Idle revs up and down
 

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.

Re: Idle revs up and down
 

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

Re: Idle revs up and down
 

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

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

Re: Idle revs up and down
 

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.

Re: Idle revs up and down
 

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

Re: Idle revs up and down
 

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.

Re: Idle revs up and down
 

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.

Re: Idle revs up and down
 

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.

Re: Idle revs up and down
 

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.

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.

Re: Idle revs up and down
 

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.

Re: Idle revs up and down
 

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.

Re: Idle revs up and down
 

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

Re: Idle revs up and down
 

He doesn't have a fast idle.

Re: Idle revs up and down
 

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

Re: Idle revs up and down
 

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

Re: Idle revs up and down
 

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

Re: Idle revs up and down
 

i have a 95 honda accord, 4 days ago it got real cold out, and i forgot to put antifreeze in my water, i went out next morning to start car it seemed like it didnt wanna turn over then i heard it turn sound like water pump broke ice then i remebered i forgot o add antifreez, i cut car off, checked radiator everything was froze. i iwent back to start it and let it run to maybe help defthaw it. my car started idleling up and down, i let car sit for and hour or 2 to dethaw. all line were dethawed i drove to store tp get antifreez then was on my way to school and car started over heating so i pulled over added antifreez cuz my radiator apperently water is running out somewhere. filled it up with antifreez then drove a mile or 2 again and started to over heat. when i mean over heat the car didnt run hot it just went alil past half so i pulled over new something was wrong antifreez steam was coming through my car under dash. the steam was being pushed out of my coolant storage. after that i checked my lines again and noticed that my bottom hose to the radiator was still soild ice. idk if i broke blades on water pumper when i first started it. or there is just a slit leak somewhere from where the ice has cracked something. i have 2 problems. the idle reving up and down, and now a lose of water. i have checked the oil no water in it. im a pretty good motor person but not sure what is going on. please give me all options here this vehicle is my only transportaion to school and work. need to get it fixed this weekend before school. please and thank you

Re: Idle revs up and down
 

Well when water freezes it expands. When water in a sealed system has no were to go it will expand the container that it is in. therefore you could have multiple cracks/leaks in various places. if the block was frozen solid then I would say you probably did something to the water pump as well as possible damage to the block itself.

You will need to let the entire system thaw in a warm garage and then do a pressure test on the system. This will show you were the cracks/leaks are. A low coolant level can cause a surging idle.... you will need to fix the cooling system before you trouble shoot the idle.

Re: Idle revs up and down
 

Re: Idle revs up and down
 

Hi all my auto 1993 Honda Accord had leaking water constantly but fixed it yesterday with K-Seal 236ml so that problem finally fixed.. But now the rpm is jumping up and down while car on but in P and very loud while sounding as if engine (not sure if its actual engine but sounds like it) also going up and down as if revving high then low,high,low etc While rpm showing matching it? All oils have been checked and fine, though maybe once it heats up to correct temp, sound will settle but didn't make a difference?? Plz help as I can't work out why and how to fix? Other than that car has no other issues..tia

Re: Idle revs up and down
 

Did you check and clean your FITV?

Re: Idle revs up and down
 

im having the same issue but i have replaced the map sensor, idle air control valve, cleaned the throttle body, replaced throttle body gasket and purged air from the coolant system and nothing is helping still surging once it warms up after 10 sec. its a 2001 honda accord lx 4cl

Re: Idle revs up and down
 

Do you have a CEL?

The most likely issue is a vacuum leak, use carb cleaner, spray around the manifold to engine gasket, injectors, plenum gasket, throttle body gasket, MAP and IACV gasket (don't spray the TPS). Check that all the vacuum lines are plugged in properly. If all that checks out do the following:

Remove the intake duct between the air filter and throttle body. Start the engine in this configuration. Find the IACV air hole in the inlet area of the throttle body, with your finger partially cover the hole with the throttle closed. Was the surging idle reduced? If so the IACV is probably stuck open or the IACV motor is not working properly or the connector has issues. Try striking the valve body with a screw driver handle (not the motor).

Re: Idle revs up and down
 

I just had this prob on my 92 accord. If your car has a secondary system like mine it needs to be replaced. The part I had to replace is called Air Boost Valve. It made my car surge like crazy rpms up and down driving or not. Look at the diagram to see if u have it. If so start the car and when it starts to surge up n down tap on it with the butt of a screwdriver. It will stop instantly if this is your prob.

Re: Idle revs up and down
 

Vacuum leak for sure. Check all gasket surfaces for leaks, as mentioned above, Throttle body, injector O-rings, intake manifold and check all vacuum hoses hooked to the intake manifold/throttle body for cracks.

The F23 Accord does not have an air boost valve, idle air control valve or fast idle thermal valve. It uses an all in one valve called a rotary air control valve. It is located in the same location as the previous generations IAC valve, on the backside of the throttle body/intake manifold. This valve could be the cause of an erratic idle issue if it is not completely closing when the engine is warm. Always a good start removing it and checking the O-ring gaskets and cleaning any carbon deposits from the RAC valve as well as the ports from the throttle body and intake manifold.