I feel like this car is a never-ending saga of issues. I've never had so many problems with a Honda.
Alright, I'm done venting.

2003 Crv EX M/T AWD
Okay so I was driving down the highway, minding my own. Get off on the off ramp, come to a stoplight, pop in neutral, rpms start revving up and down between 1k-2k. I've experienced this before after replacing the iacv with an aftermarket, but had gotten that solved with a coolant bleed/tb tune. Hasn't done it for a long while though. Engine has been idling around 675, gas mileage has been ****, 15mpg, but at least it'd been idling nicely. Id just replaced my water pump, so I started thinking maybe there was air trapped. Bled coolant again, still surging. Can't seem to get rid of the surge this time. P0505 in the pending, no detectable vac leaks, if I cover the iacv port the car dies almost immediately. After a lot of frustration, I said screw it, and covered the iacv port with some aluminum tape, popped 2 small holes for it to breath, and got the car idling at a nice 750(which I think is where it's supposed to sit?). Now the car idles good, sounds really raspy, but no idle hangs, or surging. However, upon starting the vehicle, I get p0661, which I know is part of the imrc system. If I clear the code with the engine running, and drive, it never pops up. Only on startup. So, what I want to know is, is it possible that this is the root cause of my surging, effectively throwing off the iacv, and the code is only finally popping up because I was able to get the engine running stable enough for the pcm to detect it? OR is the tampered iacv throwing off the vacuum, messing with the voltage to the imrc system? I'm going to try and figure out how to test the imrc solenoid and go from there. But just wanted to see what you guys think. Either way I'm going legit this time and replacing with a Honda oem part. I just want to be super sure before I start throwing money though, because both the solenoid, and the iacv are at least $275 a piece. Really don't want to buy one only to have it be the other.

Thanks in advance!

 

Engine light turned off while driving home last night. Got up early and ran some voltage to the solenoid, it audibly clicks when applied, so I want to say it's good, but I haven't checked it with a multi-meter yet. Light popped back on upon start up. So it's definitely related to startup vacuum.

 

Had no clue our cars had this type of intake. I’ve seen this stuff on newer cars but genuinely expected an 02-04 to have just a straight manifold.

Anyways, maybe you get a code on startup because the rotary valve motor (?) does a sweep from stop-to-stop upon engine startup and maybe something is blocking it which sets the code on startup? Is that even how this works? Lol

But since you dont actually need it to adjust constantly while driving it won’t set during engine operation...? What do you think about that?

Just read an article about the K20 that mentions that the solenoid gets voltage when engine reaches 4700 RPM. Maybe the DTC would set then. This is interesting.

 

To be completely honest, I didn't even know what an imrc was until the code popped up and I started researching. I've never owned a car with anything other than a straight manifold haha.

From my understanding, there's two sets of runners in the manifold? One short, for what I'm assuming is initial acceleration, and then the long runners that open up and the shorts close during higher rpm, highway driving? Idk if I'm interpreting any of it correctly, but I do know that the system consists of the runners themselves, actuated by a diaphragm valve or something, which is vacuumed by the solenoid. There is a position sensor on the runner actuator. So it could either be that one set of runners are sticking, the solenoid isn't releasing the vacuum, or the position sensor isn't giving the correct position.

The code states "Intake manifold tuning control valve circuit low bank 1"

The only test I've come across so far is the applying voltage to the solenoid to see if it clicks, which it did. I still need to find the specs for a multi-meter reading on both the solenoid and the position sensor.

I'm still thinking that possibly my aftermarket iacv is junk and finally crapped out, and is either stuck open or sending the wrong voltage to the ecu, and that because I taped it, essentially locking intake of air on startup, instead of the normal higher intake for warm up, it's throwing off the imrc on start up. Funny thing is even though the car pretty much stays at 750, sometimes it it does still manage to climb to 1000 on warm up before settling at 750, so something is still managing to adjust. I did take off the iacv, there's no carbon build up or anything, I only had just put it in maybe 8 months ago?

Of all the idle surging articles and threads I've read, they always state the same, air in coolant, vacuum leak, or faulty iacv. I haven't seen anything pointing to the imrc causing those types of symptoms. The only symptoms I've seen for the imrc, are engine codes, fuel consumption, noisey flaps that sound like noisey valves, and engine hesitation. All of which, I also have lol.

