Started the car after doing repairs on the car and it idles at 3000-3600 rpm. Don't know why. 2000 Honda Accord, 2.3L Vtec Engine. The high idle rpms made me nervous, so I did not run it for more than 2-10 seconds at a time. Started it perhaps 5 times.

I did three repairs. The big repair, I replaced a leaking water pump - while in there, replaced the three engine seals (camshaft, balancer shaft, crankshaft), the gasket behind the balancer gear case, the two tensioners, and the timing belts. Had to drain the coolant to do the water pump repair. The second repair was I replaced the O-ring on the Vtec Solenoid Sensor. The third repair is I replaced a leaking 4-6 inch hose (5/16" inner diameter) that goes into the Idle Air Control Valve (IACV). It carries anti-freeze into the IACV. Decided to do it now since I had already drained the coolant to replace the water pump.

How do I fix the high idle? Is the problem that antifreeze has not yet made its way into the IACV? Do I just let the motor run at 3000-3600 rpms until coolant has reached everywhere in the motor, and the problem will then just go away? Or something else.

 

The 4-6 inch 5/16" coolant hose I replaced - I checked a parts diagram. It goes into the bottom of the throttle assembly. I don't see an IACV in the parts diagram. Is the IACV part of the throttle assembly? Or it has been superceded with something else. I am not sure yet.

Regardless, I still have the (greatly) excessive idle speed on startup. Cannot drive the car, cannot put it into drive with rpms that high w/o risking the transmission. Any ideas would be helpful.

 

Your Honda Accord has an IACV, but I don't know where Honda put it, but it should be mounted to the intake system at some spot. Probably harder to get to than the older ones. Just nature of automobile engine layout.

You should read the other idle thread where the guy just fixed his idle problem. He had also done maintenance, but had left a vacuum link that was causing surging idle.

Find your IACV and unplug the electrical plug on it while the idle is surging. If the idle continues to surge, or surges even higher, you likely have a gap, or vacuum leak in your intake. If unplugging the IACV causes the idle to settle down to a very low idle but still running, or if the engine shuts off, your IACV is not working right, and is causing the surging idle, and should be checked.

https://honda-tech.com/forums/honda-...dling-3341461/

 

Thanks, appreciate the input.
I have been reading other threads. I don't think there was anything wrong with my water pump/timing belt work. If I was off a tooth, the engine probably would not run at all. And there is nothing there that, it seems to me, would cause an idle problem. So based on what other people have written, I have narrowed it down to the IACV and the Fast Idle Thermal Valve (FITV). It could also be that the sensor on the VTEC Solenoid died when I disconnected it, took it off, and replaced the O-ring - but I think the probability of this happening is really low - the battery was disconnected, so no hot-plugging took place. I have found some good writ-eups on the IACV and the FITV - hopefully cleaning these and replacing old rubber gaskets will take care of it. I am thinking I dislodged a small piece of sludge when I replaced a leaking 5/16" diameter coolant line and it got into something that is supposed to move and is preventing it from operating properly.

 

Since you had the coolant out of the block, be sure to make sure you didn't leave air in the system when refilling it. Air in there will cause an erratic idle because of the lack of continuous coolant flow past the IACV.

 

Well noted. It is a good point. That said, I have not found a post saying they got 3000-3800 rpms (like I am getting) because of an 'air in a coolant line' problem. Their rpms were more like 1500-2000.

I took off the IACV - actually took off the intake manifold cover; the IACV is attached to it. Cleaned the IACV, replaced the two coolant hoses and the vacuum tube that go to it. The hoses & tube were getting pretty hard, and they were stuck on. No way I could have gotten the hoses off while behind the intake manifold cover and between the cover and the firewall. Also replaced the 3-ring gasket that is part of the IACV. I am still waiting for a custom vacuum hose from the local Honda dealer that goes in front of the IM cover (the ends have two different sizes; I had to cut this hose to get the IM cover off). Everything else is put back together so I am just waiting for that.

There was air in the coolant hose going to the straight pipe on the bottom of the throttle body (TB). So that might have been part of the problem. Maybe the entire problem. Nevertheless, though extra work, I know I now have a clean set of hoses and a fresh gasket - that are not old, hard, brittle, and so on. If the IACV did not die and is still working, these new parts can only improve the integrity of the motor - for a modest cost in time & money. We'd like to keep this car for awhile.

This coming Wed or Th, the part should be in. Put that part on and finish reconnecting the stuff above it (OCV Valve and throttle cables), make sure engine is full of coolant, cross my fingers and then start it again, see what happens.

 

Recheck your vacuum hoses.
Not all that familiar with 98-02s, on the 90-97s there are a few vacuum lines I normally detach for more room. There are a few spots that are also capped off vacuum lines.
If the hoses were removed/disturbed/damaged or the caps were accidetnally knocked off, you would have a false air leak which would cause the engine to rev on its own.
Also recheck your throttle cable routing and tension, as well as the C-C tension, verify the TB itself is fully closed.

 

Got it fixed. Posting this update for others who might have a similar problem. Thanks to the posters to this thread (and others with related problems) because you all helped me get this fixed. Honestly, don't know for sure where the problem was or what fixed it. I will state what I did. What of these things solved the problem, or where the problem was exactly, I don't know.

