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Discussion Starter #1
Was just sitting in the drive-thru about to go on a 3-hour trip and I noticed the idle would dip down to about 500 RPMs then recover to a little over a thousand. Then it would settle down at 750 or so again and repeat this process every 5-10 seconds or so. Currently on the highway and all seems fine. No check engine light or anything. What should I be checking first? I'll be limited on tools for a weekend getaway so hopefully it only affects idling.
 

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Well, first you disclose the model, year and current miles...

But in older vans this was an Idle Air Control Valve.
 

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Discussion Starter #3
Well, first you disclose the model, year and current miles...

But in older vans this was an Idle Air Control Valve.
Sorry thought it would have been in my sig. I'm posting from my phone. 2005 ex with 142k miles. Engine muzzled.
 

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Looks like you don't/didn't have a sig configured! :unsure:

Ah, that's better! :giggle: (u reminded me to update my sig!)
 

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Discussion Starter #6
Sorry, EX-L. I certainly have a VCM motor. From what I have researched so far, the IAC valve is typically to blame for this as someone already mentioned. It actually went away the rest of the trip and idled fine.

What I couldn't find was a replacement part for 3rd gen 2005 and up. On RockAuto it drops from the menu after 2004. Is it not available as an aftermarket part for 2005 and up? Besides the replacement part, it looks like it can be cleaned as well.
 

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We have the same problem with our 2005 EXl at195K. We changed the spark plugs which had about 70-80K on them. It helped very little, but not enough. We bought an ODBII scanner and saw that the fuel trim on one of the banks. I think STFT1 was always high during idle and at high RPMs, but not during loads like acceleration or uphill. We did a quick visual of any leak from hoses but did not see anything. The top recommendation was to check for a vacuum leak but to find a vacuum leak to us seems to be very difficult and complex to do. We even look at vacuum leak smoke machines, but this seems to be very difficult. Does anyone know the typical cost of finding a vacuum leak? Another suggestion was to replace the MAF. We hesitated on that since it is like throwing parts at the problem without knowing. We gave up, live with it and the problem seems to occur less. We would love to know the fix for this as well. Hopefully, some tips to help you on your journey to resolve the issue. Thanks
 

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Discussion Starter #8
I'm confused to whether the 05 and up models even have a replaceable IAC valve. The part disappears from all parts sites once you surpass 2004. Plenty of youtube videos online with people cleaning their IAC on 99-04 models. Can I just follow the same procedure? It's a very similar engine right?
 

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Through Throttle body cleaning and adaptation with a bi directional scanner..

Also no vacuum leak. A smoke test?
 

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Yeah, seems no IAC valve on 2005 and up. So basically a throttle body cleaning and check for vacuum leaks.
Mine had this same issue before I went on a trip last year. I cleaned my sensor and the throttle body and put a new paper gasket on that is between the intake plenum the throttle body. Missed my appointment for honda idle relearn and all that but, it was actually fine after that. Also my oxygen sensors may need to be replaced.

Sent from my SM-N976V using Tapatalk
 

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Discussion Starter #12
Mine had this same issue before I went on a trip last year. I cleaned my sensor and the throttle body and put a new paper gasket on that is between the intake plenum the throttle body. Missed my appointment for honda idle relearn and all that but, it was actually fine after that. Also my oxygen sensors may need to be replaced.

Sent from my SM-N976V using Tapatalk
What sensor? MAF? I have some throttle cleaner coming in the mail today. I'm starting with that.
 

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OP: Observation. Started while sitting at a Drive-thru. 750 rpms, seems normal. Was van in park/neutral? Was AC on? A/C kicks on, rpm increases? Foot on brake? Turning steering wheel? (power steering sensor kicks in, rpm goes up)......just thinking out loud......What would cause idle speed to fluctuate. BUT now it's gone!

Just out of curiosity. Go back to same drive in, try and repeat everything the same, (time of day/temp), and see if you
can repeat the idle issue.......

Or, just relax, and enjoy life...... :)
 

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Discussion Starter #14
No AC or anything weird. Car was warmed up, sitting still in drive thru with foot on brake pedal. It was clearly surging in some facet. I cleaned the throttle body pretty good today. At least as good as you can clean it while it's still attached. Still running okay since that day. I'll keep an eye on it.
 

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We have the same problem with our 2005 EXl at195K. We changed the spark plugs which had about 70-80K on them. It helped very little, but not enough. We bought an ODBII scanner and saw that the fuel trim on one of the banks. I think STFT1 was always high during idle and at high RPMs, but not during loads like acceleration or uphill. We did a quick visual of any leak from hoses but did not see anything. The top recommendation was to check for a vacuum leak but to find a vacuum leak to us seems to be very difficult and complex to do. We even look at vacuum leak smoke machines, but this seems to be very difficult. Does anyone know the typical cost of finding a vacuum leak? Another suggestion was to replace the MAF. We hesitated on that since it is like throwing parts at the problem without knowing. We gave up, live with it and the problem seems to occur less. We would love to know the fix for this as well. Hopefully, some tips to help you on your journey to resolve the issue. Thanks
Correction. The hight STFT1 does not cause our low RPM issue. We found a small clamp that was not clamped onto the hose and the intake where the hose is plugged into. I am pretty sure, but not 100% that is what helped our RPM drop issue. Although, the hose seems to be very tight without the clamp.

An additional observation is that the adjustment of the VCMtuner seems to impact the high value on the STFT1. When we tune the VCMtuner lower, the VCM kicks in and the STFT1 is lower. We then increase the setting on the VCMtuner, the VCM is disabled and the STFT1 is higher.

We bought the Throttle Body and Air-Intake Cleaner but did not have a chance to do this work. We also bought a gallon of Sea Foam in case this will fix the problem, but did not even use it. I think you might want to look at the vacuum leak first.
 

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This may sound dumb, but my daughter's Odyssey had the same issue and had the lean bank code. Turned out to be low coolant.
 

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Discussion Starter #17
Drain and filled my Rad last summer along with replacing the thermostat. Coolant level is fine and overflow tank has plenty in it as well.
 

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Discussion Starter #19
To the best of my ability yes. The duct from the air box had some micro cracking but it was very light. I did end up cleaning the throttle body and issue hasn't resurfaced since the first instance. I'm simply keeping an eye on it at this point.
 
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