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Vehicle:
2000 Honda Civic (not sure trim level)
I believe the engine layout was D16Y8, based on reading the '96-'00 Service Manual
However, the engine must've been swapped at some point because the block is clearly stamped D16Y7.
Manual Trans, 5 spd
175,500 miles

Here are some past pictures from my other thread, FYI:
http://imgur.com/2z157vV
http://imgur.com/IpdzI2e
http://imgur.com/JVHbIsF
http://imgur.com/mZfwFlb
http://imgur.com/15R1W08

Additional weirdness: besides the motor swap, at some point I believe an A/T version of the throttle body + IACV was swapped in place. I recently replaced the IACV trying to eliminate P1509 code. I put the A/T version back on it because that's what it's had all this time before.

I just got my car back from my mechanic, who: replaced the exhaust valves, reworked the head, replaced cam seals, replaced timing belt, replaced water pump, and replaced broken motor mount. That work was a long time coming, the result of low compression in cylinders 1 and 2.

Unfortunately, my guess at the compression problem (which I thought was a simpler idle problem) lead me here:
https://www.civicforums.com/forums/3...e-posting.html
https://www.civicforums.com/forums/1...e-up-mods.html

as well as other similar postings discussing how to clean the IACV/TB, etc. That's what started this problem. I cleaned the IACV + TB, put it all back together w/ a new TB gasket, and got a new code: P1509. Disassembled and reassembled several times and ended up getting pissed off and just replaced the IACV. P1509 went away and I carried on dealing w/ the low compression problem. You can read all the details of these shenanigans here: https://www.civicforums.com/forums/2...e-routing.html

I decided this was worth making a new thread, because the topic is fundamentally different from the compression problem I was trying to deal with in my old thread.

-----------------------------------------------

Well, I got my car back about 2 weeks ago and two days after it threw code P0505: Idle Control System malfunction (see: pg. 11-192 of service manual). Situation very similar to this guy: https://www.civicforums.com/forums/1...-tps-help.html

Here's what happens: I get in the car, initially tach reads ~ 1500, and it'll either: flutter ~ 1300 to 1800 back and forth OR it'll come down to ~ 1000 rpm after 10-15 seconds (more normal idle). The problem seems intermittent. It really doesn't become a noticeable problem until the engine warms up. I drive along fine, but once the motor gets hot, when I take my foot off the accelerator the idle doesn't want to come down much, so that when I press the accelerator again, it jerks forward violently. When I take my foot off again, it'll jerk again. It's like it's become MUCH more sensitive to pressure on the accelerator, but I guess this is just due to the idle not coming down like it should.

Lately, I've been reading LOTS of threads about vacuum leaks, especially the dreaded "unhooked cruise control hose" problem:
http://www.clubcivic.com/board/showthread.php?t=182186
http://honda-tech.com/showthread.php?t=2543952
https://www.civicforums.com/forums/1...know-what.html
(this is not a complete list of what I've read)

So, I've been checking vacuum leaks around the intake. I took the hoses off one by one, the engine would surge, then I'd plug them back on and the engine would slow back down. I tightened up the hose clamps for these things too. So far, nothing is standing out as the problem.

Also, I took the air cleaner tube off, started the car, and plugged the upper port (pg. 11-193). This is where things get weird: first time I did this, the idling seemed fine (~900-1000 rpm), and I'm thinking to myself "oh great, now that I want to troubleshoot it's not going to misbehave!", so I plug the upper port and it wants to stall out. So, I get in and push the accelerator a few times, because this can make it flutter 1300-1800 or so back and forth. I get it to flutter, plug the upper port, and idle doesn't change at all. This is why I say it's an intermittent problem...

According to the service manual, pg. 11-192, the problems could be:
1) IACV malfunction
2) TB clogged / improper adjustment
3) Intake gasket manifold leakage
4) Intake air hose loose leakage
5) Vacuum leak
6) ECT sensor incorrect input
7) TPS incorrect input ('96 models only)

Here's my train of thought:
I doubt it's (1) as it's only about a month old (new, replaced). Doubt it's (2) because I cleaned the old one and left all the adjustments the same when I put it back in place. I don't believe it's (4): the hose clamps are all tight and the filter is in place. I don't have a '96 model, so I don't think it's (7). That leaves: (3), (5), and (6).

