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Discussion Starter #1
Hello All:

I've been battling Honda on a very annoying transmission/drive-train "trait" that makes is almost impossible "for me" to drive the vehicle because it's very annoying once you are conscious of what's happening. If you notice you have the same problem after reading this...sorry!

2007 Touring. Had all software updates and torque converter replaced. Bought new, problem recognized at about 40,000 miles, now 78,000 miles, wifes van.

Here's what happens - Driving down the road at 65 mph, top gear, if I crest a small hill and head down the back side, still applying light throttle, I will get a THUD in the transmission/drive-train that can be felt by all passengers. Not a shift, nor does the rpm change. This happens EVERY time I have to ease up on the gas to keep a constant speed, but it seems to be most prevent when going down a slight grade/hill.

Not that this is related, but at the same time the thud happens, my instant fuel economy goes from 35+ mpg (remember, going down a slight grade) to 14-16 mpg, holds for a few seconds, then starts to ramp back up after yet another THUD. In some cases, I have gone down a large grade with slight throttle and the instant mpg holds at 14, then when I go up another subsequent incline the instant mpg will rise (20-22 mpg) going up the hill. So I get "worse" mpg going down the hill...strange.

Seems to happen when giving slight throttle input + downward inclines.

So here's a quick summary:

Cruising, go down a slight hill, drive-train THUD, mpg goes to 14, get to bottom of slight hill, drive-train THUD, mpg goes to 22-26 or so, next incline, repeat.

Since my part of Michigan has very few flat roads, this can happen 50-60 times in a 2 hour trip...exhausting. Help!
 

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Could this be the VCM kicking on/off?
 

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Discussion Starter #3
Could this be the VCM kicking on/off?
Great question. After months of evaluation and riding with Tech's, it's not the VCM, IMO. On a flat surface, the van will go in/out of VCM with no noticeable transition.

With that said, the many complaints relative to VCM could actually be similar to "my issue" and not VCM related. Believe me, it's taken several thousand miles to come to that assumption. They are closely related, but different if you compare when it happens and what happens, namely getting 14 mpg going down a hill. Something seems to be loading the engine for the mpg indicator to do that. Also, I'm not claiming that the mpg indicator is anything magic, it's just giving an indication of vacuum pressure.

We intend to keep this van for 200,000, so I have a vested interest in a solution/fix.
 

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Bad/sticking thermostat? Which temperature sends a shift signal to the A/T?
 

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Discussion Starter #5
Bad/sticking thermostat? Which temperature sends a shift signal to the A/T?
Hmmm. No shift detected, and very little or no rpm change after each THUD.

The THUD seems to be a byproduct of something putting a load on the engine when it happens. That's also why the instant fuel economy drops like a stone too.

Thought that maybe the torque converter was locking/unlocking causing this, but the dealer said no. Problem was no better or worse after the torque converter was replaced for a different reason.

Grade logic was another thought, but that normally involves a downshift after you apply the brakes, I believe. I don't know.
 

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How old is your ATF? A 3X drain and refill (with Mobile 1, Red Line or other synthetic) is relatively easy to do, and is worth a try.
 

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Discussion Starter #7
How old is your ATF? A 3X drain and refill (with Mobile 1, Red Line or other synthetic) is relatively easy to do, and is worth a try.
Good call. That was the first thing they tried, but with the Honda spec fluid. If there was any change it was likely "placebo effect", so no difference. :frown:
 

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I have the exact same thing, but I always thought it was the Torque converter locking up,
as soon as the engine load was light enough.
It does not bother me as much.

However,
I do think that the thermostat, as a previous member posted, may actually be the culprit also.

I observed the following about the temp gauge:

When the temp gauge is hot, the needle is right at the bottom of the icon, (thermometer in water),
at about 1mm, almost touching the first line of the little icon.

If anyone here reports a dead center, in the middle, for the needle on their temp gauge,
I am changing my thermostat right the away.

If it really bothers you, try changing the thermostat.


Hello All:

I've been battling Honda on a very annoying transmission/drive-train "trait" that makes is almost impossible "for me" to drive the vehicle because it's very annoying once you are conscious of what's happening. If you notice you have the same problem after reading this...sorry!

