Accord Idle Surge
 

2000 Accord V6

I'll be as brief as possible, but I want to provide as much info as possible, so please bear with me.

Alternator number 3 went out, and the car has 95,000 miles on it, so I thought I'd change the timing belt and water pump when I replaced the alternator.

When I got it back together, it started right up, idled at 1500 RPM for a few seconds, then started surging very rhythmically between 1100 and 1800 RPM.

After reading a lot of stuff here and elsewhere on the Net, I became convinced that there was air in the cooling system. There are no provisions to bleed the system, so I raised the front of the car, removed the cap, etc. and went through the motions. At first I saw air bubbles, then they gradually stopped appearing. The idle problem continued.

Once, after idling like that for a while, it started fluctuating very rapidly between 1800 and 1850 RPM and flashed a code. Unfortunately, I have cleared it, and it won't come back.

At this point, the car will start at 1100 RPM when cold, then start the surge after 5 minutes or so.

This isn't my first rodeo, and I doubt that I got the timing a tooth off. Also, there is no apparent loss of power, which would indicate that the timing was off.

I have a hard time believing that there is a problem with the IAC circuit since the car was running fine before, and it's not stumbling like cars I've seen before with bad IAC valves.

I can find no disconnected plugs or open vacuum lines.

If any of you have any suggestions, please enlighten me. Thanks in advance.

Re: Accord Idle Surge
 

Inspect the egr valve it might be clogged.

Re: Accord Idle Surge
 

I had the exact same idle surge problem on my 2000 Accord V6.....and I had not even changed the timing belt. In fact, I did nothing except park the car in the garage for 2 weeks while we were on vacation. Car was running fine before we left, get home....car starts right up but then surges from 1100 to about 1900rpm. For me, the issue was the IAC valve. I had some troubles with it in the past with the idle stumble/low idle as you had mentioned. I took it off, cleaned the IACV and throttle body, reassembled and I was good for a few months until the surging issue occurred. I was told the surging occurs when the IACV sticks wide open (makes sense...too much air feeding the engine) making the engine race....however when the engine speed reaches a certain point with 0% throttle position, the enging controller cuts the fuel, bringing the engine speed back down....at which time the open IACV takes over again......and the idle surge "dance" continues. I was tired of nursing my old IACV, so I just replaced it and my problem is gone. You may try just removing yours and giving it a good cleaning with some throttle body cleaner. Most of the time a good cleaning seems to solve the problem.

Re: Accord Idle Surge
 

Provided that you got all of the air out of the cooling system, the problem is pretty characteristic of the rotary air control valve underneath the throttle body; it's a known problem with the J-series engines. They will typically stick after sitting unused for a long time. I don't know of any fix other than replacing the valve. Unfortunately, a new one is $164.

Re: Accord Idle Surge
 

Thanks for the input. I'll be trying these things out this weekend, and will let you know how it goes.

As far as the rotary air control valve... Is there a way to test it? Or is it's operation/functionality obvious when you get it off the car?

Re: Accord Idle Surge
 

Thanks again for the replies. I don't get much time to work on this car, so it's taken me a while to respond.

Removal of the IAC requires removal of the throttle body; there are phillips head screws on the IAC that you can't get to with the throttle body on the car. My useless Chilton's says there are 12mm bolts.

When I removed the throttle body, I noticed the intake manifold had oil puddled up in it, which prompted me to check the PCV valve. It was bad, and I replaced it.

I removed the IAC valve, and cleaned it up the best I could with carburetor cleaner and a soft brush. Still have the same problem. I've learned a little since I started this project (I work on old muscle cars, not modern economy cars... Usually), and I can see how this thing is supposed to work. If I unplug it, the idle stops fluctating as much, and goes to the fast fluctuation at around 1800 RPM. There is a lot of air being pulled into both orifices in the throttle body, and if I partially block the rectangular one, the idle will slow down and smooth out. There is no effect if I block the round one as suggested by the Chilton's manual.

Oh, I pulled a code on it even though the check engine light wasn't on - yes, I know that it will throw a code for unpluging the IAC - this was before I unplugged it. It was 505 Generic Idle Control System Malfunction.