I'm hoping to save (3) for last, as that's the most work to replace It could still be (5): I have not looked from under the engine - maybe there's some other hoses under the intake that I can't see. Also, I have not followed the hoses further than the ports on the intake itself: I haven't gone over to the EVAP canister. Maybe I should? I'm not very confident the problem is (6) because I'm not seeing other codes related to the ECT sensor, but I suppose it is still possible. I suppose there could be an 8th cause: hacked wiring from 2-wire M/T IACV to 3-wire A/T IACV could have come apart or something. I'll lump (8) in with (3): a bigger deal to replace, as I'll have to take the intake off.

Other oddities: since many of the other threads show people overlooking other symptoms, I also noticed: when I got the car back from the mechanic, the Air Conditioner seems to lose it's "cool" when I come to a prolonged stop at a traffic light or something. When I get back to moving, it cools down quickly. I recharged the system only 2 yrs ago or so and it's normally ice cold no matter if I'm moving or not. So, that's different. Not sure it's relevant though.

Sorry for the wall of text. Hopefully it'll resonate with some people.

What should I TRY next?
I'm hoping there's something incredibly obvious that I'm missing...

 
Rep Power: 518

Return to the mechanic, he JUST had all this apart. Maybe he didn't get something perfect.

I KNOW if this happened after I did a big job like that at work, I would be married to it until the problem is corrected.

Make certain the cable from the gas pedal has plenty of slack so the throttle can return to fully closed position.



The RPM isn't surging from 2000-1200 repeatedly?


Rather than follow them all around the car, simply use pliers to squeeze the rubber vacuum hose(s) shut. If the RPM stays the same then it was not a leak.


Could be low charge, could be an inoperative fan, could be normal due to compressor efficiency drops at idle RPM.
You know the idle speed and IAC airflow changes as the engine temperature warms up, right?


Does the throttle body have one upper port or two? If that original IAC valve on the back of the manifold were sticking open, is there a passage in the throttle body that can feed it? I see the hole in the manifold, but what about the TB?

Oh crap that's a big pic.


----


I don't remember if I mentioned this one on your other thread..... Crank this screw in a turn or two and see what happens? (Make sure to note the original position so you can put it back if you have to.)

 
Rep Power: 0

Well, I was able to get my hands on a OBD scanner. Here are the results monitoring the car while sitting in my driveway idling after a drive home on the interstate (car was warmed up completely):

ABSLT TPS % 9.0
Engine Speed 1450 - 1550 rpm
Load ~25%
MAP kPa 25 (40 when I pressed lightly on the accelerator)
Coolant degF 190-200
IAT degF 116 (down arrow? not sure what that means)
IGN Advance (deg) 23.0
ST FTRM1% -1 to -8 (jumping around)
LT FTRM1% -4.6 stable
O2S11 V 0.135 to 0.740 (oscillating)
ST FTRM11% -2.2 to -7.5 (oscillating)
O2S12 V 0.095 to 0.115
ST FTRM12% 0.8 to -6.3 (oscillating)
OBD2 STAT CA

I've never used a scanner before, so I'm working on figuring out what these things mean. Feel free to comment on these readings if you know what they're telling me

 
Rep Power: 518

I don't see much there, just higher than normal idle RPM.
Temps look normal, fuel trims aren't out of line.

Is the RPM steady in that area? Not surging repeatedly?
Did you try cranking that screw in?

 
Rep Power: 204

Several trims of the 2000 Civic were offered with the D16y7....I doubt it was swapped.


D16Y7

Found in:
1996–2000 Honda Civic DX/VP/LX/CX
1998–2000 Honda Civic Special Edition – SE/EX (Canada)
1996–1997 Honda Del Sol S
1996–1997 Honda Civic Coupé LSI
Bore and Stroke: see D16 Series Engines
Displacement: see D16 Series Engines
Compression: 9.4:1
Power: 106 hp (79.0 kW, 107 ps) at 6,200 rpm
Torque: 103 lb·ft (140 N.m) at 4,600 rpm
Redline: 6,800 rpm
Rev-limiter: 7,200 rpm
Valvetrain: SOHC (4 valves per cylinder)
Fuel Control: OBD2-a MPFI
Head Code: P2A-2
Piston Code: P2E
ECU Code: P2E

 
Rep Power: 0

Ok, it's been a while since I've looked at this problem. I finally have a little time to troubleshoot this issue. Let me try to describe the issue a little better:

I start the engine. Idle is high, though that may be understandable since it's cold in the mornings. The idle surges slowly: 2 - 3 seconds to rise from ~1600 to 2200 rpm, oscillating back and forth.