2007 Touring. Had all software updates and torque converter replaced. Bought new, problem recognized at about 40,000 miles, now 78,000 miles, wifes van.

Here's what happens - Driving down the road at 65 mph, top gear, if I crest a small hill and head down the back side, still applying light throttle, I will get a THUD in the transmission/drive-train that can be felt by all passengers. Not a shift, nor does the rpm change. This happens EVERY time I have to ease up on the gas to keep a constant speed, but it seems to be most prevent when going down a slight grade/hill.

Not that this is related, but at the same time the thud happens, my instant fuel economy goes from 35+ mpg (remember, going down a slight grade) to 14-16 mpg, holds for a few seconds, then starts to ramp back up after yet another THUD. In some cases, I have gone down a large grade with slight throttle and the instant mpg holds at 14, then when I go up another subsequent incline the instant mpg will rise (20-22 mpg) going up the hill. So I get "worse" mpg going down the hill...strange.

Seems to happen when giving slight throttle input + downward inclines.

So here's a quick summary:

Cruising, go down a slight hill, drive-train THUD, mpg goes to 14, get to bottom of slight hill, drive-train THUD, mpg goes to 22-26 or so, next incline, repeat.

Since my part of Michigan has very few flat roads, this can happen 50-60 times in a 2 hour trip...exhausting. Help!
 

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I observed the following about the temp gauge:

When the temp gauge is hot, the needle is right at the bottom of the icon, (thermometer in water),
at about 1mm, almost touching the first line of the little icon.
Sounds like you are running to hot. The needle is damped but should be in the middle. I believe that as the car warms up the loop is open and the PCM checks the temp and the T/C will not lock up. When operating temp is reached the loop closes, bringing the O2 sensors into the loop and lockup is allowed. Too high a temp may also influence lockup. Maybe your stat is sticking. If you can get hold of a ScanGauge or similar to check, then the operating temp should be around 180 deg. F -- your specs may be different.
 

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...Sounds like you are running to hot. The needle is damped but should be in the middle... ...
Sinbad I think you mean too cold, not hot, or maybe you misread my post.
I said the needle is almost at the bottom of the icon- that is towards the cold side.

In other words, to get to the middle of the gauge temp, the coolant needs to
go another quarter inch or so hotter, or up, in this case.

Sooo, I maybe running too cold, and if so, you are still right about the cause being
a sticky thermostat, that does not close all the way, and is letting the coolant flow too soon,
or even constantly.
 

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When the temp gauge is hot, the needle is right at the bottom of the icon, (thermometer in water), at about 1mm, almost touching the first line of the little icon.
Not quite related to this OP's issue; however, I have the same needle position in my 2007 EX-L and often wonder if my thermostat is screwed - because I get 10mpg 90% city driving. I'm also contemplating scan-gauge or something of that nature, but haven't pulled the trigger on it or the thermostat yet. I also wonder if the temp needle settles exactly at mid-point or lower for others...
 

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Discussion Starter #13 (Edited)
Any codes? If so what are they?
No codes. That's a big contributing factor to the frustration because no codes means "nothings wrong"...right...:mad:

I have the exact same thing, but I always thought it was the Torque converter locking up,
as soon as the engine load was light enough.
It does not bother me as much.

However,
I do think that the thermostat, as a previous member posted, may actually be the culprit also.

I observed the following about the temp gauge:

When the temp gauge is hot, the needle is right at the bottom of the icon, (thermometer in water),
at about 1mm, almost touching the first line of the little icon.

If anyone here reports a dead center, in the middle, for the needle on their temp gauge,
I am changing my thermostat right the away.

If it really bothers you, try changing the thermostat.
I'll have to take a look-see this weekend... Seems like a bit of a longshot, but it's part of the process of eliminating variables.
 

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Hello All:

I've been battling Honda on a very annoying transmission/drive-train "trait" that makes is almost impossible "for me" to drive the vehicle because it's very annoying once you are conscious of what's happening. If you notice you have the same problem after reading this...sorry!

