HELP Cruise Control is unlocking Torque Converter???

[e304runner]

Hi, I recently purchased a 2003 4Runner SR5 V8 4x4 and love it; except when I'm on the highway. I noticed the mileage wasn't quite what I thought it should be even for a v8. Just by chance I set my cruise at 70mph exactly and noticed that the rpms were at 2000 exactly also. This was fine, but some time later I looked up to find the rpms at 2250. I was puzzled. I started playing with the cruise control system (on a 5 hr drive from Fresno, CA to Redding, CA) and have deduced the following. All conclusions were based on driving from 60 -85 mph.

-When the cruise control is set to a given speed it will unlock the torque converter at some point. It appears to be random, any where from 1-20 minutes or so later.

-I cannot reproduce the unlocking phenomenon with my foot on the throttle. It must be under the control of the cruise control to unlock.

-When the torque converter is locked and cruise is on (and everything is functioning as it should) I can accelerate the car with the cruise control or the pedal and it will remain locked in 5th/ Over Drive and accelerate, quite hard before kicking down a gear or even unlocking; as it should.

-Sometimes the converter will unlock slowly, as in, hold at 2050 for a few seconds then move to 2100 for a few seconds, then to 2150 and so on until it reaches approximately 250rpms over where it should be if locked. Sometimes it will unlock completely within a second.

I can take over from the cruise control with my foot, while cruise is still engaged, but not accelerating much, and then cancel the cruise control, the rpms will instantly drop indicating the converter has locked, and i can push resume and the converter will stay locked for some indeterminate amount of time as indicated above.

-The torque converter WILL NOT relock while the cruise control is holding the vehicle speed, it must be canceled, but not completely turned off.

-It would appear the mechanical functioning of the torque converter and lock up is ok, but idk.

- Once I was aware of the issue I was able to watch for it and reset the cruise when it would unlock, this improved my mpg by 1.5-2 mpg!!!

Please Please, any and all help would be appreciated. Im at a loss, and am fairly mechanically inclined.

Pleas help me get my :llama: running strong again. :help:

 

[rtuck1]

Hi, I recently purchased a 2003 4Runner SR5 V8 4x4 and love it; except when I'm on the highway. I noticed the mileage wasn't quite what I thought it should be even for a v8. Just by chance I set my cruise at 70mph exactly and noticed that the rpms were at 2000 exactly also. This was fine, but some time later I looked up to find the rpms at 2250. I was puzzled. I started playing with the cruise control system (on a 5 hr drive from Fresno, CA to Redding, CA) and have deduced the following. All conclusions were based on driving from 60 -85 mph.

-When the cruise control is set to a given speed it will unlock the torque converter at some point. It appears to be random, any where from 1-20 minutes or so later.

-I cannot reproduce the unlocking phenomenon with my foot on the throttle. It must be under the control of the cruise control to unlock.

-When the torque converter is locked and cruise is on (and everything is functioning as it should) I can accelerate the car with the cruise control or the pedal and it will remain locked in 5th/ Over Drive and accelerate, quite hard before kicking down a gear or even unlocking; as it should.

-Sometimes the converter will unlock slowly, as in, hold at 2050 for a few seconds then move to 2100 for a few seconds, then to 2150 and so on until it reaches approximately 250rpms over where it should be if locked. Sometimes it will unlock completely within a second.

I can take over from the cruise control with my foot, while cruise is still engaged, but not accelerating much, and then cancel the cruise control, the rpms will instantly drop indicating the converter has locked, and i can push resume and the converter will stay locked for some indeterminate amount of time as indicated above.

-The torque converter WILL NOT relock while the cruise control is holding the vehicle speed, it must be canceled, but not completely turned off.

-It would appear the mechanical functioning of the torque converter and lock up is ok, but idk.

- Once I was aware of the issue I was able to watch for it and reset the cruise when it would unlock, this improved my mpg by 1.5-2 mpg!!!

