Fast Idle (not surge) 2003 Honda Odyssey

[John Sherman]

Hello everyone, new to the ETCG site but have viewed his youtube posts quite frequently

The situation with my 2003 Honda Odyssey (171K) is that my idle continues to go up (2000 – 4000 rpm without touching the gas peddle) as the engine heats up, whether its hot out or not. Notice it quite prominently in the summer months, not at all in winter when its cold (I live in Dayton, OH). Once we get the engine temp up and have been driving a while, I cleaned the IAC valve in summer of 2014. It didn’t seem to fix the problem as I still had high idle problems when the car was hot (normal operating temperature – no overheating – no CEL, water temp on dashboard reading normal ) and it was hot outside. I didn’t experience the symptom much as I didn’t drive the vehicle much in those conditions this past summer (2014). This is my wife’s vehicle and we don’t travel in it as much as we used to – the kids are grown and out of the house.

I finally went ahead and replaced the IAC valve in early April 2015 after my daughter experiencing the same issue with the high idle. I had cleaned the old IAC with brake cleaner and acetone last summer. There wasn’t a lot of dirt that I could see but by the time it was put back in the car last summer, it was CLEAN. My daughter used the car this spring (early April) and had the same problem as last summer. The engine idle rose to 3000 – 4000 rpm when the car was running, making it difficult to control even with the brakes on full power. This occurs in situations where there is little movement of the vehicle (around town, stop and go traffic, etc….) rather than when the car is going 60 mph on the freeway. It seems to occur when there is little air flow accross the radiator.

Removing the old IAC and replacing with a new one was very straight forward and simple. After replacement, this past weekend April 9, 2015), it was maybe 60 degrees during the day. We went to visit my daughter at college about 45 minutes (University of Cincinnati) away from where we live, and the same situation occurred after installing a brand new part in the vehicle.

I’ve seen prior posts about removing the cruise control cable to solve the problem and that will be my next step but cant’ figure out a couple of things:

1. What does cruise control have to do with engine idle speed, especially since the cruise control should be not functioning the moment I touch the brakes? And believe me, its everything I can do to keep the car under control with the brakes on full blast.

2. It seems that the situation occurs during low speed situations with the engine fully hot (no lights on the dash or the engine temp monitor shows normal). Maybe the hoses going to the IAC off the radiator are collapsing and preventing coolant from flowing through the IAC?

The car is now becoming a safety issue as I cannot have my wife or kids driving the car in this condition.

BTW I’m fairly good with a wrench and cleaned the EGR ports out a couple of years ago, cleaned the throttle body, My issue is NOT idle surge but a continual 3000 – 4000 engine idle speed once the engine is up to temp and having run for a while. I searched the ETCG forums for similiar issues but could not find any responses. I did read ETCG’s posting on engine surging but that is not what I have. BTW, I am also a member of Odyforum but all other posts there point back to the IACV.

For reference, here is a video on youtube which shows exactly whats going in with my vehicle except my situation is more extreme:

Any additional insight would be appreciated.

John in Dayton, OH

Topic

[zero]

Maybe go for a drive to duplicate the issue and check if the throttle body is physically open at idle. If so try removing the cruise cable safely and try to duplicate the issue again. If that does nothing you could check for a vacuum leak, also the fact that you replaced the IAC valve does not mean that it is functioning properly. Did you plug every vacuum hose and plug back in? Are you sure?

Part failures, especially electronic parts, tend to fail in patterns so if there are forums saying that x issue is caused by x part, that’s usually a good place to start trying to solve the problem. By ruling out the usual suspects.

If the throttle valve is getting stuck open there should be a bit of free play in the gas pedal. And please only use throttle body cleaner on intake components, other chemicals may react badly with the seals.

[Tyler]

To the OP, I don’t know if you fixed this or not. I’m assuming you did. But for anyone that doesn’t know. If you have checked the IAC and it’s still happening. This would be your next step to check.

“As another example, Honda engines (I believe 1996 and later) feature a FITV (Fast Idle Thermo Valve) that’s located directly under the throttle body. This valve is prone to sticking. If the plunger is backed out too far, this can affect a vacuum leak, causing a high idle after the engine has warmed to operating temperature. This can also result in a pulsating/fluctuating engine speed. While most repair manuals recommend replacing this valve assembly, it can be removed and cleaned. It’s not uncommon for an IAC to be blamed for an FITV issue.”

[T]

Wow, just ran across this. I have the exact same issue. Did you ever come across the solution?

[Author]

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