After driving for a few mins (presumably as it reaches operating temperature), it goes into a "fast surge"? I'm not sure what to call it. At idle, the engine jumps between, say 1750 and 1800 rpm and stays really tight on that number. It pulses between the two bounds at ~ 2 to 3 cycles / second, much faster than before. Therefore, any time I hit the accelerator or let off the accelerator, the car will "jerk".

After starting the engine cool, I tried squeezing the vacuum lines as you suggested in the highlighted areas:
https://i.imgur.com/EyxiKNu.jpg
https://i.imgur.com/CNOjnbJ.jpg
No change in surge

My Google-ing has revealed that air in the coolant can cause this problem. What is the procedure for purging the air? I could just leave the cap off the radiator until the temperature gets to nominal, or should I just drain the radiator and refill it?

I fear the splices by the previous owner adapting the IACV from the manual to the auto version could have come loose or something, but of course they spliced them way down below the intake. I don't think I can reach them without removing the intake and I'd like to save that option for last. On the other hand, this problem is really predictable - same thing happens every day. I would think a wire being grounded randomly would not be so predictable. I don't want to go this route until I've exhausted everything else.

What should be my order of attack for this thing?

I forgot to note: the code is P0505, idle control system malfunction. The IACV was just replaced a few months ago.

 
Rep Power: 518

Did the other thread cover any of this already?


Pull the intake snorkel off the throttle body and cover the open ports in the throttle body with your fingers. Which ones can you cork to make the idle speed drop to normal RPM?


That IAC valve on the bottom of the throttle body, make sure that sucker gets screaming hot with antifreeze when the engine warms up. If it isn't hot then there's a flow problem or a bubble problem?

That fat hose (red arrow, pic below) that runs between the injector area and the intake snorkel, pinch that one off and see if idle drops.

 
Rep Power: 0

I don't think the other thread covered this. I have done the TB hole-closing tests before, but I can't remember the results, so I'll have to redo it tomorrow.

Tonight, I took the radiator cap off and started the car. Let it run for several minutes until it got to temperature. I saw very little air bubbles throughout the process. When I started the car, it immediately jumped to 2200 RPM or so, then gradually came down to 800 RPM or so. Soon, it got to idling nice and smooth at ~ 600 RPM. I waited a few minutes and lightly tapped my foot on the accelerator. The tach then jumped up and started surging. It kept doing so the whole time.

Is that hose you pointed to the PCV valve hose? I'll pinch it tomorrow and see what happens.

The most recent work I had done to this car was back in August: I had a local mechanic do a valve job on it, replace several valves and adjust the head, replace water pump and timing belt. I don't know if any of that is relevant, but that's the latest changes.

 
Rep Power: 0

ezone, I decided I would go outside and try these tests. First, the pinch hose test. I'm assuming that's the hose to the PCV valve. I squeezed it w/ needle-nosed pliers for a few seconds at a time while it was surging after the engine warmed up. No change in surging. I'm going back out to do the TB suction tests now.

Edit: TB port test results:

Here's what I did:
1) Start car, let idle, had to tap the accelerator a couple times to get it to start slow surging
2) Plugged lower hole during slow surge, result: idle returned to normal and stopped surging
3) Plugged upper hole during slow surge, result: idle returned to normal and stopped surging
4) Repeated a few more times with same result. After a few more minutes, it started fast surging
5) Plugged lower hole during fast surge, result: idle returned to normal and stopped surging
6) Plugged upper hole during fast surge, result: idle returned to normal and stopped surging

Edit: went back out and tried test again:
1) Restarted car, had to tap the accelerator a couple times to get it to start surging
2) Plugged lower hole during slow surge, result: idle returned to normal
3) Plugged upper hole during slow surge, result: no change, still surging

While I was inside typing this, I heard it start fast surging, so I went back out to test that again. Before I could get to it, it stopped bouncing, but was acting like it normally does in fast surge: it tries to stick HARD at 1800 rpm. If I give it a hard tap on the accelerator, it'll shoot up over 1800 rpm, but fall immediately to 1800. It won't drop below, and bounce around 'til it hits 1800 again. It'll fall directly to 1800 and stay there constant, never below. I don't know if this is important, but if I very lightly hold the accelerator while it's doing this, it'll fast surge between 1800 and say 1850, and won't go above at all. This is what makes it "jerk" me around when I'm driving. I have to give the accelerator a good mash to be able to drive at all.