Please Please, any and all help would be appreciated. Im at a loss, and am fairly mechanically inclined.

Pleas help me get my :llama: running strong again. :help:

I have had the same problem in the past. It happens every now and again still. I have no idea what it is or why it happens. I have taken it to the dealer and they say they can not get it to reproduce the problem.

Robert

 

[Kmvreter]

Hi, I recently purchased a 2003 4Runner SR5 V8 4x4 and love it; except when I'm on the highway. I noticed the mileage wasn't quite what I thought it should be even for a v8. Just by chance I set my cruise at 70mph exactly and noticed that the rpms were at 2000 exactly also. This was fine, but some time later I looked up to find the rpms at 2250. I was puzzled. I started playing with the cruise control system (on a 5 hr drive from Fresno, CA to Redding, CA) and have deduced the following. All conclusions were based on driving from 60 -85 mph...

-The torque converter WILL NOT relock while the cruise control is holding the vehicle speed, it must be canceled, but not completely turned off.

...

Thanks for the thorough description. Sounds like you have a good handle on the issue.
Is this happening on level ground or are there inclines involved?
Mine is a V6 but that shouldn't matter as the same principles are involved. I do a fair bit of highway driving and played with this at various speeds on the same stretch of road with a long incline (slighty steady grade.) I notice that the rpm's increase slightly (converter lockup cycles off) if I am at a slower set speed/lower initial rpm, then it drops back in rpm as it locks back up, then repeats this on/off cycle 3 times on this stretch of road. The tranny isn't downshifting unless I am initially set at a much lower speed. I noticed that at an initial higher set speed/higher rpm the lockup doesn't normally cycle. It might only cycle once due to a head wind on particular days. All this is what I call normal.
In all cases the converter will lock back up and the rpm will drop without any driver input by me. I don't have a solution but can you try to replicate it on an incline. See if the cruise does or doesn't allow the lockup at the level top coming out of a grade?

 

[wareagle98]

2003 v8 sport for me, does the same thing. First noticed it on the first long trip I took. I have a fairly long commute each day, and I notice this on my commute as well.

Conditions under which my 4r will do this are: when on cruise, descending a hill steep enough to back way out of the throttle. This will unlock the converter, and it usually will not lock back up on its own on CC. OR when climbing a hill steep enough on cruise to cause the converter to unlock, but not steep enough to cause a downshift to fourth. Usually will not re engage is this case, either.

If tranny does downshift completely to fourth while the cruise control is on, it will lock the converter on the upshift.

When not using the cruise, converter will unlock and re lock normally via input from the gas pedal.

When mine does this on cruise, I either move the stick to 4 to make a complete downshift, then back to drive, or disengage and reset the cruise via a tap on the brake and resume.

I agree, have to keep an eye on the rpms to catch this happening. I theorize that the throttle by wire may be the culprit, in conjunction with the cruise. Again, mine locks up normally when CC is not engaged. I just keep an eye on the tach. Luckily the v8 is strong enough that most hills dont unlock the converter. I find mine unlocking more on a downhill....

 

[e304runner]

Rtuck1 and wareagle98 sounds like we are having the same problems. Wish we could figure this out. I played with this problem on a flat road I-5 north/south and found it occurring at what seemed like random intervals. Would be interesting to see if it occurs on the downhill more.

Kmvreter, coverter will not lock up until cruise has been canceled. It is possible it would lock up if I made transmission shift to 4th by tapping the shifter over. I will try this weekend as I will be doing some more highway driving.

Thanks for the help and consideration guys, keep it coming. Lets figure this out.

 

[rtuck1]

2003 v8 sport for me, does the same thing. First noticed it on the first long trip I took. I have a fairly long commute each day, and I notice this on my commute as well.

Conditions under which my 4r will do this are: when on cruise, descending a hill steep enough to back way out of the throttle. This will unlock the converter, and it usually will not lock back up on its own on CC. OR when climbing a hill steep enough on cruise to cause the converter to unlock, but not steep enough to cause a downshift to fourth. Usually will not re engage is this case, either.