2007 Touring. Had all software updates and torque converter replaced. Bought new, problem recognized at about 40,000 miles, now 78,000 miles, wifes van.

Here's what happens - Driving down the road at 65 mph, top gear, if I crest a small hill and head down the back side, still applying light throttle, I will get a THUD in the transmission/drive-train that can be felt by all passengers. Not a shift, nor does the rpm change. This happens EVERY time I have to ease up on the gas to keep a constant speed, but it seems to be most prevent when going down a slight grade/hill.

Not that this is related, but at the same time the thud happens, my instant fuel economy goes from 35+ mpg (remember, going down a slight grade) to 14-16 mpg, holds for a few seconds, then starts to ramp back up after yet another THUD. In some cases, I have gone down a large grade with slight throttle and the instant mpg holds at 14, then when I go up another subsequent incline the instant mpg will rise (20-22 mpg) going up the hill. So I get "worse" mpg going down the hill...strange.

Seems to happen when giving slight throttle input + downward inclines.

So here's a quick summary:

Cruising, go down a slight hill, drive-train THUD, mpg goes to 14, get to bottom of slight hill, drive-train THUD, mpg goes to 22-26 or so, next incline, repeat.

Since my part of Michigan has very few flat roads, this can happen 50-60 times in a 2 hour trip...exhausting. Help!
Grade Logic System monitors throttle position, vehicle speed,
acceleration and deceleration. Based on this information, the system
can determine if the vehicle is on an incline and adjusts the shift
schedule for improved climbing power or downhill engine braking. It
provide downshifts from fifth to fourth or from fourth to third as
required on downhill grades, making effective use of engine braking
to control the vehicle's speed.
 

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Discussion Starter #15
Grade Logic System monitors throttle position, vehicle speed,
acceleration and deceleration. Based on this information, the system
can determine if the vehicle is on an incline and adjusts the shift
schedule for improved climbing power or downhill engine braking. It
provide downshifts from fifth to fourth or from fourth to third as
required on downhill grades, making effective use of engine braking
to control the vehicle's speed.
Thanks for the explanation. I saw something similar after I decided to do a little more research on GL. What I've described definitely doesn't fall under the category of grade logic since no shifting is involved, nor any rpm change. The THUD happens because something is "applying" a load to the engine. THUD happens again when the load is "released". Odd.

I'll take it one step further - Every grade change has 2 THUD's, once as I head down the back side of a small grade change and once again a random period there after (light throttle at all times to maintain speed). Now, if I wait for the first THUD and watch the instant MPG meter I'll see the fuel economy peaking at about 35+ mpg and it will drop like a stone (after the THUD) to 14-16 mpg, BUT, if I blip the throttle while it's dropping it will interrupt the cycle and the instant MPG will rebound to high 20's, low 30's as you would expect on a downward grade...and the second THUD "doesn't" happen (or might happen during the throttle blip, but all I feel is the throttle blip I did).
 

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Discussion Starter #17
Faulty motor mount(s)?
Had them check those as part of the initial evaluation, but they checked out. Also, if they were bad, it would be hard to correlate that to the behavior of the instant MPG meter and how closely it matches to the THUD's.


>>Wondering if anyone else can confirm that their instant MPG tends to drop down and hold at 14 or so MPG for a short period of time for no apparent reason. Is this normal?<<
 

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...Not quite related to this OP's issue...
Yes it is related, if the torque converter keeps locking on and off because engine is not allowed to be fully warmed up from a sticky thermostat.
 

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Sinbad I think you mean too cold, not hot, or maybe you misread my post.
I said the needle is almost at the bottom of the icon- that is towards the cold side.

In other words, to get to the middle of the gauge temp, the coolant needs to
go another quarter inch or so hotter, or up, in this case.

Sooo, I maybe running too cold, and if so, you are still right about the cause being
a sticky thermostat, that does not close all the way, and is letting the coolant flow too soon,
or even constantly.
You are correct. My thermometer icon is at the top, hottest end of the scale. This is more conformation you are too cold. You gotta get hot to get the T/C to lock up. Thermostat should be on the driver's side of the engine where the lower radiator hose connects.
 

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I got the same problem and this is where the needle is at all the time.
 
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