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hello, a couple months ago i bought a used 2000 honda civic ex.
would like to keep it running well for my son,

it developed a surging idle problem. i have taken it to 2 mechanics around here and hey have not been able to solve the issue.
I looked on line for solutions and of course the most talked about thing is IACv...........replaced valve and nothing. still idle surging and code P0505.
after changing my intake, checking TPS, ECT sensor, Map sensor and everything else i could think off I finally noticed what I now know is the Air Assist valve was not closing when up to temp.
I was so happy when i found information on it and of course my luck would be it is only on 99-00 cars and most people don't know about it,
ordered it, replaced it and crank that baby one more time ..........IDLE SURGE. WTF?????
did an idle relearn multiple times and about 20 different ways........... same crap.
what gets me is its almost instant. as soon as i turn the car on it goes into an iddle loop.........IAC opens surges up untill like 2k rpm then closes goes down to 1.5k rpm and wash rinse repeat...........it drives me crazy now.

if i unplug the iacv it purs like a kitten but as soon as i plug it in it goes buzurk.

does anybody have any suggestions? I'm out of ideas and can't find anything else to try.
Thanks so much in advance for your help.

 
Rep Power: 211

Did you purchase a genuine (OE/OEM) honda IACV or an aftermarket?
Smoke test for vacuum leaks?
Follow vacuum line from cruise control to intake..sometimes the intake side falls off and can create a surge.

This may help if you haven't already read it: https://honda-tech.com/forums/honda-...-here-2127246/

 
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hello,
I purchased an IACV from my local Orileys, but was thinking of trying another one, or somehow try a known good working one. on my to-do list
I did the throttle body spray test for vacuum leaks did not successfully find anything, checked all lines and nothing.

I also was planning on checking for leaks by blocking throttle body with something like a book. if it keeps running it means it is getting air from somewhere else, and if it dies means no leaks right?
just trying to think outside the box, this issue has me irritated to say the least.

Thanks for your help. I"ll report back after i look for leaks again and if i can try another IACV.

 
Rep Power: 211

Not saying that aftermarket won't work, but OEM is a better choice

Hard to get to the underside of intake gasket with spray..unless you had it on a lift or crawled under with engine running? Smoke test us less risk and IMO better results

Not necessarily..I doubt a small vacuum leak would keep it running.

 
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thank you,
i'll look for a video on how to do a smoke test.......

Look up Scotty Kilmer's smoke test on youtube. He uses a cigar and works well enough on these small engines.

 
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I had a friend of mine look for vacuum leaks with his smoke machine and he said there are no leaks.
he also suggested i get a Honda IACV said that could be the issue.

I got a Honda IACV and the surge went away after doing an Idle relearn then came back.

I am out of ideas.
would the oxygen sensors have something to do with the idle?
could bad or weird oxygen signals confuse the ECU?

 
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Performed most of what was mentioned. #3 coil pack bad.. Eng. light off. IAC clean. TBody clean. Only problem now dips to about 400 rpm (auto. Trans.) at idle with a/c ON.?? Base idle with a/c OFF is perfect (950-1000) after valve adjustment. Then again it's upstate N.Y. we only get to use a/c about 3 week a year.( heater doesn't affect idle) Thanks .!

 
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<br />there is a type of ammeter in my 01. May be in all of this generation in the fuse box under hood. (It looks like a relay with a flat bar going thru it.) Apparently it measures current drawing off electrical load +sends to ecu + tells alternator to switch to high or low output (higher at idle since low rpm). Normally this will turn CEL on. I found the previous owner had pulled harness off, but oddly no CEL was displayed. Hooked back up CEL on and code for that part.I would look into that. I forget what its called but it was $50. Ammeter regulator or somesomething. Its the ELD (electrical load detector) just a thought .

 
Rep Power: 211

Have you checked mechanical timing?..the timing belt may have skipped a tooth. Also, check ignition timing (distributor) with a timing light + jumper the service connector. Another item to check is valve's adjustment.

Other than that you'll need an OBD2 live data scanner for o2 voltages and long + short term fuel trims. It could be related to the ECU but you'll want to rule out other possibilities first

 
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almost sounds like the EGR valve is stuck open a little bit

 
Rep Power: 223

no egr on those cars

 
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oh ok than