99EJ8

Hey guys, I have been having a stroke of bad luck with my 99 civic ex iacv. I know these tend to go bad after awhile. I tend to clean it once a month when i get a CEL code (P0505). My usual remedy is just to remove the ground from the battery and clean the valve with carb cleaner and reinstall. I know this is a band-aid and the CEL keeps coming back. The point of this thread is, my local junkyard just received a 97 ex with a d16y8 5 speed (same as my motor) however it is obd2a. I was wondering if i could interchange the obd2a iacv with my obd2b iacv, or are they different? Thanks for the help.


TL;DR - Can i use an obd2a iacv in place of an obd2b iacv?

Former User

For the D16Y8, you need to match the IACV with the transmission - auto and manual are different.

What is the specific idle problem that you have?

By the way, P0505 can be caused by not only a bad IACV but also a vacuum leak, misadjusted idle speed, bad ECT sensor/circuit, or bad TPS sensor/circuit. You should troubleshoot these other possibilities prior to swapping the IACV.

99EJ8

The car in the junkyard is a manual as is my vehicle. Most of the time the problem is a fluctuating idle. When i press the clutch in when coming to stop the rpm will drop to about 1500, hover, then finally come down to the idle speed which is set at 850-900 rpm. When the CEL comes on and i press the gas lightly it seems to sit at 1700 - 2000 rpm and the needle will bounce up and down. However, if i press the gas pedal down 50% or more, it'll accelerate as normal. If the car is in gear while normal driving and i let off the gas it seems as though the throttle plate shuts completely as it produces a more pronounced feeling than when you normally use the engine to slow down. Also when the car is in either first or second gear, and i don't press the gas enough while the CEL is on, the car jerks violently as it bounces as i described earlier.

turbociv910

It's fine. Some are 3 wire, make sure urs matches.

Former User

Check the input and output voltages from the TPS on the throttle body.

99EJ8

will do thanks.

amej8

I'm bumping this since it's a recent thread and I'm having a similar issue.

So Ron, if I adjusted my idle too high (around 1000), that could cause the P0505 CEL? If that's the case, I might just turn the idle screw back in (since that's how I originally adjusted my idle).

grumblemarc

iTrader: (4)

If you adjust your idle BACK to where it was supposed to be does the CEL go away? That would answer that question real quick and then you can go down the list and check each one off.

amej8

Ive been busy lately and completely forgot to do this. I'll have to see if turning it back in fixes the CEL. It used to idle around 4/500 and would almost stall every now and then which is why I turned it up.

Former User

Yes. Don't just turn the Idle adjust screw. Follow the procedure outlined in the service manual.

amej8

Well now, the problem is when I disconnect the IACV connector, the idle will hop up to 1500 and start bouncing back and forth (the problem that normally occurs with the IACV plugged in and when I'm not moving and at idle with the CEL on). Should I reset the ECU and then do it with the CEL off?

What's weird is even with the CEL off, the car still idles high and the rpm's still rev up and down anywhere between 1000 and 2000 (2000 if it's really cold). It drives completely fine, I just don't get the bogging problem I mentioned on ClubCivic.

Former User

John, your problem sounds like a leaking vacuum hose or leak from the throttle body or intake manifold gasket.

amej8

My friend and I looked at all my vacuum lines when we worked on my car 2 weekends ago and didn't see anything... A vacuum line was kinked and my friend straightened it out. I thought I was saved. Then the code came.

The only reason why I'm being skeptical about a leaky TB or IM gasket is that this started RIGHT after I cleaned my old IACV with brake cleaner (I waited for it to dry before installing it and running the car). So it's either just coincidence or my problems really do lie elsewhere... How would I inspect the TB? Something about taking the intake off and putting my finger over a hole on the butterfly? Also, I removed cruise control a few years ago and I put electrical tape over the nipple on the back of the IM. Is there something better I can use because the sticky residue is caked on the nipple now and the tape just slides back and forth (doesn't fall off). And no, there is no leak there, I've checked.

I realize even the smallest crack, kink, tear, whatever could cause a leak. Which makes it THAT much more frustrating to figure out. This is pissing me off lol.

Former User

John, I forgot that you have an automatic transmission. When you disconnect the IACV from an auto Civic, the idle speed should increase. That's normal. However, the fluctuation in the idle speed is not.

Again precisely describe your idle problem with the IACV connected. Am I remembering correctly that the idle speed with the engine warmed up is too low and also fluctuating when P0505 is thrown? Is the cold idle speed fine?

By the way, this is the proper procedure for adjusting the idle speed of your engine:

amej8

I don't have an automatic. I would never own an automatic lol. Although I'm starting to want one because I'm sick of driving... I just prefer to have a manual because I feel more in control of the car. Plus winter driving is easier with a manual.

And don't worry, I have a Haynes manual. I read it and I properly adjusted my idle. I think I fixed it FINALLYYYY. Usually when I turn on the car or blip the throttle, the rev's will bounce up and down a couple hundred before it settles at idling RPM. After I properly adjusted it, it only bounces once, then it falls to 600 (where I adjusted it too).

And usually the CEL comes on within a couple minutes of sitting at idle at operating temp. I let it idle for a couple minutes and it didn't come on. So hopefully P0505 is finally gone after only what...6 months?

dirtyharryhatch

Hate to bump an old thread but figured id just post here instead of creating a new one.
The car seems to ONLY surge when its at operating temperature.
Usually does it alot when im driving and does not stop. It usually starts when i get to a light or im braking to stop. As i was driving i received a CEL but never got to check what the CEL was.

Ive owned the car for 2 years without ANY issue at all as far as idle surge or a dirty IACV.

The car just started doing this 3 days ago after screwing with the idle (trying to raise it a bit since its been sat for 2 months straight sounded a bit low).

After it sat for 2 months and i got it running it didn't have that issue but for some reason (like a retard) The next day i tried raising the idle and this issue started.

The more i say this out loud the more it sounds like i need to adjust the idle screw.

Its a dx so there is no RPM gauge, should i just turn the idle screw till it stop's surging or something?

Livennine01

Had a 98 Accord that had the fluctuating idle. I was a little stumped at first but took off the IAC Valve. There were 2 - 5 Point Star nuts that I couldn't find a tool to fit. I drilled them out and then took the cover off and found the valve to be sticking. Sprayed some carb cleaner and used a rag to get the metal plunger thing moving. Then went down to the hardware store and replaced the bolts with hex head. Problem went away instantly! I think Autozone wanted $130 for the part.

ladude60

Just a warning to those contemplating buying one of those cheap chinese $40.00 IAC valves off Ebay---MINE DIDN'T FIX MY BOUNCING TACH NEEDLE!. After thinking maybe I had a vacuum leak (tested with fog machine, no leak found) and replacing the ECT sensor, still no luck. I managed to find an OEM denso part on Ebay for $140.00, installed it, PROBLEM SOLVED!!

NotARaCist

iTrader: (1)

While the input is appreciated, "Cheap parts are bad" is pretty common knowledge. Also, please don't bump a 2+ year old dead thread. Thanks.