High idle and surging

Tiny
PAUL767
  • 1998 HONDA ACCORD
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 179,000 MILES

My first time so bare with me!
Working on a 98 accord v6. Car sat for a year due to a no start problem. Thats what I was told. Towed home spent ten min charging batt and checking fuel and spark. Everything check out so used a little starting fuild and car started up sounded surprisingly good other then a instant idle surge from about 1200 to 1800. No check engine lights! Read a few forums and the iacv seemed to be the best place to start. So replaced it and cleaned throttle body and replaced gaskets. Put all back together and at first start up seem to run fine with a little higher idle then normal but after a min it began to surge again. The surging last about a min and ran at high idle unless I give it gas then it surges for about a min again. I ended unplugging the map to see what would happen and the idle dropped and seem to run smooth with no surge. So I figure I would put a new map sensor in. After I did had same issue! Started up fine with about a 1200 idle once it warmed up it surge for about a min then stop at a high idle. I unplug the new map sensor and the idle dropped and smoothed out but of course the engine light comes on. I check for vac leaks, cleaned egr ports, did a tune up but still have the idle surge a nd high idle. Read a few threads that honda's need to relearn the idle and some have idle adjustments but not sure is this year does thatand not sure it will take care of the surging! Any help would be great!

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Wednesday, December 15th, 2010 AT 7:15 AM

16 Replies

Tiny
MHPAUTOS
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Lots of info that's a good start, now have you done a scan? Not all faults will set a MIL, so do the scan and eliminate the possibility of any unresolved fault code to start with, re post with your findings so that we can move on if there still is an issue to locate.

Mark (mhpautos)

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Wednesday, December 15th, 2010 AT 7:26 AM
Tiny
PAUL767
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Scanned with no fault codes! The only codes there where ones I put there by unplugging the map and iacv. Another? When I unplug the iacv when engine is running it start to surge all the time not sure if new part is faulty are not?

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Wednesday, December 15th, 2010 AT 7:37 AM
Tiny
MHPAUTOS
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I had a talk to a Honda tech mate, he suggested to reset the ECU (pull the 7.5 Radio/Backup fuse in engine bay fuse box for a minute).

Air contacting the engine coolant sensor will also cause the ECU the mis adjust the idle, a re set may stabilize this.

Worth a try,

mark (mhpautos)

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Wednesday, December 15th, 2010 AT 8:56 AM
Tiny
PAUL767
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Will try first thing in the morning. Let you know what happens. Thanks so far for the fast reply!

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Wednesday, December 15th, 2010 AT 9:26 AM
Tiny
MHPAUTOS
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As I am in Australia, the time difference will act against us a little so if you don't hear from me, I will be back on most evenings my time, now its 8-45PM here so thats a bit of a guide for you.

Mark (mhpautos)

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Wednesday, December 15th, 2010 AT 9:43 AM
Tiny
PAUL767
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Okay! Do I need to let the car relearn the idle or is that something earlier years had to do? Also when un plugging the iac when running and it starts to surge is that what it's supposed to do or is there a problem?

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Wednesday, December 15th, 2010 AT 9:47 AM
Tiny
MHPAUTOS
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I will have to check up on any specific re learn, but I feel that for yours there will be none, IAC reaction van be a bit erratic when un plugged as the ecu is trying to compensate for loss of input signal.

Mark (mhpautos)

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Wednesday, December 15th, 2010 AT 9:51 AM
Tiny
KHLOW2008
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If the IAC replaced is a used unit, that coudl be the cause of the problem. IAC would often seized when left unsed. As mhpautos said, low coolant level can cause surging, ensure the coolant hoses to the IAC are notclogged.

Check for vacuum leakages. Any vacuum leakage would increase the idling speed resulting in the surging.

If you look at your old IAC, there is a spindle inside that can open or close. If you gently push at it, it should move without any resistance. Use carb cleaner to clean out the dirt and retest if it moves and returns to position smooothly. If yes, renstall this IAC and retest.

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Wednesday, December 15th, 2010 AT 1:42 PM
Tiny
PAUL767
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The iac I replaced was brand new.

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Wednesday, December 15th, 2010 AT 7:39 PM
Tiny
KHLOW2008
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Surging is caused by higher than expected idling speed and any vacuum leakages can cause that.

Have you tried to adjust the idling speed? After cleaning the throttle body, air passages have increased air flow and the idle adjust screw could be allowing excessive air into the manifolds to increase the idling speed.

Check the PCV.

Disconnect the air intake hose.
Start engine and when the surging occurs, use your finger to close the lower port inside the throttle body. If idling speed remains high, it is not the fault of the IAC.

If closing the upper port reduces the idling speed, the idle adjust screw is out of specs.

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Wednesday, December 15th, 2010 AT 11:43 PM
Tiny
PAUL767
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Pcv is new, just replaced! Just pulled fuse to see if that helps.

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Wednesday, December 15th, 2010 AT 11:54 PM
Tiny
KHLOW2008
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If it is the fault of the IAC or its controlling circuit, the PCM is the likely cause.

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Thursday, December 16th, 2010 AT 12:01 AM
Tiny
RED-LEG
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This is interesting. My wife's 2000 Accord V6 with 156,000 miles just began exhibiting this EXACT same behavior today. Those 156K miles have been absolutely trouble free. The only things remotely out of the ordinary lately is that it has been very cold here the past week and the car has sat for the past two days. I'm taking it to the dealer in the morning for a service and will report back with their findings.

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Thursday, December 16th, 2010 AT 4:08 AM
Tiny
KHLOW2008
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Exact trouble does not mean same problem. It cold be anything foem low coolant level to a faulty PCM.

If the Check Engine Lamp is indicating, you need to retrieve the trouble code to understand what had gone wrong.

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Thursday, December 16th, 2010 AT 1:25 PM
Tiny
RED-LEG
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In my case, the IAC valve needed to be cleaned.

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Friday, December 17th, 2010 AT 2:02 AM
Tiny
KHLOW2008
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Thank you for the input.

Quite often cleaning the IAC would resolve idling problems if no trouble codes are present.

Glad to know you have your problem fixed.

Have a nice day.

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Friday, December 17th, 2010 AT 1:10 PM

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