If tranny does downshift completely to fourth while the cruise control is on, it will lock the converter on the upshift.

When not using the cruise, converter will unlock and re lock normally via input from the gas pedal.

When mine does this on cruise, I either move the stick to 4 to make a complete downshift, then back to drive, or disengage and reset the cruise via a tap on the brake and resume.

I agree, have to keep an eye on the rpms to catch this happening. I theorize that the throttle by wire may be the culprit, in conjunction with the cruise. Again, mine locks up normally when CC is not engaged. I just keep an eye on the tach. Luckily the v8 is strong enough that most hills dont unlock the converter. I find mine unlocking more on a downhill....

I had trouble with mine in the hills, once it would unlock down the hill it would not re-lock going back up and jump from OD into sometimes 3rd when it would be completely uncalled for. I would take CC off and it would climb the hill in OD no problem. Like i said, it is not EVERY time, but enough that i do not use CC very often.

My friends mother has a Lexus LS 430 and hers did the same. She took it to the dealership and they replaced the torque converter and the problem went away.

I personally am not concerned about the torque converter going out but can say it definitely does not cooperate with CC.

 

[JB.]

Hi, I recently purchased a 2003 4Runner SR5 V8 4x4 and love it; except when I'm on the highway. I noticed the mileage wasn't quite what I thought it should be even for a v8.....

......-The torque converter WILL NOT relock while the cruise control is holding the vehicle speed, it must be canceled, but not completely turned off.

The cruise control is not very sophisticated and most of what you described sounds pretty normal to me except for the above point if it's consistently true on level ground without too much head wind. If it truly won't lock up again at all once it's unlocked, that point would concern me. What happens if you tap it down 1 mph in that circumstance? I'm thinking that may be enough of a nudge to allow it to lock. If I'm pushing gusty head winds at 80mph while using cruise control, it's not unusual for me to put it in 4th gear and just leave it there where the TC will pretty much stay locked and will definitely re-lock if it ever does unlock. In the same conditions without cruise control, the truck will hold 5th gear TC locked much, much more easily.

FWIW, there's a 7% grade near here that is 5 miles long. With cruise ON, the truck downshifts to 3rd and stays there at 65mph for the length of the grade. With cruise OFF and a steady pedal, the truck will downshift to 3rd and build a little speed above 65mph allowing a shift to 4th where the speed will slowly come down, then the process will repeat a few times for the length of the grade but allow quite a bit of time to be spent in 4th gear, TC locked.

On long, rolling highway drives without much traffic around, I often play a game where I tap the cruise to accelerate 2-4mph (2-4 times) approaching a hill and then try to keep the TC from unlocking up the hill with the same number of well timed deceleration taps. It's an amusing way to pass time and used this way the cruise control can actually be an aid to mpg instead of a drag on it.

Anyway, it sounds like you don't mind experimenting so I'd be interested to hear what happens with single taps.

 

[stevec5000]

I recently drove across Texas and back and never noticed anything like that, it just droned on at the same RPM the whole way and back. However, how do you tell if the Torque Converter is locked or unlocked? There's no light or anything to tell you is there?

 

[JB.]

However, how do you tell if the Torque Converter is locked or unlocked? There's no light or anything to tell you is there?

You take note of the rpms at a certain speed in 4th or 5th gear during easy cruising and compare against that. From that point, with the right amount of throttle, you can induce a small rise in the rpms without inducing a downshift. That's the TC unlocking.

 

[e304runner]

The cruise control is not very sophisticated and most of what you described sounds pretty normal to me except for the above point if it's consistently true on level ground without too much head wind. If it truly won't lock up again at all once it's unlocked, that point would concern me.

I have definitely tried to increase and decrease speeds with the cruise control in an attempt to get the converter to re-lock, but with no success.

