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Hey guys,

My girlfriends 2001 DX (automatic-193,000 miles) has randomly not been shifting into overdrive lately. On the highway at about 70, the engine is at about 3000 RPM+. I have mechanical experience, but aren't too familiar with honda's. Do you have any suggestions? It seems to randomly shift normally, and then some days, won't shift at all into overdrive no matter how fast you go. It doesn't seem like its a TPS problem....

To clear something up (dumb question, but have to ask), these cars have 5-speed automatics, correct? For some reason I keep seeing 4-speed automatics online, but am 99% sure I have counted the car shift through 5....

Where should I start?

Thanks for the help,

Sean

EDIT: After further searching, it sounds 3000 RPM is normal at about 70 MPH. Why does it seem like the engine is screaming all of a sudden? Even my girlfriend noticed it, and said its been sucking gas like its its job. The motor sounds normal, just seems to be revving so high on the highway sometimes compared to others...

 
Rep Power: 517

It's a 4 speed, with a lockup torque converter.
3k@70MPH doesn't SOUND unusual, but I don't drive one of those cars every day. I might pay attention to how many "shifts" I see/hear/feel while driving.

If you think it isn't in 4th gear@70, pull the stick back to D3 at 70MPH and see what happens.

Tires aired up? Brakes not dragging? Car lot loaded down with junk?

Things scream when they are in PAIN. Don't you do that too? LOL

Did the muffler fall off? Noisy tires? Wheel bearing bad? Tach or speedo inaccurate?

Don't compare to anything but an identical car.
That would be 01-05 DX or LX for you, IIRC.
Engine RPM at any given indicated road speed is strictly a function of gear ratios. You can't alter it without a lot of money.


Document it. Write down gallons and miles in a log book every time you fill the gas tank. Calculate gas mileage at every fill up.
If I got a work order that said the same thing you did up there, there wouldn't be much concern because there is no documentation.
Only a vague "feeling", but zero proof.
And the cost of the gas has nothing to do with mileage.

Does it run bad? CEL on?

 
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Thank you very much for the response Ezone. I think you just figured out all of my confusion haha. I'm not too familiar with automatics (always have worked on manuals), and I didn't realize these cars had a lockup torque converter. The RPMs dropping when the converter locks im pretty sure is what I was mistaking for going into "5th gear". (stupid me). So it seems like the converter is not locking....

I'm planning to change the trans fluid because to my knowledge, it has not been changed in a long time. Any suggestions on fluid, proper way to change it, etc?

I will calculate gas mileage ASAP. Wheel bearing/tire noise has been dealt with, the tires are at perfect pressure, the brakes are fine, and there are no CELs. I don't think the speedo/tach is inaccurate. I'm 99% sure that the converter is the problem...Shouldn't I be getting a CEL for the converter not locking?

Where should I start? My searching has pulled up alot about code P0740 and replacing the torque converter clutch solenoid and A/T clutch pressure control solenoid valve. Chances these are causing the problem without throwing the code?

 
Rep Power: 517

If it wasn't locking, you wouldn't have thought it had that 5th gear.

I can usually watch the tach and see when the TC goes into lockup at highway speeds. If it unlocks at a steady speed, the RPM change can be minimal like only 100-200 RPM so it is quite subtle.

Drain and fill ONLY.
Hondas ATF DW-1 is my choice (I'm a dealer tech).

Others here like Valvoline Maxlife, or Dexron 6.

If you want to flush it, that is only several drain and fill sessions. DO a search here, I have posted a link to the methods several times.
Flush machines and chemicals are "strongly discouraged" in official documents.
One drain and fill is a about 2.5-2.75 US quarts.

Probably would have a P0740 for lockup system malfunction.
Slim.


On a scanner, even a cheap one that has some sort of datalist capability: Drive the car on the highway and see what the coolant temperature says (after warmup, obviously). It had better be at 180 or above. Anything under that can kill gas mileage.

 
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I really appreciate the help Ezone.

I have driven the car when it was functioning normally. When I "counted" the gears, I felt/saw the RPMs drop (like it was shifting into 5th)...I guess thats why I thought it had a 5 speed auto. There is a distinct difference in the car when it doesn't "lock up". It seems like its winding out 4th gear.

I'm going to change the fluid Saturday (multiple times to flush it out a bit).

I have a scanner and will check the coolant temperature. What parameters does the torque converter read to lock up? I'm sure road speed, Throttle position, temp. all play a factor. Just trying to figure out what might be throwing it off to not lockup if in fact the torque converter is still healthy.

Thanks again.

 
Rep Power: 517

Ah.
I'm thinking it can hold off 4th and lockup if the temp is low enough, to speed up warmup in cold temperatures.
Not sure what temps that actually happens at though.


But low operating temperature can kill a lot of gas mileage by itself.

It's not completely electronic, there's hydraulic controls involved. The TCC solenoid enables operation, hydraulic pressures (CPC sol.) actually control and modulate the application of the TCC.

If a good scanner, I'd be watching TCC enable, and engine RPM and mainshaft speed. Engine and mainshaft should be the same speed when the TCC is locked.......but you really have no way of knowing what the hydraulic controls are doing inside the trans. You would need some good trans shop manuals and trans pressure gauges for troubleshooting that system if you really wanted to get into it..

I'll go a different route:

To set a TCC P0740 code (quote from service info): The mainshaft speed is 89% -99% or less than the engine speed (depending on vehicle speed and throttle position) for at least 16 seconds.
You don't have any TCC codes.
This tells me that whatever the trans is doing must be acceptable to the computer, otherwise it would code for TCC malfunction.


I can't tell what is REALLY happening with your car, so I'll toss out a scenario:

So if the car has something else going on (such as a large load, brake dragging, or running poorly) that is causing you to apply extra throttle to keep your speed up, then the trans very well could be doing what it thinks it should-- for the conditions it sees.

When the TCC is engaged, you should be able to tell that it only takes a little extra throttle to make it disengage (watching the tach, rpm raises a couple hundred), then reapply again after the road speed and throttle are steady again.
A strong headwind might make lockup turn off.
Make any sense?

 
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According to the temp. gauge in the car it is up to temp, but i'm going to double check with my scanner. I only have a somewhat basic scanner with a small amount of live data, so I don't think i'll be able to see what the TCC is doing.

Your "scenario" makes complete sense, BUT i'm still very confused over the whole thing. I have literally sat in the car and TRIED to make it shift (or lockup). Seeming like it may have been throttle position or road speed related, I did everything from varying the throttle position, to coasting at 80+, etc.

I'm confused why i'm not getting a code. I know i'm probably sounding a little crazy but there is a distinct difference in the car on the highway from day to day.

So here's my game plan so far (will happen tomorrow):

1) Flush ATF over the course of a few days
2) Verify proper operating temperature
3) Verify that the TPS is reading correctly (checking TPS% on the highway with scanner)

I wish this thing would just throw a code already so we would have some more direction....

 
Rep Power: 517

Gauge is not much better than a glorified idiot light. The normal place the needle stays covers a broad range of temps.
Trust a datalist for accurate readings, not the gauge.

Because the computer doesn't consider it a problem.