4) Plugged lower hole during this condition, result: idle droped to normal
5) Plugged upper hole during this condition, result: idle reduced somewhat, but still high


So, uh, what does all that crap mean?

 
Rep Power: 518

Now THIS sounds perfect!

WTF? Why'd you have to go and do that for?

Bigger question becomes: What changed?

IDK, what's it go to? Where's your PCV valve?

You know, all those non-factory hoses with oversized hose clamps just scream vacuum leaks to me.

Um...It's broke, it's freekin broke.


Basically all of that kinda indicates the issue is mostly in the dual IACs and throttle body.

3 ideas.

One, plug up the passages for the unused IAC valve on the back of the intake to just eliminate it as a possible cause of problems. I'd unbolt the IAC (2 12mm bolts), take a shirtbox or cereal box and cut a chunk out to completely cover the machined area where that valve bolts on, then bolt the valve back on and squish the cardboard in there like a gasket.
(Back in the olden days, we used to actually "peen out" our own gaskets using cardboard.)


Two, Since you tap the gas pedal to get it to start surging, makes me wonder if the throttle body has worn out shaft bushings allowing the blade to **** slightly crooked when there's vacuum in the manifold. Wouldn't be the first one I've seen like that.
Does the gas pedal ever stick closed and you have to POP it to get it to work?

Three, the IAC under the throttle body would be all that's left after that? Didn't you say it was already a new one?

 
Rep Power: 0

I'm reading through the manual now to try and figure it out. I don't think it is, because it connects to the breather, before the TB. But, I only see 1 "breather tube" in the manual, and from my pictures, it looks like there's two. This is the one you pointed for me to pinch:
https://i.imgur.com/Z3YkuWA.jpg

Some other pictures. Don't know if they're helpful:
https://i.imgur.com/bqsO58L.jpg
https://i.imgur.com/W6BZIaB.jpg
https://i.imgur.com/totvsyy.jpg
https://i.imgur.com/qhdljmF.jpg
https://i.imgur.com/tZtB2oc.jpg

Maybe I should just bite the bullet and break everything down to the intake manifold gasket. And replace the splice joint while I'm at it.

I can certainly close up the old IACV, though it's been the way it is for > 6 yrs, so I have a hard time believing it would suddenly become an issue. Not saying you're not correct, just thinking of likelihoods.

What do you mean stick closed? Like idles high? And I have to give the gas pedal a quick pump to get it to idle down lower? Maybe. I haven't really been paying attention to this. Maybe I should start doing so.

Yes, it's brand new. Bought it in August. I still have the old one.

 
Rep Power: 518

You must be using a camera like mine, set at freekin huge resolution.


I wouldn't unless it's a vacuum leak or something. Just seems like work.

What splice joint?

I'd actually be trying to use the correct IAC (the one on the back of the manifold if you have manual trans???).... Even if it means juggling wires at the computer and hacking in a different connector to do it.

IDK, the engine is only supposed to have ONE IAC valve operating, and your extra one apparently has become a vacuum leak at times.


No, not like having anything to do with engine speed. I mean physically pushing the gas pedal down, just the initial movement.....Does it stick when you first try to move it gently? Gotta push hard or pop it to make it move?

 
Rep Power: 0

It's my cell phone camera.

I mean the joint where the previous owners hacked in the 3-wire IACV plug where the original 2-wire IACV plug was. Best I can tell: the car has a M/T and the 2-wire IACV is the unused one; they replaced the TB w/ the A/T version which has the 3-wire A/T version IACV, so they had to splice in the 3-wire A/T IACV where the 2-wire M/T IACV was. No idea why they didn't just fix the original hardware. I'll guess they did it because they probably had the A/T version lying around and didn't want to buy a new M/T IACV.