Honestly, I'm almost ready to grenade this car.
Between this, and still not being able to get rid of the shake, idk if it's even worth it to keep trying. One Honda service department pretty much already told me they weren't willing to look at the car because "it's not factory" which is the most ridiculous thing I've ever heard, but that's pretty much where I'm at right now. It's been almost 3 years of never ending issues.

 

I worked at a CDJR place and the alignment guys worked on the lifted wranglers (with mild lifts nothing too extreme) all the time. And a lift wouldn’t effect the way the engine operates lol... can’t tell you how many lifted Cummins I worked on ugh. That dealer is being lazy.

You seem to have a good understanding of how the intake works.

I was trying to find a diagnostic for the IMRC position sensor on alldata, but as usual it can be tricky finding the correct information. I’m attaching a pinout of the connector, you might actually be able to google it and find a diagnostic procedure for the sensor itself.

 

Key on to check for voltage, key off for resistance.

 

Smackin you are the man!
I got anxious about spending a lot of money on parts. I've already put a bit more money into this car than I'd hoped to, and like a quarter of that is modifications, and I don't feel like putting a ton more in only to be disappointed. I've decided that if this next round of working on the ol girl this weekend doesn't solve a majority of the issues, I'm gonna let her go. Maybe try to find a cheap Tacoma or something(I don't think I'm that lucky, but maybe). So, I made a trip to an auto wrecker that was quite a ways away from where I stay, all the ones near me never have anything. This place had a ton! And a lot of elements too! Let me tell you, ya boy made out like a bandit😁

-Got a pair of oem axles, in really good condition, with the exception of one torn boot. Whatever, easy fix. $60 for the pair, Honda wanted $950 for a pair.
-Got a throttle body with all the oem trimmings, just needs a light cleaning. $40.
-Got the intake manifold with the entire imrc set up, solenoid included. I plan to clean and test everything with the info that you provided before I put all that on.(BIG thank you again Smackin!). $30
-And then just a little something to make myself feel better, I found the oem spoiler(minus the light cover, but that's an easy fix)! I've been looking for one of those since I bought the damn car!! Only $20??? That one was a, I hope I fix the car so I can continue modifying purchase tbh.
I found more useable parts in one day across like 4 different vehicles than I have in the 3 years that I've been going to my locals. For once I'm excited and hopeful.

Total cost $150 and a split eyebrow from catching a box wrench with my face.
I'll take that over the $1500+ I was potentially going to spend on just axles, an iacv, and an imrc solenoid.
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In the event that this doesn't work out, I'm going to have quite a bit of parts for sale, so if anyone is interested in the spoiler or oem axles, I'll gladly let them go for the price I paid😭 plus shipping of course. Lots of other goodies too. But before we get to that point wish me luck

 

Tested the harness, it was fine. Put the new intake on, solenoid, throttle body, new gaskets for both. Still doing the same ****. Tried to bleed the coolant with some specialty funnel, left the car running for like half an hour, fans cycled twice, both upper and lower rad hoses got hot, heater blows hot, eventually started boiling and spitting a ton of coolant out of the funnel. Can't find a vac leak anywhere, I cannot get this damn car to idle properly. I'm over it.

 

That “boiling” in the specialty funnel was most likely air bleeding from the system after the thermostat opened all the way. Don’t think I’ve ever boiled coolant before while bleeding... I think that would be bad lol.

I’m assuming you did the Ohm testing on the new (used) sensor before putting it in?

Still getting code P0661? Assuming all the other procedures were followed correctly above:

I’m just reading out of the book lol. Check for short to ground in the circuit basically. Other steps after this would recommend replacing the ECU (or updating the software - but c’mon that’s prob just a waste of money at the dealer)

 

Verify all air is out of the system. Sometimes this takes a few cycles, air pockets in the system are stubborn and can ruin your day. If you are still getting air maybe have the system pressure checked. I would try to put an oem valve in there. Seems like the issue is related to that valve since you can get it running ok with it plugged I think you stated. What happens if you unhook the IMRC connector?