A couple times I set the cruise at 75mph, on a completely flat road (I-5 N.), with no or very little head wind. I waited for the unlock to occur (it does it randomly IMO) then decreased speed using the cruise control to 65mph; the converter would not re-lock ever. It just continued to hum along at 65 mph in 5th, unlocked.

Each time I had to take over with my foot on the throttle and cancel cruise control. [I must stress this point. When I took over control with the throttle pedal, I would as slowly as possible ease into the gas pedal, as to increase my speed ever so slightly (1-2mph or so). Once I could feel that I had depressed the gas pedal to a point where i was providing the throttle input and not the cruise control I would hold this speed with my foot and I would immediately cancel the cruise control at which point the converter would immediately re-lock.] Then the cruise control can immediately be re-engaged and it will then hold the new speed, in 5th, converter locked, for some indeterminate amount of time. Usually less than 15 min.

IMO it seems like a computer glitch. Possibly the cruise control computer or tps sensor because they are the only systems that may cause this problem and are involved in cruise operation. I'm aware that the brake-light sensor is also involved, but in its malfunction cruise will usually not engage.

One member has suggested pushing the shifter into 4th and then releasing back to fifth while allowing cruise control to maintain control and to see if that will allow the converter to re-lock once back in 5th. I will try that this weekend as I have about 2 hours of highway driving to do.

 

[e304runner]

BTW, not to be rude, but none of what I am trying to describe is normal operation. I have a decent grasp on how torque converters operate and this is far from normal.

At no time when this problem occurs, is load being increased on the drive-train, therefore there should not be any unlock of the converter. It would be ludicrous to think that Toyota designed a system that unlocks without a load increase on the drive-train. It would kill gas mileage on a car that already struggles to obtain a decent mileage.

 

[Kmvreter]

I have definitely tried to increase and decrease speeds with the cruise control in an attempt to get the converter to re-lock, but with no success...

IMO it seems like a computer glitch...

I'm thinking it's a mechanical issue.

The computers/ECMs are constantly doing a circuit self test. They are very good at setting a code and warning light at the first sign of an internal computer or circuit issue. No light means no computer/sensor issue.

I'll point back to what was mentioned above in the Lexus example. What if the torque converter is mechanically malfunctioning and causing more "drag" in the driveline? Then it may be unlocking as a response to what it senses: a physical need for more torque. I'm thinking this could happen at a random time as internal "drag" in the converter increases and causes the unlock. If the "drag" in the system continues then the converter won't see anything different and stays unlocked. In this case the computer is doing the job correctly.

Not sure if I explained correctly what I'm thinking but hope this helps.

Also, you mention buying the truck used. Do you know the service history? Has the A/T ever been worked on? I know it's supposedly "life-time" fluid but I would start with a fluid change. Cheap maintenance "insurance". Maybe it's something as simple as a low fluid level.

 

[Evan B]

Is it the A/C compressor kicking on and off?

 

[JB.]

A few drains and fills is where I would go (after a level check, of course). They have been known to fix some odd TC behavior.

http://www.toyota-4runner.org/4th-g...trip-transmission-issue.html?highlight=rumble

 

[e304runner]

I'm thinking it's a mechanical issue.

The computers/ECMs are constantly doing a circuit self test. They are very good at setting a code and warning light at the first sign of an internal computer or circuit issue. No light means no computer/sensor issue.

I'll point back to what was mentioned above in the Lexus example. What if the torque converter is mechanically malfunctioning and causing more "drag" in the driveline? Then it may be unlocking as a response to what it senses: a physical need for more torque. I'm thinking this could happen at a random time as internal "drag" in the converter increases and causes the unlock. If the "drag" in the system continues then the converter won't see anything different and stays unlocked. In this case the computer is doing the job correctly.

Not sure if I explained correctly what I'm thinking but hope this helps.

Also, you mention buying the truck used. Do you know the service history? Has the A/T ever been worked on? I know it's supposedly "life-time" fluid but I would start with a fluid change. Cheap maintenance "insurance". Maybe it's something as simple as a low fluid level.