I'm not opposed to that, but I'd have to replace the TB w/ the M/T version and buy a new M/T IACV and tear down to the intake manifold gasket, because the ECU wire bundle is under there and that's where they made the splice. I can't get to it w/ my hands otherwise.

Oh. No, it doesn't seem to do that.

Edit: I just thought of something. All this trouble started when I replaced the IACV. I was careful at the auto store to buy the A/T version of the IACV even though the car is a manual. I also replaced the TB gasket just because. I wonder if I grabbed the wrong version of the gasket by accident. If that's the problem, does that mean I need to use the A/T version to match the A/T TB I'm using or do I need the M/T version to match the M/T intake? Is the intake different between the versions? Eh, maybe it's not a problem. I think I just laid the old one over the new one in the store to see if they match. I've got some pictures of it somewhere:
https://i.imgur.com/mZfwFlb.jpg
https://i.imgur.com/JVHbIsF.jpg
https://i.imgur.com/IpdzI2e.jpg

Ok, I definitely used the A/T version. Here's the comparison between the two:
https://i.imgur.com/NHgv2k1.png

So, scratch that idea. Man, thought I was onto something!

 
Rep Power: 518

If you buy an IAC for a manual trans, you should get the one on the back of the manifold.
Not sure how important the differences in the TB gasket are, as long as the correct passages aren't blocked off and no vac leaks.

MAYBE the MT TB gasket would block off the AT IAC ports?


IDK why some people go to such great lengths to complicate simple ****.

Block off the IAC under the throttle body, wire up the original (use jumper wires to test it with) just to see if it will work?


Any idea if the IAC wiring at the PCM was moved around for the AT IAC? The MT 2-wire version uses a different set of ECM terminals.

 
Rep Power: 0

Alright, I've got some time to look at this again. I decided I would look at the wiring to the IACV. There is so little slack on my connector, I had to take the intake off to get to it. I plan to look for breaks/cracks/etc. in the connector wiring and splice in some extra wire so I don't have to do this again. I can also look for a manifold gasket leak, though I think it's unlikely. Then, I'll work my way back up to the IACV and vacuum hoses again.

I took the intake off today. I don't see any manifold gasket cracks. The gasket seemed to be in good shape:
https://i.imgur.com/lpGLdX5.jpg
https://i.imgur.com/FEr6zHY.jpg
https://i.imgur.com/e0uzmIO.jpg
https://i.imgur.com/emhOtZx.jpg
https://i.imgur.com/SsY0YBL.jpg
https://i.imgur.com/1QX8rJg.jpg
https://i.imgur.com/G5xjGBt.jpg

Does anyone see any red flags here?

I took the intake off so I could get at the wire carriage that goes to the IACV. It's buried under the intake:
https://i.imgur.com/ZP4YFyM.jpg?1

Anyway, I'm about to start checking the IACV wiring for breaks and other damage. I plan to put this all back together in the next 24 hours. Is there anything I should check while I've got the intake off? Anything in general I should replace to avoid having to take this all apart again? I'm willing to replace the whole plug for the IACV and maybe some of the others too while I have this taken apart. Can I buy the correct plugs at O'Reilly Auto or do I have to get them at Honda?

ezone, to answer one of your earlier questions: it seems the ECM may have been swapped in this car. The unused manual trans IACV has a round, 2-pin connector, presumably w/ 3 wires. The auto IACV has an oblong-shaped 3-pin connector w/ 3 wires. I was looking for a splice from 2 wires to 3 under the intake, but I couldn't find one. I unwrapped all the electric tape and shielding from the wires and it's 3 wires to the IACV plug all the way down. Unless they spliced it way down into the cable tray, and I don't think they did as the cable loom is still intact, I'm guessing the ECM was swapped. I guess I'll go ahead and put the intake back on and try troubleshooting the vacuum connections?

 
Rep Power: 518

I didn't notice anything spectacular.

I DID notice the nipple (labeled "B") for the hose at the center of the injectors goes to atmosphere? There looks like no coverage by the IM gasket....so the hose is irrelevant. It's not a vacuum leak, it's an unfiltered air leak into the big air tube IIRC. Would this be a correct assumption?


I'm not seeing anything. Scrape gasket material off with a razor blade?
I don't think you can buy any of them with money. I have saved every wiring harness ever replaced over the years just so I can steal connector shells and pigtails like that.
So it got an ECM AND the wire harness for an auto trans setup?

