Acceleration problems: this thread is only for the gifted

[3p141592654]

There are two problems here, and I will go on record as saying they are unrelated.

The surging you speak of, my car does that. Has done it since new, when it was under warranty long long ago, and still does it today. When I lived in NJ it would always do it coasting into the toll booths on the garden state parkway. Toyota had no fix, and I didn't want them to pull the tranny which in the end was the only stone left unturned. It seemed worse when the A/C was on, and to me it felt like the lockup was going in and out repeatedly. My guess is that it is a ECT computer issue, and therefore unfixable. For whatever reason, I rarely notice it these days though.

Now for the throttle binding, as stated above remove the line pressure cable and see if it helps. Does the binding occur with the engine off sitting in your driveway?

One thing that comes to mind is the pivot contraption on the top of the valve covers. That has a nylon bushing that can fail. Maybe you can let us know if you have replaced it. Unfortunately, I believe it is now discontinued from Toyota.

 

[Scot]

Perhaps get it on a Dyno so you can actually see and feel the problem from under the hood.....

 

[johnathan1]

The fact that you feel it press against your foot before the weirdness occurs, suggests to me that it could be the cruise control...try unhooking the cruise control cable from the throttle body and see if that helps at all.

 

[jdub]

^^^

It's a "line pressure up" cable...the A340 tranny does not have a kick down cable

It will drive fine with out it connected...harsher shift perhaps, but you will not damage the tranny. Disconnect the cable (note where the stop nuts are positioned) and take it for a spin. You might want to try the same thing with the cruise control cable.

 

[IJ.]

Shifts will be softer and slippier with it disconnected

 

[dezthumper]

It's a "line pressure up" cable...the A340 tranny does not have a kick down cable It will drive fine with out it connected...harsher shift perhaps, but you will not damage the tranny. Disconnect the cable (note where the stop nuts are positioned) and take it for a spin. You might want to try the same thing with the cruise control cable.

I will disconnect the line pressure up cable tonight or this weekend and see what happens.

The fact that you feel it press against your foot before the weirdness occurs, suggests to me that it could be the cruise control...try unhooking the cruise control cable from the throttle body and see if that helps at all.

I will disconnect this after doing the line pressure up cable so I don't feel it "work perfectly" and then scratch my ars wondering which route gave forth the solution to this phenom.

There are two problems here, and I will go on record as saying they are unrelated.

The surging you speak of, my car does that. Has done it since new, when it was under warranty long long ago, and still does it today. When I lived in NJ it would always do it coasting into the toll booths on the garden state parkway. Toyota had no fix, and I didn't want them to pull the tranny which in the end was the only stone left unturned. It seemed worse when the A/C was on, and to me it felt like the lockup was going in and out repeatedly. My guess is that it is a ECT computer issue, and therefore unfixable. For whatever reason, I rarely notice it these days though.

Replacing the TPS certainly reduced the lurching effect but it still does it - however, if others have experienced it, I will cross the off the "could be related list." My other Supras didn't do this, however, 4 of 5 of them were stick shift and therefore there was a direct connection between the engine and the tranny without the clutch disengaged.

Does the binding occur with the engine off sitting in your driveway?

It pedal pressure phenomonon ONLY take place while in drive. If in Neutral, Park, EngineOn or EngineOff - it is perfect and free flowing and the original OEM floor mats, though it want to move toward the front of the car and bunch up, is kept away from the throttle every time I get in the car and during stops I just find myself pulling it back. I actually have a means of keeping that back - a piece out of a new Tundra might do the trick of keeping the carpet from scooting around. The little rubber teeth on the back don't do their job very well any more...

One thing that comes to mind is the pivot contraption on the top of the valve covers. That has a nylon bushing that can fail. Maybe you can let us know if you have replaced it. Unfortunately, I believe it is now discontinued from Toyota.

I will take a look at the pivot point there on the passenger side valve cover - we did this before, but why not look one more time? Everything there is tight adn all measurements checked and rechecked with a micrometer...

 

[dezthumper]

Ok guys, got home, disconnect the cruise once again. No change, came home, disconnected the "kick down liner pressure cable" and it runs normal.

The tranny, without the line pressure cable connected feels as if the converter or something isn't locking up as good. Just seems like the car is a little less crisp or ... as if the engine isn't as directly connected to the engine.

So now that it is almost certain to lie somewhere in the tranny, is it of your opinion that it lies in the valve body?

The cruise control throttle cable, the pedal throttle cable and the line pressure cable are all new.