HI, thanks for the detailed response. With regard to the computer I see your point and appreciate the insight, and thought. I would have to agree with your analysis of the computer systems.

I have 2 questions or issues with your theory of drag increasing in the drive-line/ t-converter.

#1 is that I absolutely cannot reproduce the "symptoms" or the "problem" while driving with my foot. Only when in cruise will the vehicle perform as described. I have maintained as even/steady a throttle position with my foot as humanly possible for extended periods and never seen the issue.

#2, when the issue does come up, I have tested it by slowly slowly slowly applying pressure to the gas pedal, just until a point where I know I am giving the the throttle input to the vehicle and the cruise has been over ridden but is still activated (as if you were going to pass someone with cruise activated). The T-converter still remains in its unlocked position. I then hold this pressure on the pedal and cancel the cruise, the RPM's immediately fall as the converter re-locks. I can then push resume on the cruise control and the cruise will re-engage and the converter will remained locked for some amount of time. Keep in mind, during this operation the speed of the vehicle/grade/wind/ etc. did NOT change at all. This suggests to me, that it just wont re-lock with the cruise engaged (thats where I came up with it being a computer issue.)

I have not maintenanced the trans. fluid yet. I bought it used, one owner out of Hollywood, CA. Service records indicate most of its services were done at Toyota of Hollywood. Center diff appears to have been opened at one point, as there is quite abit of orange sealant on the outside of the case where the parts meet (not factory job). Ive been told by a friend that these center diffs often leak, and most likely it was opened to reseal, and stop leak.

 

[e304runner]

Is it the A/C compressor kicking on and off?

All tests performed with climate control and AC off. So no.

 

[e304runner]

A few drains and fills is where I would go (after a level check, of course). They have been known to fix some odd TC behavior.

http://www.toyota-4runner.org/4th-g...trip-transmission-issue.html?highlight=rumble

Since have yet to figure out what is causing the issue, I was going to do this next. A true flush (filling and draining multiple times) takes a lot of fluid so I am reluctant to try. And, the fluid in the vehicle is at the correct level when warm, and is fresh ( fairly new). So, I am reluctant to try this without further diagnosis that would point towards the fluid.

Only thing i could think with the fluid, b/c I didn't' put it in, maybe its not the correct rating or type.

 

[wareagle98]

I chimed in back on page one with the exact same symptoms. Absolutely, this occurs only with the cruise control on, not when driving with my foot. I believe this is just how it is with these vehicles. After some thought, I believe a few things are working together to create this.

I think that the electronic control of the transmission plays a large part in this, particularly the fact that the transmission is supposed to learn your driving habits and adjust accordingly. This implies monitoring and manipulation of shifts. I also believe that the sensor that downshifts on a descent also contributes; I say this because my v8 runner always delays shifting when I accelerate from a stop and immediately the road goes downhill. This ALWAYS happens to me when I take off from one particular traffic light. Speed limit is 45 there, and gentle acceleration up to this speed always results in my tranny holding 4th gear FAR longer than is necessary. Similar conditions also produce similar results.

Thus I think that this is normal behavior from this electronically controlled auto tranny when cruise is engaged. I just try to keep a close eye on the tach when cruising

 

[luvmyt4r]

Hey there. It sounds like the same problem I was having with my 2004. Come to find out it is "normal". It has to do with the programming in the computer. Here is the link to what I posted about a year ago.

http://www.toyota-4runner.org/4th-gen-t4rs/111600-annoying-cruise-issue.html

I hope it helps.

 

[wareagle98]

Hey there. It sounds like the same problem I was having with my 2004. Come to find out it is "normal". It has to do with the programming in the computer. Here is the link to what I posted about a year ago.

http://www.toyota-4runner.org/4th-gen-t4rs/111600-annoying-cruise-issue.html

I hope it helps.

Yah, this is it exactly. I figured it had to be "normal", since it consistently did the same things under the same conditions. Thanks for the info and the validation