What's the part# on your ECM? I'll see if I can run it in the parts catalog.


IAC connector for the MT has only 2 wires according to the wire diagram.

 
Rep Power: 0

I went ahead and scraped the gasket surfaces on both the engine block and manifold and replaced w/ a fresh gasket, torqued back to spec, etc. Then I started putting things back together. Everything seemed to go together fine, but I did notice one oddity concerning the hose "H" connecting the fuel return? to vacuum? (I'm just guessing. I don't know what it's purpose is). This guy:

https://i.imgur.com/axvZgWJ.jpg

I was loosening hose clamps at each junction and checking for cracks. When I took this one off, I saw something shiny inside. Turns out it was part of the hose clamp band sticking through the rubber. Not good. Don't know if this was THE problem, but it's probably not right:

https://i.imgur.com/DklXXVa.jpg
https://i.imgur.com/xjW2n8C.jpg

I took it off and compared to a fresh hose clamp. The one on the left is the one I took off. It's got two little prongs that were stabbing into the hose. Maybe this is why OEM stuff rarely uses these hose clamps.

https://i.imgur.com/C906fJF.jpg

Anyways, I took it off, but there wasn't enough material to cut the bad end and stretch the hose to fit. So, I'll go get a new piece of hose tomorrow and clamp it correctly, then test it. I'm also going to pay a little more attention to burping the coolant this time and do a better job at idle relearn-ing. I need to find a good guide for idle relearn. Suggestions?

---------------------------------------------------------
Took me a minute, but I see what you mean about the B hose vent to atmosphere at the manifold. I see what you're saying: it's not covered by the gasket, so it doesn't see vacuum. It doesn't appear to do anything. I remember when we first got the car nothing was connected to this port. Years later this B hose got hooked up, but that's been years past - I don't remember why. Maybe it really is useless... what's the point of bypassing the air filter w/ this air? I'll look through the manual and see if I can find something.

That's a bummer about the connectors. When I looked at the IACV connector and the others near it, all the wiring looked fine: no breaks, tears, melted plastic or anything. They could still be broken within the connector I guess. I'm more convinced than ever that it's a vacuum leak. I think I need to: fix the bad hose I described above, burp the coolant WELL, and relearn idle correctly. I think I didn't do so well on those last two things when I replaced the IACV in August.

Right, I typo'd what I wrote earlier. Meant to say: 2 wires from ECM to 2-pin connector @ MT IACV, 3 wires to 3-pin connector for AT IACV.

 
Rep Power: 518

Fuel pressure regulator, needs manifold vacuum. Fuel pressure varies with manifold vacuum.

WTF why does it have hose clamps? Should not fit so loose that it needs clamps. Those clamps are way too big for that tiny hose. That can actually pinch the hose to create leaks.
More like the OEM used hose that fits right. There are almost never clamps on the small hoses.

Oh yeah, I already asked about this in post #10.
There is none in your application. I think someone just saw an open port and HAD to connect something to it. If it's not really leading to manifold vacuum, I think you'd be better off removing the hose from that nipple and stuffing a bolt in the hose.

What WOULD that nipple be for? IDK, what's the manifold off of?

Get everything RIGHT before trying this. If the idle is so high it's surging repeatedly, it's not gonna improve with a relearn.

Disconnect battery for 10 minutes or so to erase learned parameters.
Start engine, get it warmed up to operating temp.
Park or neutral.
Turn off all electric loads.
Let it run 10 minutes without any electric loads.
If the radiator fan runs, add that much more time to the 10 minutes.


HTH

 
Rep Power: 0

I went to the auto store and got a couple feet of vacuum hose. I replaced the "H" hose and left hose clamps off both ends.

https://i.imgur.com/68bJFD2.jpg

I started the car and let it run for 10 minutes or so, trying to get the air out of the coolant. I got it up to temperature, but I never saw any bubbles come out. It was idling around 1000 rpm, nice and smooth. I had disconnected the battery during all this though, so the codes were cleared, the MIL went off. Before I shut it off, I tapped the accelerator to see what would happen, and it started slow surging again: 1100 to 2000 rpm or so. So, I guess I'm back to the drawing board.