I'll get a chance to work on it again next weekend, and I'm planning to buy a new IAC valve. I just wanted to post here first, before blowing $150, to get feedback from the experts if there is a better way to test it, or if there's a more likely culprit.

Re: Accord Idle Surge
 

P0505 will almost always show up with a bad rotary air control valve on a J-series.

No idea how to test or repair it. Our shop just replaces them with new. Works every time.

Re: Accord Idle Surge
 

That was it. It's amazing that the thing decided to stick at the same time that I changed the timing belt.

Thanks a bunch for the input.

I hope I can get a couple thousand more miles before the next problem manifests itself. I expect the transmission to go next :crook:

Re: Accord Idle Surge
 

Just to clear up a detail within this important thread...
'Targa250R', and 'TxSuperDuty' seem to describe two different parts: 'Targa250R' mentions the "IAC valve"; 'TxSuperDuty' mentions the "rotary air control valve". They refer to the same part: the "IAC Valve" (or just "IACV"), Honda p/n: 16022-P8A-A03. (Interestingly, the Honda Service Manual refers to the thing as the "IAC Valve" (or just "IACV"), while the Honda Parts Catalog refers to it as "Rotary Air Control Valve".)

It is not uncommon to experience engine surging (a.k.a., "idle hunting","throttle pulsing", the phenomenon goes by many names...) upon engine start up just after completing a timing belt replacement job, particularly where the idle was perfectly normal before doing that job. The connection is, believe it or not... coolant! Coolant drains from the engine with the removal of the water pump. The IAC valve, which lives at the topmost part of the coolant circuit (under the throttle body on '00 3.0L VTEC V6 engine) uses coolant temperature to actuate. If an air pocket forms within the IAC valve body, it'll malfunction, which manifests as engine surging with no corresponding P-code. The simple fix? Perform a thorough and proper air purge of the coolant system BEFORE you suspect a bad IACV!

Btw... there is a short list of components that should not be replaced with an aftermarket part. The IAC valve is one of these parts. If you are determined to replace the IACV, only use genuine Honda p/n: 16022-P8A-A03.

Re: Accord Idle Surge
 

What happens if u use after market iacv? Im having issues with my car i have codes 0505 pending and 0420 i changed the egr and iac valve already but used aftermarket iacv from autozone could that be my issue. Im 2500 into this car and its only wortg 1500 and i just bought it 2 weeks ago i feel like i got ripped off i just wanr it to pass inspection but i cant gwt those 2 codes to clear. The 0420 just came up after i changed thw iac valve and egr valve. I put some fuel treatment in there and that was all. Now sometimes when i start it it bogs out like its misfiring or not getting fuel and thwn works fine after a few min and it only does it after i drive my car for a 10 min or so. The only codes i have thrown are 0505 pending and 0420 even when there cleared thwy come back please please help

Re: Accord Idle Surge
 

You don't mention in your post if you performed a proper engine coolant air purge procedure after you installed your aftermarket IACV. Coolant flows thru a chamber in the IACV. The IACV just happens to reside at the highest point in the coolant system. An air bubble trapped in the coolant chamber within the IACV can cause wonky behavior that possibly manifests as idle surge and/or a P0505. Watch the following video carefully--pay particular attention to the introduction monologue:

Hopefully, your engine runs without issue. Plenty of folks claim to use aftermarket IACV in their car with no problems--maybe there's a list of reliable aftermarket IACV brands on the web. But if you're getting P0505, the ECU doesn't like your aftermarket IACV. T'shoot the connector and the harness continuity first. Otherwise, replace the part.

That's a problem unrelated to the IACV, and only tangentially connected to the EGR (if even that). Hunting down the source of an emissions system DTC is a pain in the butt because they tend to be gremlins. Fortunately lots of info is available within this forum and elsewhere that will guide you--and your digital multi-meter--through the process of chasing down the source of the odious "P0420". And should you determine that the one or the other O2 sensors (both expensive parts) are bad, resist the impulse to purchase aftermarket and purchase either genuine Honda or Denso.

Re: Accord Idle Surge
 

I have a 1999 Accord V6 and is experiencing absolutely same problem (I left my car in the garage too for 2 weeks). Let me see if cleaning or replacing the IACV will solve my problem. I will update. Thanks