Idle revs up and down

[BravoTango]

Here's the situation: 1999 Honda Accord V6 engine idle surges after start up. Initially, idle climbs to 2000 rpm then drops down to surge between 1200-1700 rpms.

I've removed and cleaned IACV. The one chamber which contained coolant was clean and the other two chambers only had carbon deposits. Due to being secured by non-standard screws (5-points), I could not separate the electronics from the metal three-chambered piece.

I've also checked and refilled the coolant levels in the radiator and overflow tank. Unfortunately, after cleaning, the problem still persists.

Any suggestions are welcomed. Thank you in advance.

[jdm2010]

air idle seal . clean throttle really good reset idle memory when you turn car rev to 3k for 10 sec then let car warm on its own

[BravoTango]

Oops...I also should have asked this question.

How can I check if the IACV is faulty and is causing this surging idle?

[Targa250R]

Originally Posted by BravoTango

Oops...I also should have asked this question.

How can I check if the IACV is faulty and is causing this surging idle?

You'll often get a Check Engine light with DTC P0505.

If your radiator is topped off, the cooling system has been bled out properly, and the idle still surges, then chances are that the IAC valve is just bad. It's a pretty common problem with J-series V6es; I replace a lot of them for this problem.

[BravoTango]

Thanks Targa,

I disconnected the IACV and started the engine. It ran rough with rpms doing quick short up and down cycles around 1200.

I read other entries that the procedure to bleed the coolant is to run the motor with the radiator cap off for a few minutes. Is that correct? Any idea how long should this take?

If this proper bleeding does not remedy the surging, then I will get a new IACV. I just want to make sure since this part is quite expensive and I don't want to go about replacing too many electrical parts which can't be returned once installed.

Thanks for your professional contributions.

bkt

[BravoTango]

Thanks to all. Replacing the IACV corrected the surging idle...engine runs fine and idles at 1000 in neutral and drops to 800 when in drive.

But, now have CEL...don't know what it is for. I have tried several times to clear the CEL by holding RESET button and turning ignition switch to ON position.

I have read references in other threads saying I can obtain the exact code. I just need to (1) find the location of the plug and (2) what I need to do to get the code.

Thanks again.

[BravoTango]

Thanks to all. Replacing the IACV corrected the surging idle...engine runs fine and idles at 1000 in neutral and drops to 800 when in drive.

But, now have CEL...don't know what it is for. I have tried several times to clear the CEL by holding RESET button and turning ignition switch to ON position.

I have read references in other threads saying I can obtain the exact code. I just need to (1) find the location of the plug and (2) what I need to do to get the code.

Thanks again.

[Kevinpursuit]

Get the code and report back. The plug is under the drivers side dashboard, usually on the left side pointing down. If you have an Autozone close by they will read the code free of charge.

[Targa250R]

Originally Posted by BravoTango

But, now have CEL...don't know what it is for. I have tried several times to clear the CEL by holding RESET button and turning ignition switch to ON position.

That's the procedure to reset the Maintenance Required light. The Check Engine light cannot be checked and reset without an OBD-2 scanner tool, and in most cases it will not stay off unless the underlying problem is solved (usually related to emissions control systems).

You can temporarily clear the Check Engine light by disconnecting the battery or pulling the backup fuse, but then you won't know the error code(s) that caused it to come on. This will also clear all of the emissions system readiness monitors in the ECU, and erase your factory radio security code as well.

I have read references in other threads saying I can obtain the exact code. I just need to (1) find the location of the plug and (2) what I need to do to get the code.

The OBD-2 connector is located underneath the dashboard on the far left side, above the driver's kick panel. You will need an OBD-2 scanner to read the DTCs stored in the computer. As mentioned, most AutoZone stores will read them for you at no charge, but I don't believe they can reset the ECU. Also, don't let them try to sell you any parts based on their code diagnosis - I've seen a lot of people get suckered into buying parts that won't fix the problem and that cannot be returned.

[sharpshot189]

I have a 99 accord with a 2.3 and i have read posts with this issue.
Things I have done is
cleaned the throttle body 3 times
replaced IACV, TPS, MAP sensors, rotar, rotar cap, and spark plugs
replaced the hoses for the coolant on throttle body

There is a CEL and its for cylinder 1 misfire.
The sensors triggered the CEL too but they have been replaced.

The only way I have found to make the idle surge stop is to unplug the map then unplug the tps then once the idle calms to 1200 i plug the tps back in and leave the map un hooked this really jacks up fuel economy I would not recommend this at all. The tps clip is blue and the map is grey I say this because I read those harnesses could be backwards.

Final weird thing is the IACV is brand new however after the engine runs for 20-30 minutes the idle surge goes away but the car acts like the IACV is un hooked when its not unhooked.

[holmesnmanny]

You need to check for a vacuum leak. I'm not an expert on the V6's but if you're certain you don't have a vacuum leak then perhaps your base idle is set too high.

[Senile satsuma]

Fast idle valve is what a friend said he cleaned when his accord was having this exact problem. Idled at first until it warmed up then jumped back and forth between 1200 and 1900. After cleaning this the problem stopped

[holmesnmanny]

He doesn't have a fast idle.

[sharpshot189]

Still having the same problem anyone have a good vacuum routing diagram for the f23a 1999 accord engine?

[Senile satsuma]

I know he doesn't have a fast idle but that is what caused the 95 accord to keep reving up and down. It got cleaned and it stopped the problem

[sharpshot189]

Ok update-
I took off the top part of the intake manifold, the portion that has the IACV and throttle body connected to it, I cleaned it off and put it back on the engine and now my idle is holding however its holding at 2200