So I replaced the IACV on my 03 TL-S because it would randomly try and idle at 2k - 3k rpm. First day after the new IACV was fine but now its doing it again. Could it possibly be the throttle body gasket? This throttle body has been taken off 3-4 times and has used the same gasket today.... could air leaking in around this gasket cause this?

 

sorry not 3-4 times TODAY.... idk how that ended up in there.

 

Sounds like a vac leak then. Put your hand around the seam and see if the idle stabilizes, or spray carb cleaner.

 

eh, hard to do as it's intermittent.... Any ideas where to look? The lines around the IACV or just check everything? I already have a new gasket, I'm guessing it wouldn't hurt to put it on huh

 

Take some carb cleaner and spray it around the TB gasket with the car running (with issue if possible) and see if the idle changes. If it does you have a vac leak. Being that the TB gasket is a paper material you really shouldnt reuse it, you should replace every time you take the TB off.

 

what would you guys recommend for getting the old gasket off?

 

Putty knife, razor blade

 

just don't scratch the metal with razor or you create a leak!
some `spray on gasket remover` if its really on there

as soon as I started to read this thread I thought, you didn't replace the TB spacer gaskets? one on each side of spacer iirc
a product called gasket cinch is helpful holding flimsy gaskets and creating seal, with removal possible if needed later in life
I use that stuff on everything, even the bolts on motorcycle engine get a dab

 

did you use an OEM or aftermarket IACV when replacing it? Had this same problem with mine. cleaned the old IACV and the TB gasket with carb cleaner and didn't work at first. Then I used an aftermarket IACV replacement. Worked fine for a few days then it started making popping sounds and still erratic idle. Swapped an OEM one in and problem solved. But it could also be a vac leak like they said so I'd check for that as well and go from there.

 

aftermarket with lifetime warranty..... but if it end up being the iacv will get oem....

 

Check to make sure your cruise control throttle line isn't pulling on the butterfly. as dumb as it sounds my idle issue was solved by disconnecting the cruise control line.

 

Can't recall offhand but doesn't the IACV have coolant lines connected to it..? If so you may have an air pocket trapped

 

Well actually, I had my trans rebuilt a couple months ago and the mech installed an ATF cooler in place of the warmer on top of the trans which had a line going from the IACV to the warmer; As the cooler doesn't need this line he just capped it off at the iacv; the incoming line is still there as normal.....

 

Also couldn't hear or find ANY vacuum leaks, and as I said before this is intermittent, sometimes it runs great, sometimes 20 miles down the road it goes to crap. Sometimes not. Sometimes I can floor the throttle for a few seconds and the problem is gone. I'm about to pull out my hair with this.

 

Anyone?

 

Might want to try an oem iacv.

 

Since you mentioned transmission and cooler, there's a main ground for the ECU and IACV on the thermostat, check it for broken wires, corrosion or loose bolt.

 

Next time you get it, try to push back on the butterflies of the throttle body. Your problem sounds 99.9 the same as mine and nobody could figure it out. It was none of the normal culprits it could be the clamp sticking open a lil

 

I wondered about that too, They both move, the first one closest to the filter end is kinda hard to push but not too bad, both have been cleaned very very well.... What do you mean clamp? And yea I know I should have gotten an oem, but thing is I've taken one off a parts car I have that I KNOW worked great and still the same problem. The past two days the car drove fine then suddenly today problem came back and disappeared again. Just don't wanna waste $150 when I really don't think it's the problem. Can a leak in the intake manifold cause it to idle high?

 

Gonna check those grounds today, had no idea they were there and i'm pretty familiar with this engine.

 

So what does he mean by "clamps" ?

 

the throttle body plate inside is what he meant. make sure its not staying open, sometimes gets gunked up leaves it slightly open. my ground is on the thermostat for my year, this weekend going to run an extra cable from the body to those grounds as well just to make sure, i'm still having idle issues as well.

 

Yea I've cleaned that throttle plate extremely well, even took some 000 fine steel wool and polished the inside of it smooth, and yea my wifes 05 TL had some issues with ground so I did the same thing to it. Mine is an 03 Type S and it has a ground that attaches to the body right behind the drivers headlight I even upgraded it to huge 00 AWG wire for power and ground. I'm still frustrated with this idle issue though, it's not happening as often now but it's still happening. The reason I was asking about a leak in the intake manifold is I removed the upper half of it recently and cleaned it. I reused the same metal gaskets that were on it, so if it has a leak somewhere could that cause the idle to go up? Would basically be the same as the throttle plate being partially open right?

