2.9 High Idle

HondaEater · Oct 31, 2011

My 2.9 is idling at 1500 rpms, I checked the throttle cable and throttle body, I took the iac off and cleaned it with bg intake and throttle cleaner, I've checked for vacuum hoses leaking/cracked, I don't see anything out of the ordinary, someone point me in the right direction?

I also unplugged the tps, the idle shot up higher.

jhammel85 · Nov 1, 2011

Outside of a vac line being bad, I would suspect the IAC.

With it off of the upper intake, have someone turn the key on (engine off!) and see if that plunger inside moves. It should move twice. Mine only moved once and was pretty much worn out. I bought a new one and all was well....This was after I cleaned it too. The solenoid was bad.

straycat · Nov 1, 2011

HondaEater said:
My 2.9 is idling at 1500 rpms, I checked the throttle cable and throttle body, I took the iac off and cleaned it with bg intake and throttle cleaner, I've checked for vacuum hoses leaking/cracked, I don't see anything out of the ordinary, someone point me in the right direction?

I also unplugged the tps, the idle shot up higher.

Ok, what Hondas are you eating up with that 2.9?? lol

adsm08 · Nov 1, 2011

Didja get them heads I sent?

I would wager an IAC as well. With the engine running, unplug it, if the engine doesn't start loping badly or die outright, you have a problem with the IAC.

HondaEater · Nov 2, 2011

adsm08, i did get the heads (thank you), and that longblock. suprisingly, one of the heads off of that longblock were cracked, but within the 4 heads i found two goods ones, so theyre getting rebuilt at the machine shop right now

im debating getting that bottom end rebuilt or not, i've never done an ohv motor before, kinda iffy about doing the rings, main, rod, and camshaft bearings myself..

as for the high idle, thanks for the input everyone, ill be sure to check that IAC motor out asap and get back to you. thanks again!

036speed · Nov 25, 2011

Was it your IAC?

I am idling at 1500 rpms too. I hit this mud puddle a few months ago that i did not want to do (the park doesnt let you off the trail). I made it with out getting stuck but i sucked in my air filter and a bit of muddy water. I am going to try and clean my IAC and see if that helps. I have checked for vacuum as well. Dont see any issues there.

Jspafford · Nov 25, 2011

A coolant temp sensor with a wacky reading will also cause it to idle high. It's been a few years back since mine went out....do you have any other issues? Bad mileage, hard starting?

036speed · Nov 26, 2011

Jspafford said:
A coolant temp sensor with a wacky reading will also cause it to idle high. It's been a few years back since mine went out....do you have any other issues? Bad mileage, hard starting?

I have hard starting as well once warm... And i know my water pump is leaking so i hope it started better after replacing the pump and having my coolant level where it needs to be.

Not sure on the mileage as this truck doesn't see the road

Also, what are you guys idling at?

Jspafford · Nov 26, 2011

036speed said:
I have hard starting as well once warm... And i know my water pump is leaking so i hope it started better after replacing the pump and having my coolant level where it needs to be.

Not sure on the mileage as this truck doesn't see the road

Also, what are you guys idling at?

Coolant temp sensor is super easy to change and IIRC around $15 to get a good one. I say good one because I replaced two in as many years. The first one I got the whole thing was made of plastic. It failed and left me stranded. Was fine if I shut it off and let it sit at least an hour or two, but if I tried to restart it after shutting it off and before it cooled completely done, it would not start.

The second new sensor I got from NAPA and it was plastic on the top connector part and brass on the bottom threaded part that sees the hot coolant.

Mine idles around 850. The RPM needle is at the 9 o'clock position and completely horizontal when idling after warmed up.

036speed · Nov 28, 2011

So i just replaced my worn water pump and cleaned my IAC. My RPMs dropped to 1050 rpms. I can get it down to 850 if i tap on the IAC. I think the last mud pit i hit killed it. Maybe.
I am going to pick up more coolant (i didnt have enough to refill it) and grab a new sensor tomorrow. Hopefully that will bring be down enough to go wheelin this weekend.

Thank you for your help so far Jspafford

kimcrwbr1 · Nov 29, 2011

Replace any hard or cracked vacuum lines and how old is the PCV. I always put a new PCV in with plugs it is the single most neglected (overlooked) part of prevenative maint. A $6 part that can cost hundreds in fuel consumption. If you pull it out of the grommet put a new one in it cannot be cleaned.

jhammel85 · Nov 29, 2011

036speed said:
So i just replaced my worn water pump and cleaned my IAC. My RPMs dropped to 1050 rpms. I can get it down to 850 if i tap on the IAC. I think the last mud pit i hit killed it. Maybe.
I am going to pick up more coolant (i didnt have enough to refill it) and grab a new sensor tomorrow. Hopefully that will bring be down enough to go wheelin this weekend.

Thank you for your help so far Jspafford

Take the IAC off and clean it out with some TB cleaner. It'll work like a champ without you replacing it. Those things are expensive!

036speed · Nov 29, 2011

jhammel85 said:
Take the IAC off and clean it out with some TB cleaner. It'll work like a champ without you replacing it. Those things are expensive!

Yeah, i cleaned it once with some TB cleaner. Brought it down to 1000. Might try again. I can get an IAC from the local junk yard for $8.

And replace the PCV is the first thing i replaced since mine popped out and got full of debris.

jhammel85 · Nov 29, 2011

OK, I guess I missed that.
8 bucks is a steal! I would go for it..

Oh and I just checked out your build! Great work man. I wish I had the guts to do that to mine but for now, it's just a DD and occasional off roader.

036speed · Nov 29, 2011

jhammel85 said:
OK, I guess I missed that.
8 bucks is a steal! I would go for it..

Oh and I just checked out your build! Great work man. I wish I had the guts to do that to mine but for now, it's just a DD and occasional off roader.

Yeah, with a 10mm socket and 30 seconds I can pull one off of a cleanish 2wd 2.9L. And if that one doesnt work they let you swap it.

Thanks man. As you saw, mine started out as a DD too. Then i went wheelin once. Then i got stuck. Then i got bigger tires. And got stuck. Then i started chopping and fabing away and now its a trailer queen haha

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