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Old 08-18-2006, 02:09 PM   #1
Ridge
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Poor gas mileage connected to idle learn procedure

I just thought I'd post this in regards to some people complaining of poor gas mileage. It may have been discussed here before, but I've read alot of the mpg threads and don't recall mention of it. This has been talked about alot on the net recently in regards to the Honda Fit, but these Fit users learned it from a Honda Pilot Forum which brings us to the Ridgeline since it shares the same engine as the Pilot.

Pilot users were complaining of poor mpg, and after performing the "idle learn procedure" they gained like 5 to 7 mpg.

Idle learn procedure from my memory is:

(make sure AC/heat and other accessories or off before step one)

1- disconnect neg batter cable for 5 minutes
2- reconnect neg battery cable
3-start vehicle
4- Let the vehicle idle through two fan cycles, and after the fan shuts down after the second cycle, let it idle for 10 more minutes
5-shut off vehicle and start it back up and punch in your radio code.
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Last edited by Ridge; 08-18-2006 at 02:18 PM.
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Old 08-18-2006, 03:33 PM   #2
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Re: Poor gas mileage connected to idle learn procedure

You may only be able to do this with the aid of the Honda Diagnostic System, ie during a trip to the dealer, but the official Idle Learn Procedure is as follows (verbatim from page 11-266 in the Service Manual):

1. Make sure that all electrical items (A/C, audio, lights, etc) are off.
2. Reset the PCM with the HDS (see above)
3. Turn the ignition switch ON (II) and wait 2 seconds.
4. Start the engine. Hold the engine speed at 3,000rpm without load (in Park or Neutral) until the radiator fan comes on, or until the engine coolant temperature reaches 194F (90C).
5. Let the engine idle for about 5 minutes with the throttle fully closed.

Note: If the radiator fan comes on, so not include it's running time in the 5 minutes.
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Old 08-18-2006, 05:03 PM   #3
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Re: Poor gas mileage connected to idle learn procedure

This is excellent information. Someone who has had bad gas mileage needs to test this theory asap.

I'll be there are thousands of RL's out there that were not properly set up.
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Old 08-18-2006, 08:23 PM   #4
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Thumbs up Re: Poor gas mileage connected to idle learn procedure

Thanks guys. Next trip to the dealer. 5 to 7 more MPG would be great. Getting 16 in summer like clockwork.
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Old 08-18-2006, 11:15 PM   #5
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Re: Poor gas mileage connected to idle learn procedure

Quote:
Originally Posted by Lingered_I
You may only be able to do this with the aid of the Honda Diagnostic System, ie during a trip to the dealer, but the official Idle Learn Procedure is as follows (verbatim from page 11-266 in the Service Manual):

1. Make sure that all electrical items (A/C, audio, lights, etc) are off.
2. Reset the PCM with the HDS (see above)
3. Turn the ignition switch ON (II) and wait 2 seconds.
4. Start the engine. Hold the engine speed at 3,000rpm without load (in Park or Neutral) until the radiator fan comes on, or until the engine coolant temperature reaches 194F (90C).
5. Let the engine idle for about 5 minutes with the throttle fully closed.

Note: If the radiator fan comes on, so not include it's running time in the 5 minutes.
From what I gather in my reading, disconnecting the negative batter cable from the battery will accomplish step 2 Reset the PCM with the HDS so the HDS (Honda diagnostic system) won't be needed.
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Old 08-19-2006, 04:07 AM   #6
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Re: Poor gas mileage connected to idle learn procedure

If this/these are the definitive methods of finessing the "learn idle", how long will it take for me to clumsily "reteach my idle" my bad habits?
I mean... is this procedure going to have a lasting effect on an otherwise smoothly-running system? And how would you know if you actually NEEDED to perform "the procedure"? A reading of rpm @ idle? (I think mine's around 6-700)

Anybody have an explanation as to what this accomplishes and/or how it could go overlooked in the PDI?

I supppose idle does have something to do with gas mileage, and I'd think that some of this involves tricking the puter into delivering a "less rich" mix to the plugs. I'm no engine mechanic (as you can probably tell ), but wouldn't this, then also, involve a timing adjustment?

Alotta questions... I've seen the Pilot owners' comments, but haven't seen if the Fit owners' have found an explanation for the correlation between it (ILP), and MPG.

Thanks Ridge, for the thought-provoking post. Any links to further discussions would be welcome.
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Old 08-19-2006, 04:35 AM   #7
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Re: Poor gas mileage connected to idle learn procedure

This procedure would give the Ridgeline an extra 5 or 6 miles per gallon? That is huge! If this were true I would expect Honda to let us know and call us in to the dealer to have the thing set up right. That mileage increase is something like 20% and that is almost unheard of by a "minor" idle adjustment. If this procedure works (and with no long term ill efffects) it means there was a major blunder made at the assembly plant and Honda should correct it.
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Old 08-19-2006, 06:19 AM   #8
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Re: Poor gas mileage connected to idle learn procedure

If this does work...I would think it would only effect city MPG since there would be a lot of idling???

Very interesting find!
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Old 08-19-2006, 07:37 AM   #9
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Re: Poor gas mileage connected to idle learn procedure

Quote:
Originally Posted by Pug
A reading of rpm @ idle? (I think mine's around 6-700)
If the idle learn procedure was off would the error show on the Tach? If so, what is the correct idle speed setting? Isn't this part of the get ready procedure performed by the dealer? It's listed in my Honda Service History Booklet and was checked off by my dealer as being done by them. Hopefully correctly.

Most of my driving is short trips, less than 2 miles at a time, my gas mileage is around 14.5 with A/C running all the time. On the road, which is done rarely, I've gotten 21.3 mpg. I think my numbers are respectable. So I assume the idle procedure was done and done correctly. Any feelings on this?
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Old 08-19-2006, 10:14 AM   #10
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Re: Poor gas mileage connected to idle learn procedure

Quote:
Originally Posted by Ridge
From what I gather in my reading, disconnecting the negative batter cable from the battery will accomplish step 2 Reset the PCM with the HDS so the HDS (Honda diagnostic system) won't be needed.
I'm not so sure about that because there are dozens of reasons for disconnecting the battery, and it would be surprising to find that the PCM is reset so easily.

The service manual states that the idle procedure be run whenever you replace, reset or update the PCM, or replace/clean the throttle body. No mention of just disconnecting the battery. In sections of the manual that require the battery be disconnected, there is mention of re-entering the radio codes, and re-arming the auto window, but nothing else.

The procedure for diagnosing the idle on your truck, to see if needs to be reset, is as follows:

1. Disconnect the EVAP canister purge valve connector.
2. Connect the HDS (this can probably be skipped)
3. Start the engine and hold the revs at 3000 in Park or Neutral until the radiator fan comes on, then let it idle.
4. Check the idle speed without any load: headlights, blower fan, radiator fan and air conditioner off. It should be 730+/-50.
5. Let the engine idle for 1 minute with high electric load: headlights on main beam, AC set to max cool, blower fan on high. It should still be 730+/-50.
6. Reconnect the EVAP connector.

If the rpm's were out of scope, the learn procedure should be performed.
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Last edited by Lingered_I; 08-19-2006 at 10:16 AM.
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