 

And yea I didn't pay attention in your post about the extra cable. Think I'll try that as well let me know how yours turns out.

 

I could be wrong but I am not sure using the steel wool is a great idea- the throttle body has a coating on it. You are only supposed to use throttle body cleaner and a soft cloth.

 

yea I know that but after 191,000 miles and tons of carbon build up it was done for already. and the steel wool I used isn't like an SOS or Brillo pad, it's ULTRA fine, it feels just like a microfiber cloth just does better at getting the gunk off.

 

And as a former employee of Honda of America I can say the only thing you hurt by removing that is MAYBE it's ability to not have so much build up stick to it.....

 

So, almost two moonths later new Honda IACV and i'm STILL HAVING THIS PROBLEM!!!!?!?!?!?!?!?!?! Anyone have any luck? mcottrell95 ?????

 

Without seeing how your mechanic re-plumbed the coolant line, it sounds to me like that's the problem. Coolant has to flow through that auxiliary iac or whatever they call it. Also, blow through it with compressed air; if it's clogged, it could also cause your symptom.

 

Yeah, as TLer trash previously mentioned. If the idle was normal prior to this work, then recheck all the possible things within that particular area. If ya already replaced the gaskets and there's no apparent vac leaks, it's gotta be something simply overlooked.

So there's no CEL codes ? Does the problem occur more when motor's warm or cold ?

 

Try looking at the throttle lines while it is acting up. My similar problem had to do with the butterfly the line attaches to sticking.

 

When he removed the ATF warmer the coolant lines went from the engine to the IACV to the warmer then back to the block. He left the line going to the IACV but capped off the one leaving it and the place where it returns to the engine. Should I run a line from the IACV back to the engine so it has a flowing coolant loop? It seems to act up if its been sitting at idle for a while..... would make sense.

 

Sounds like air in the coolant system if he added a tyranny cooler. Just burp the coolant system.

 

Yea he added a cooler but didn't route the coolant line going from the IACV back to the engine, just capped them off. I think the IACV need FLOWING coolant to stay working properly. And the coolant has been burped several times now....

 

Do this, and blow compressed air through the iac. That coolant passage plugs up easily.

 

Wow, thank you.
This was exactly my problem. Replaced my iac valve (oem) and soon afterwards I had the erratic idle. It was also hesitating at slow speeds, and when idling at a light.

Dealt with it for a few months. Tried to find a leak, burped the coolant multiple times. Nothing worked, figured I had replaced the iac for no reason or got a bad part. Checked my cruise control cable and sure enough I had left it too tight..
Op did you try and just unhook your cc cable to a least rule that out?

 

The TB does NOT need coolant flowing thru it to operate properly. I havent had a coolant line hooked up in almost 500k miles (as have others disconnected it)

The bigger question is, is if he ran coolant to it but there is no way to recirculate it out, where is the other line normally going there going? A trans "cooler" as you state doesnt use radiator fluid to cool, it is simply to warm to do any good and wouldnt cool. If its something in the same place its still a warmer. Also, The old trans warmer didnt have a line going to the TB either. One went to the cross over pipe that the thermostat is on, the other goes to the pipe that runs under the intake manifold that comes off of the water pump.
By chance has the intake manifold itself been taken off? or the top cover removed? There is a metal gasket under it that fits both ways, but only works one way and will cause issues like this too.

 

Good idea to check that coolant, it has been taken off but it was doing that before I ever unbolted it. I hooked a hose up to the capped ports and haven't had a problem since soooo, I guess your lucky because idk why Honda would put a coolant loop to it if it didn't need it. And yea, I know the trans cooler doesn't use coolant it circulates trans fluid through a small radiator at the front of the car using the spot where the former ATF warmer was to tap into the ATF. Only problem I have now is the fact that they used the return "B1" the little one of the two metal pipes, thing is they cut off the ends of it while doing the rebuild so cant use it now, only opition I have is the bigger one that used to be for the ATF cooler, heres the thing, i'd need a hose that's small at one end and large at the other...... Is there even a hose made like that?

 

And cc cable is fine.

 

And coolant doesn't go through the throttle body, it goes through the IACV.