Mechanics

HIGH IDLE AND SURGING

1998 Honda Accord • 6 cylinder 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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Paul767
December 15, 2010.



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)

Mhpautos
Dec 15, 2010.
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?

Tiny
Paul767
Dec 15, 2010.
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)

Mhpautos
Dec 15, 2010.
Will try first thing in the morning. Let you know what happens. Thanks so far for the fast reply!

Tiny
Paul767
Dec 15, 2010.
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)

Mhpautos
Dec 15, 2010.
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?

Tiny
Paul767
Dec 15, 2010.
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)

Mhpautos
Dec 15, 2010.
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.

KHLow2008
Dec 15, 2010.
The iac I replaced was brand new.

Tiny
Paul767
Dec 15, 2010.
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.

KHLow2008
Dec 15, 2010.
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