa 95 esi ko dati.tapos may adjustment ng hangin dyan sa may pinaka throttle niya pwede mo isara bababa ang menor pag binuksan lalakas.

**Heisenberg** · August 4th, 2015 04:53 PM

Originally Posted by pdspd

Sir,ang ECT sensor ang nagbibigay ng signal sa ecu kung malamig ba or nasa normal operating temp na ba ung makina.Bka Radiator cooling fan switch sir ung cnasabi mo na ginawan mo ng DIY para umandar fan.
Magkaiba sir ung switch chka ung sensor.Check mo ulit,bka magawa mo.Goodluck...

Magkaiba po ang ECT Switch and Sensor. Actually 3 po yan. Yung isa "ECT Sending unit".

ECT switch - shorts to ground and activates the fan at a certain temperature
ECT sensor - sends signal to the ECU when operating temperature is reached
ECT sending unit - sends an analog signal to the temperature gauge on our dashboard

Halos magkakatabi lang yan. Pero yung ECT switch nasa thermostat housing.

**Alfrance05** · August 4th, 2015 09:22 PM

After posting my query, i changed my spark plugs, distributor cap, and air filter but was not able to cure the problem. Baka engine timing yun problem, pa check ko muna sa mekaniko ko.

And yes, EFI na yun civic ESI.

**Alfrance05** · August 4th, 2015 09:44 PM

How do you know if the IAC is bad? After it was cleaned, i removed the socket and the engine died so it means that the IAC is good right?

**Heisenberg** · August 7th, 2015 03:58 PM

Originally Posted by Alfrance05

How do you know if the IAC is bad? After it was cleaned, i removed the socket and the engine died so it means that the IAC is good right?

The IACV adjusts the air intake when additional loads specifically the A/C is turned on. Sobrang bigat ng compressor so the ECU raises the RPM on the background. This is done through the IACV, more air passes by. That's why it's called Idle Air Control Valve. In reality mga 1500 RPM ang nadagdag na speed pero makikita mo sa tachometer mga 250RPM lang. That means mga 1250RPM ang kinailangan ng aircon mo.

All of these speed are calculated and learned by the ECU. So again, it's necessary you perform the Idle Reset Procedure from the manual. Andun yung mga correct RPM etc with and without load.. pag mali na yung sayo, most likely kelangan mo palitan IACV mo.

May note din dun kung ano gagawin pag namatay ang engine pagkadisconnect ng IACV connector. Supposedly hindi mamatay. Pwede mo adjust yung idle through the screw.