How to test Civic iacv

Tiny
HBSB2CARPROS
  • MEMBER
  • 2003 HONDA CIVIC
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 50 MILES
My car idles well, but acceleration bogs down (hesitates). Can the iacv cause this symptom? Iacv works like the old chokes in a carb engine.

Voltage test of ecm connector A(31p) pin 12 bl/red iacv valve, reads 9 volts w/igni switch on (ii), should be ~5volts, I took iacv off car attached 12v and it does close & opens after removing 12v. So I can assume iacv is ok? Or can it still cause hesitation upon acceleration? Also, any idea what the resistant values should be between the 3 pins?
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Sunday, January 30th, 2011 AT 9:43 PM

5 Replies

Tiny
KHLOW2008
  • EXPERT
Hesitation has nothing to do with the IAC.

Common fault for hesitation are low fuel pressure, bad spark plugs and related components.
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Monday, January 31st, 2011 AT 7:17 PM
Tiny
HBSB2CARPROS
  • MEMBER
I used fuel gauge to test fuel pressure; 42-44psi, I guess its ok?
Also removed ect sensor, checked resistance while applying heat, noticed the resistance reading dropped 300 ohms, so I guess the ect is ok? Next i'll check ignition timing w/ timing light, not sure what that will prove, if some sensor or sensors are bad and not sending correct infor to ecm to timing could be adversely impacted. I'm going through process of elimination trying to isolate. Compression test was good, fuel pressure good. I unplugged tp sensor, placed potentiometer across it to vary resistance and revved engine to see if engine would stop bogging down. I did this to try and determine if the tp sensor was bad. It didn't seem to improve anything. Idle is smooth, as I rev up the engine until it hits that boggy position at about mid throttle and engine starts to die. I've performed voltage drop tests on all grounds of ecm, found nothing. I've tried covering throttle valve opening while revving engine, engine would only die if I totally blocked throttle, naturally ( NO VACUUM LEAKS?). Because fuel pressure tested ok, can I assume its the engine is not starving for fuel? But, its the sensors that feed the ecm, and the ecm then tells what fuel mix to add to the air. Circular reasoning. Ecm is closed looped system how can one diag? What else should I be checking?
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Wednesday, February 2nd, 2011 AT 6:23 AM
Tiny
KHLOW2008
  • EXPERT
Is the CEL indicating?

Any trouble codes?

Have you checked the exhaust system for clogging?
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Wednesday, February 2nd, 2011 AT 4:45 PM
Tiny
HBSB2CARPROS
  • MEMBER
CEL is on, scanner can't read the ecm. I'm having to diagnose by trail and error testing (process of elimination) of everything connected to ecm. Don't have schematic wire diagrams which would be a big help. Haynes book doesn't have any wire diagrams except for simple things like lights, starting etc. Alldatadiy only has block type diagrams, no wiring diagrams.
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Wednesday, February 2nd, 2011 AT 5:57 PM
Tiny
KHLOW2008
  • EXPERT
Here are the schematics.
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Thursday, February 3rd, 2011 AT 3:50 AM

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