The mechanism controller all of these cables is tight with zero flopiness or looseness.

When I pull the line pressure cable - it actually feels a little pressure when I pull it to the 3/4 point - it is a very easy cable to pull yet there is a little resistance in the cable from the 3/4 point to full out. But NOTHING like the pressure needed when it is in drive - I have to place about 80-100 lbs of pressure on it to "bust" through the "snag" or "pressure" ... I took the car out for a 5 mile city loop then took her on the highway for a high-speed run. It just seems a little off - not as crisp.

Since there appears to be so much engineering with a cable and mechanism and all that for this line pressure cable, what does it do? What EXACTLY is its meaning in life - the more details the better.

 

[turbojuiced]

IMHO from reading all these posts to me it sounds like a ecu problem or the actual tranny itself.

You pretty much excacerbated every possible thing or option you and techs and gurus can think of. The only 2 left are the actual main big ones.

Just my .02

I mean you went over all the usual things it could be for that type of problem. The vale body, solenoid valve, linkage, throttle cable, all linkage, and the list goes on. The only thing left is the actual tranny and ecu itself.

 

[jdub]

You could start by reading the TSRM
http://www.cygnusx1.net/supra/Library/TSRM/MK3/manual.aspx?S=AT&P=3

It's called a "throttle cable" or referred to as "throttle pressure"...what it really does is increase hydraulic line pressure as a function of physical throttle position through the hydraulic control unit. This is why your shifts don't feel as "crisp" with it disconnected.

More on this:
http://www.cygnusx1.net/supra/Library/TSRM/MK3/manual.aspx?S=AT&P=6

You might want to check for tranny codes:
http://www.cygnusx1.net/supra/Library/TSRM/MK3/manual.aspx?S=AT&P=14

If the cable is binding on the bell crank inside, you will have to drop the pan.
Start here:
http://www.cygnusx1.net/supra/Library/TSRM/MK3/manual.aspx?S=AT&P=51

Be very careful about keeping the bolts and parts in order...they need to go back in exactly the same place.

BTW - this is not the ECU or the ETC...it's mechanical.

 

[turbojuiced]

You could start by reading the TSRM
http://www.cygnusx1.net/supra/Library/TSRM/MK3/manual.aspx?S=AT&P=3

It's called a "throttle cable" or referred to as "throttle pressure"...what it really does is increase hydraulic line pressure as a function of physical throttle position through the hydraulic control unit. This is why your shifts don't feel as "crisp" with it disconnected.

More on this:
http://www.cygnusx1.net/supra/Library/TSRM/MK3/manual.aspx?S=AT&P=6

You might want to check for tranny codes:
http://www.cygnusx1.net/supra/Library/TSRM/MK3/manual.aspx?S=AT&P=14

If the cable is binding on the bell crank inside, you will have to drop the pan.
Start here:
http://www.cygnusx1.net/supra/Library/TSRM/MK3/manual.aspx?S=AT&P=51

Be very careful about keeping the bolts and parts in order...they need to go back in exactly the same place.

BTW - this is not the ECU or the ETC...it's mechanical.

He said there were no codes and he said he also did a complete fluid and filter change along with a brand new torque converter.

The tsrm is definitely a great place to start but from what the op said he has already done this and pretty much already have put a new tps and throttle cable on. Im very interested to find out what it is as well as it seems a couple people have similar problems. Good thing I dont have an auto :naughty:

 

[jdub]

He said there were no codes and he said he also did a complete fluid and filter change along with a brand new torque converter.

The tsrm is definitely a great place to start but from what the op said he has already done this and pretty much already have put a new tps and throttle cable on. Im very interested to find out what it is as well as it seems a couple people have similar problems. Good thing I dont have an auto :naughty:

Reading comphrension
A fluid change will not do squat if the line pressure up bell crank or cable inside is binding.

He didn't mention a new TC...did say he did a complete fill though.
Question here...have you dropped the pan?

I did miss him checking codes.

 

[turbojuiced]

Reading comphrension
A fluid change will not do squat if the line pressure up bell crank or cable inside is binding.

He didn't mention a new TC...did say he did a complete fill though.
Question here...have you dropped the pan?

I did miss him checking codes.

ugh! reading comp pwnes! :biglaugh: And yes the tc was in the op and same with the fill. At least thats what I gathered but its kinda late for me so I could be missing somehting lol.