After reading a lot of posts on this (and other) forums, it seemed to me the problem was most likely either (a) a vacuum leak problem somewhere, air getting into the throttle body and causing the motor to run fast, or (b) the Idle Air Control Valve (IACV) was not functioning properly. I decided to remove and clean the IACV, see if this helped. By doing this, I knew I would likely fix some vacuum problems too.

I decided to take off the intake manifold cover (or a plenum, I guess, it is called). Why? The IACV is on the back side of the plenum and facing the firewall. This makes it difficult to access the two bolts holding it on and the three hoses (two coolant, one vacuum) that run into the IACV. While I knew I could get the bolts off, I was not so sure about the three hoses. And I did not like the idea of reattaching the IACV blind, with a new gasket on it. I felt I needed to see and make sure the gasket did not get pinched, or fall out of place while reattaching the IACV. Some posters talked about taking the IACV off and cleaning it without removing the plenum, but this was not realistic in my case, especially with 19-year old hoses that were glued onto the IACV and were pretty hard and not flexible any more.

So here is what I basically did.
Removal:
1. With the aim of removing the intake manifold cover or plenum, I began by removing the air intake hose from the air cleaner to the throttle body.
2. Removed the two throttle wires - from gas pedal, and from cruise control - attached to the throttle, then unbolted the throttle wire holder from the plenum.
3. I then disconnected the three electrical connectors plug into parts attached to the plenum.
4. I removed the four vacuum hoses that go to various parts attached to the plenum - brake booster, PCV, IACV, and another going to the purge control solenoid. The solenoid one would not come off, so I cut the hose.
5. Unbolted the holder for the temperature sensor and the ground wire next to it.
6. Unbolted the holder for the purge control solenoid (front side of the plenum).
7. Raised the front of the car, put on jack stands.
8. Drained the coolant from the motor.
9. Removed from the throttle body (TB) the coolant hose that goes into it from the motor (next to the thermostat).
10. Went under the car, removed the oil filter (to access the coolant hose that goes to the IACV).
11. While under the car, removed the 'IACV to motor' coolant hose at the motor side. Hose would not come off, so I ended up cutting the hose
11. Unbolted the plenum nuts (2) and bolts (3) and removed it with the IACV attached to it.

Cleaning and new Parts
a. Got some carburetor cleaner and with it and a couple scrapers, cleaned the carbon out of the plenum. There were places that had significant carbon buildup.
b. Removed the IACV from the plenum. It did not appear very dirty, certainly not all carboned up. Cleaned it and it looked much better.
c. Obtained an IACV gasket from the Honda Dealer. The old gasket was not cracked or super brittle, it still had some flex though 19 years old.
d. Carefully cleaned both the surface of the plenum and the IACV using a razor blade and 400 grit emory cloth - to ensure a smooth fit; then reinstalled the IACV onto the plenum, with the new gasket.
e. Bought (from the Honda Dealer) the two coolant hoses that attach to the IACV. I wanted to ensure a good fit. A little pricey, but peace of mind.
f. Got vacuum hose from local NAPA store, for replacing the vacuum hose that attaches to the IACV. This bulk (or stock) hose fit just fine.
g. Bought a new vacuum hose (from the Honda Dealer) that attaches the plenum to the purge control solenoid. The ends are different sizes - could not use stock vacuum hose.
h. Bought a new gasket for between the intake manifold and its cover (its plenum).
i. Carefully cleaned the rim of the plenum (where the gasket would sit) and the rim of the intake manifold (where the gasket would sit).
j. With a utility knife, cut, from the underside of the motor, the piece of coolant hose remaining on the motor in order to remove it. This is the hose that goes to the IACV, remaining after cut the hose.
k. With the utility knife, also cut or slit the coolant hoses (parallel to the pipes) attached to the IACV since they would not come off.
l. Also cut off the piece of vacuum tube (that went to the purge control solenoid) still remaining on the plenum (the pipe into the plenum).

I think that is everything. Then I put everything back together - slowly and carefully.

Then I crossed my fingers and started the motor. It was good. Not sure what of the above fixed the problem, but the problem went away.
Was I mad that I had to spend more time working on my car? Yes. But I also know that hard and old hoses and gaskets have been replaced, improving the integrity of the engine.

 

What’s the purpose of that vacuum hose that goes to the iacv? On dx models it doesn’t exist.

 

Where is it located?

 

goes from the intake manifold above the injectors to the iacv.

 

Off the top of my head, you may be thinking of the Fuel Injection Air(FIA) Control System that is used on VTEC engines.
Not sure if DX(non-VTEC) engines don't have the IAR control system, which is the resonator controls for the air intake or if there is the Intake Air Bypass Control Valve(IABCV).

 

There are two IACV units for the 2000 Accord 2.3L engine. On PartsGeek.com, one PN is 5983-05447042 (only two lines coming in, so I assume the coolant in and coolant out ports), and the other PN is 5983-05446980, which has the third line (the vacuum line).

I do not know the purpose of the vacuum line. I could speculate, but the honest answer is I don't know.

 

what’s your speculation?😊

 

Hello Buffalo Rider,.. you have given a lot of detail, and have done the work yourself,.. but I am not a mechanic,.. but have listed my symptoms and the work done to date by mechanics,.. but mechanics have had to disable (by unplugging) the IACV.

Vacuum and air n Coolant, was released/checked,.. but I am now at a loss,. as to: if unplugging the IACV does any damage to the engine, except maybe use too much fuel,..?
Your list was great, impeccable,
Tx,