Here's a picture of a label on the ECM. Is this the number you wanted?

https://i.imgur.com/8WvzUcY.jpg

 
Rep Power: 518

As long as the hose fits tight on the nipples (leak free), there should be no need for additional clamps.
Yep.

ECM# 37820-P2E-A12 looks like it fits 99-00 Civic 2,3,4 door DX CX LX Manual trans

Have you looked into this idea yet?

Does the TPS voltage NOT return to the exact same value after you tap the gas pedal? when the idle starts surging?

How many miles are on this throttle body?

Can you grab the throttle shaft (the wheel where the cable is attached) and 'pull' it 'away from the direction of vacuum' and get the idle to go back to normal?

Got another ECM to try?

I wonder which harness the engine has? Is it for an auto or manual trans?

I wonder which ECM terminals are being used to drive this A/T IAC valve?


Jeez. Makes my head hurt. It's hard enough trying to figure out some problems when the car is all original.....
Now.....Now it's just that much harder.


Too early. No coffee.

 
Rep Power: 0

Not yet. I'll check it out today.
Do I need a scan tool to check this?

No idea.

I'll try this afternoon.

No.

 
Rep Power: 518

A plain voltmeter could suffice. You might Google how to backprobe a connector so you can take readings and watch the action in real time.

 
Rep Power: 0

Quick update: I started it again, jiggled the TB shaft a little. No improvement.

Let me try asking a different question. When I did all this work yesterday, I disconnected the battery, clearing the MIL codes. Since I've gotten everything back together, the MIL has been off. However, while I was playing around, trying to make something happen when it was surging, at some point after it warmed up, the fast idle started. I'm pretty sure the fast idle started as soon as the MIL lit up. It's like one is triggering the other. What could cause that?

Fast idle = it bounces between ~ 1750 and 1800 rpm really fast. If I open the throttle or bump the accelerator, even if I do it hard, it'll immediately jump back down to 1750/1800 rpm really fast. It's like the computer doesn't want it to go away from that narrow window so it forces the idle to stay there. Does that help explain what it's doing?

Have not checked TPS position yet. Need to get scan tool. I don't have a multimeter w/ leads long enough to probe ECM yet.

Also, I tried plugging the underside of the unused MT IACV while surging and nothing happened. This may not mean it's not causing trouble though. The only way to be sure would be to block the ports off entirely w/ an o-ring or something.

 
Rep Power: 518

Which code?Not really. I expect it to go from 2000 to 1200 repeatedly as fuel cut occurs. Staying at that high RPM without surging makes me think TPS or ECT might be inaccurate or reveal a different problem.
I could backprobe right at the TPS connector.

Those were for coolant hoses, there would not be a vacuum leak there. If you want to block it off, remove it from the manifold and cut out a piece of thin cardboard (cereal box) that will cover up both holes, and reattach the valve. That should block both ports if you did it right.

 
Rep Power: 0

Same one as always P0505.

ECT checked fine when I scanned last time. Not experiencing overheating problems either. I will try to test TPS next.

Yep. I forgot. I may try the cardboard thing nex too.

 
Rep Power: 518

Code set criteria:

Monitor begins running 120 sec after startup
ECT must be between temps 177*-212*F
A bunch of other codes must not be present...and a few other details.

Code set @ More than 200 RPM above target speed for more than 20 seconds while TPS voltage indicates closed throttle.

 
Rep Power: 0

Sounds really generic. I guess that explains this wild goose chase

 
Rep Power: 518

That's a lot more info than the generic "P0505: Problem in the idle control system."

 
Rep Power: 0

I finally broke down and took the car to a local mechanic. He wound up replacing everything from the intake to the air filter to match the Y7 setup (it has a Y7 engine). He said someone had swapped this assembly from an EX model onto this car. I was skeptical that this would work, but we've had it for a few days now with no problems. By the way, he found a used assembly to swap onto mine, so it wasn't very expensive. I cannot explain WHY the swapped setup just quit working all of the sudden after all these years I'm just glad the problem seems to be resolved

Final assembly pictures:
https://i.imgur.com/nKCiLQD.jpg
https://i.imgur.com/Ot7Ou4J.jpg
https://i.imgur.com/uYvyyFO.jpg
https://i.imgur.com/gMZrZn4.jpg

 
Rep Power: 518

Yay!