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Discussion Starter · #1 ·
I have a 2003 i4 with an automatic. When I drive down a flat stretch of road at around 37-38 MPH with the RPMs around 1750 the RPMs begin to oscillate. The engine speed drops to 1700 then back to 1750, drop to 1700 then back to 1750, etc. This occurs in roughly one second intervals. You can feel and hear this oscillation when it happens and you can watch the RPM needle moving back and forth. Has anyone else heard of this problem? Let me know if there are any other details I can give.
 

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Elvira
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I have a 2003 i4 with an automatic. When I drive down a flat stretch of road at around 37-38 MPH with the RPMs around 1750 the RPMs begin to oscillate. The engine speed drops to 1700 then back to 1750, drop to 1700 then back to 1750, etc. This occurs in roughly one second intervals. You can feel and hear this oscillation when it happens and you can watch the RPM needle moving back and forth. Has anyone else heard of this problem? Let me know if there are any other details I can give.
How does it idle? Do rpm's fluctuate while at idle?

How is the coolant level in the radiator? Overflow tank?

Do you have heat in the car?

Can you get the rpm to stop oscillating if you press down a little further?

Is there a dead spot in the acceleration?

Miker
 

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Discussion Starter · #3 ·
Hey Miker, I appreciate the questions...

How does it idle? Do rpm's fluctuate while at idle?
Idles just fine. No fluctuation.


How is the coolant level in the radiator? Overflow tank?
Coolant is in the middle of the min and max in the resovoir.


Do you have heat in the car?
The heat seems good.


Can you get the rpm to stop oscillating if you press down a little further?
Yes.


Is there a dead spot in the acceleration?
Not that I can tell.
 

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Elvira
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Hey Miker, I appreciate the questions...

How does it idle? Do rpm's fluctuate while at idle?
Idles just fine. No fluctuation.


How is the coolant level in the radiator? Overflow tank?
Coolant is in the middle of the min and max in the resovoir.


Do you have heat in the car?
The heat seems good.


Can you get the rpm to stop oscillating if you press down a little further?
Yes.


Is there a dead spot in the acceleration?
Not that I can tell.
So, if it happens consistantly at the rpm's you stated, everytime that is, it may be the throttle position sensor. Do you drive at this rpm/speed a lot? Sometimes keeping TPS in same position over life of a car can wear it out in that position. Slightly moving it up or down outside the bad spot allows it to "fix" the fluctuations.

I asked about coolant since low coolant or air in system can affect the ECT sensor (Engine Coolant Temperature) sensor and sometimes the air pocket will make ECT reading erratic. The temp changes and tells ECU to increase or decrease RPM's cause it thinks coolant isn't warmed up yet. So will low coolant.

Miker
 

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Discussion Starter · #5 ·
Just a hunch, but it seems that it happens when the car has just enough inertia at that RPM range on flat ground for the computer to justify using 5th gear, but maybe since it's right on that threshold of 4th and 5th it can't decide if it should hold 5th or prepare to drop to 4th.
 

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Discussion Starter · #7 ·
I can feel it. It's like [throttle for half a second] then [no throttle for half a second] repeat. Like a pulsating behavior.
 

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Discussion Starter · #8 ·
It's not a huge deal really since if I maintain a speed of either (35 or less) or (38 or higher) the problem doesn't occur. But it still has me stumped and I'd love to get to the bottom of it, especially if it might be indicative of bigger problems later on.
 

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I've felt that too on my 2003 automatic. normally when hovering 1800-2000 rpm feels like pulsations and u can see it on the rpms. Doesn't happen always though.
 

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I <3 My Honda
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Any way you could take us a video of it?
 

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Transmission fluid needs changing in part. I have a 2007 Accord VP I4 AT, 14,000 miles, (Mom's car). Similar problem 4th gear up and down 200 RPM each second at 35 Mph level road steady cruise, 5th gear same at 45 MPH. This is around 1500 to 1800 rpm. The Fluid was at the lower mark on the dipstick.

The 2003 - 2007 Service Manual I purchased and Parts Manager, said low fluid and high time on fluid causes some of these problems (Shellac/goo in the valve body). Fluid must be checked within about 1 minute after driving it, not on a cold engine.

Changed fluid with Honda H type cured the 200 rpm rise and fall every second. However I had a 30 to 50 to 75 RPM occasional fluctuation as observed on a digital Scangage which lessened as miles piled up after the first fluid change.

I delayed the second 3 quart change for a few hundred miles to have the fresh fluid clean the varnish on the valve body so that the drain took more of the goo out of the system,--- and the transmission performed even better each day driven and Tachometer spin up into second and maybe third lessened till barely noticed.

After second 3 quart change after each few hundred miles shifts became more positive and no Tachometer spin up noticed. After driving the car for a while the RPM Hunting completely stopped at 50 MPH and higher. However, slight fluctuations are still noticed around 1400 to 1600 rpm in 4th and 5th at 35 and 45 MPH but hopefully are getting less and less.

The I4 has a transmission filter in the cooler return line just below the fuse box under the hood. That needs to be changed after I drive it a few more miles. NAPA sells a replacement larger 3/8 inch inlet/outlet Power Steering filter with a heavy magnet ring in it for $9.45. It works and is 1/2 to 1/3 the prices I found on line.

NAPA P/S Filter (Add-On Type 3/8th I&O also works for transmissions) Part Number: PS 351002 Power steering fluid and ATF are the same in some cars and the filter works with all as I have read. http://www.clublexus.com/forums/ls4...-magnetic-trans-or-power-steering-filter.html

The direction of fluid flow is toward the rear of the car. This filter and most other filters are directional because they have a relief valve if the filter is clogged.

I am waiting till I have a few more hundred miles and then change the filter to see if it stops the transmission hunting and helps the shifting. If it is partially clogged it is restricting the cooling fluid going back to the pan and possibly restricting the fluid pressure in the transmission allowing the RPM to fluctuate or hunt until the RPM of the engine boost the pressure to lock the converter positively at 50 or so. Another post said this filter change caused a definite quicker, lower rpm positive shifting. The OEM is under 20 at Honda, Maybe,-- if you are lucky but is half the size, is made of metal and has no magnet to trap micro fine particles. This Napa Magnafine filter is slightly larger and needs a zip tie to affix it to the filter mount.

Let me know what you have found out so far.
 

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I have a 2003 i4 with an automatic. When I drive down a flat stretch of road at around 37-38 MPH with the RPMs around 1750 the RPMs begin to oscillate. The engine speed drops to 1700 then back to 1750, drop to 1700 then back to 1750, etc. This occurs in roughly one second intervals. You can feel and hear this oscillation when it happens and you can watch the RPM needle moving back and forth. Has anyone else heard of this problem? Let me know if there are any other details I can give.
Is your AC on? Did you recently charge it? if so, maybe it's overcharged? If not, maybe it's low on freon so the AC clutch kicks in every few secs?
 

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Discussion Starter · #13 ·
Last month I did an ATF drain and fill. I've never done this myself and the last time I paid the shop to do it was at least 4-5 years ago. I expected to drain out 3 quarts but only got 1 quart. However, when I filled it took 3 quarts. Apparently I was in fact low on ATF fluid. I haven't noticed the RPM issue since ensuring the proper ATF level. Thanks for the feedback, guys. I'll update if the RPM thing comes back again. Hopefully this post can be of value to anyone else dealing with this problem.




Transmission fluid needs changing in part. I have a 2007 Accord VP I4 AT, 14,000 miles, (Mom's car). Similar problem 4th gear up and down 200 RPM each second at 35 Mph level road steady cruise, 5th gear same at 45 MPH. This is around 1500 to 1800 rpm. The Fluid was at the lower mark on the dipstick.

The 2003 - 2007 Service Manual I purchased and Parts Manager, said low fluid and high time on fluid causes some of these problems (Shellac/goo in the valve body). Fluid must be checked within about 1 minute after driving it, not on a cold engine.

Changed fluid with Honda H type cured the 200 rpm rise and fall every second. However I had a 30 to 50 to 75 RPM occasional fluctuation as observed on a digital Scangage which lessened as miles piled up after the first fluid change.

I delayed the second 3 quart change for a few hundred miles to have the fresh fluid clean the varnish on the valve body so that the drain took more of the goo out of the system,--- and the transmission performed even better each day driven and Tachometer spin up into second and maybe third lessened till barely noticed.

After second 3 quart change after each few hundred miles shifts became more positive and no Tachometer spin up noticed. After driving the car for a while the RPM Hunting completely stopped at 50 MPH and higher. However, slight fluctuations are still noticed around 1400 to 1600 rpm in 4th and 5th at 35 and 45 MPH but hopefully are getting less and less.

The I4 has a transmission filter in the cooler return line just below the fuse box under the hood. That needs to be changed after I drive it a few more miles. NAPA sells a replacement larger 3/8 inch inlet/outlet Power Steering filter with a heavy magnet ring in it for $9.45. It works and is 1/2 to 1/3 the prices I found on line.

NAPA P/S Filter (Add-On Type 3/8th I&O also works for transmissions) Part Number: PS 351002 Power steering fluid and ATF are the same in some cars and the filter works with all as I have read. http://www.clublexus.com/forums/ls4...-magnetic-trans-or-power-steering-filter.html

The direction of fluid flow is toward the rear of the car. This filter and most other filters are directional because they have a relief valve if the filter is clogged.

I am waiting till I have a few more hundred miles and then change the filter to see if it stops the transmission hunting and helps the shifting. If it is partially clogged it is restricting the cooling fluid going back to the pan and possibly restricting the fluid pressure in the transmission allowing the RPM to fluctuate or hunt until the RPM of the engine boost the pressure to lock the converter positively at 50 or so. Another post said this filter change caused a definite quicker, lower rpm positive shifting. The OEM is under 20 at Honda, Maybe,-- if you are lucky but is half the size, is made of metal and has no magnet to trap micro fine particles. This Napa Magnafine filter is slightly larger and needs a zip tie to affix it to the filter mount.

Let me know what you have found out so far.
 

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Mike
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With a V6 AT, one thing to watch out for if fuel/air/vacuum has been eliminated : When driving in D (sometimes even D3) on a relatively steady throttle at 30 to 40 MPH and you notice a 50 to 100 RPM change every few seconds, this may be the Torque Convertor lockup clutch hunting. Something that should be avoided. - Can occur at higher speeds but usually with a higher RPM change (100 to 200 RPM). Obviously the TC is going to lock/unlock when load changes but it's that repetitive cycling you want to avoid.

Quite often a High FM fluid like Z1 and DW-1 will mask this. More noticeable with aged/oxidised oil. Sometimes a drain/fill hides it, but it's still there - just happens slowly and so is not as noticeable, but it still wears/heats the TC clutch.


Edit - A dirty filter will cause restricted flow through the TC, bad for the TC - Oil bypasses the filter cooler line and is fed directly to the sump so in reality the trans is not starved of oil but it will overheat. The cooler - filter is not a full flow circuit, only some of the oil goes through the filter cooler at any given time, the rest bleeds/flows back to the pan/sump. Over a relatively short time all of the ATF is filtered and cooled.
 
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