 

[turbojuiced]

"What have I done to this point to find a solution?
* ensured the carpet is not in the way of the throttle pedal assembly
* checked the linkage
* replaced the linkage
* rechecked the linkage
* removed plenum
* inspected "butterfly valve" and complete throttle assembly
* checked freeplay
* removed and replaced cruise control
* replaced exhaust for fear of some weird back-pressure gremlin (part of the cat had come apart and was floating around in there)
* replaced TPS
* R*R tranny fluid and filter with complete torque converter drain and fill
* inspected tranny fluid carefully and had it paper filtered looking for anything that might be wrong inside the tranny."

OP

 

[jdub]

Pretty sure he didn't pull the tranny to drain/fill the TC
All you have to do is disconnect the tranny line to the cooler and run the car while you pour ATF in the dipstick tube (after you drain the pan and fill of course)...complete replacement of fluid. In fact, I'm doing this tomorrow myself.

The TSRM has a pretty good description of how this works...including line pressure. His question on line pressure prompted my comments and links to the appropriate pages.

 

[turbojuiced]

"Pretty sure he didn't pull the tranny to drain/fill the TC
All you have to do is disconnect the tranny line to the cooler and run the car while you pour ATF in the dipstick tube (after you drain the pan of course)...complete replacement of fluid. In fact, I'm doing this tomorrow myself.

The TSRM has a pretty good description of how this works...including line pressure. His question on line pressure prompted my comments and links to the appropriate pages. "

"Well, having had three certified Toyota techs, two tranny shops, two automotive ASE techs, myself spending untold hours researching this problem on the forums and finally downloading the classroom texts used to teach tranny techs and Toyota techs about the Aisen A340E, or 30-40LE, transmission - I think it just might be the mechanism that the kickdown/line pressure cable operates. Oh yeah, I also replaced the kick down cable. "

 

[jdub]

"Well, having had three certified Toyota techs, two tranny shops, two automotive ASE techs, myself spending untold hours researching this problem on the forums and finally downloading the classroom texts used to teach tranny techs and Toyota techs about the Aisen A340E, or 30-40LE, transmission - I think it just might be the mechanism that the kickdown/line pressure cable operates. Oh yeah, I also replaced the kick down cable. "

That's exactly why I'm confused...you have to lift the valve body to disconnect the cable. All these smart people didn't actuate the mechanism to see if it was binding? And, the OP is still confused on what line pressure does?

Tell you what Juiced, you have a good handle on rehashing what's been done. I'll just leave it to you to offer anymore advice..I got better things to do anyway.

 

[turbojuiced]

That's exactly why I'm confused...you have to lift the valve body to disconnect the cable. All these smart people didn't actuate the mechanism to see if it was binding? And, the OP is still confused on what line pressure does?

Tell you what Juiced, you have a good handle on rehashing what's been done. I'll just leave it to you to offer anymore advice..I got better things to do anyway.

No! I really want to know what this is too. Thats why I am helping you understand what the OP has done already. So that you can properly diagnose. But ok maybe the techs did not do this already. Hopefully he will come back and let us know what he finds inregards to that.

 

[dezthumper]

No! I really want to know what this is too. Thats why I am helping you understand what the OP has done already. So that you can properly diagnose. But ok maybe the techs did not do this already. Hopefully he will come back and let us know what he finds inregards to that.

Lots of good comments and suggestions and even I am having a hard remembering all the things I've read so far and done to the car to diagnose.

I hope this captures and clarifies what I've done with respect to some of the questions above.

The pan was removed.
I did use a magnet to find and remove any possible metal or brass shavings - Was told metal indicates bearing - gear - clutch plate wear and brass (non magnetic) indicates bushing wear. There were very very fine little pieces in the oil but nothing showing concern. I keep that fluid like new with complete fluid changes every 15k - it is always fresh and has never been burnt.

The TC was not removed. We did do a complete drain and fill though - whereby he hooked it up to some cool machine and let the engine run and it gets everything in the TC as well as the tranny itself. We also changed the tranny filter/screen just to be safe since we were already in there.

The valve body removal... I am unsure about - the throttle cable (line pressure cable) was replaced with a brand new OEM unit but my mechanic did this without me there. If the valve body must be removed to replace this piece, then yes, the valve body was removed.

The "throttle cable/line pressure cable" felt free and zero binding and was adjusted to spec - there are two lock nuts that hold that in place and the tension and adjusments there are right on.

Removing this line pressure cable last night got rid of the throttle pressure "push back phenomenon" but the car certainly doesn't have as much "connection" between the engine and the tranny, almost as if the cluthes or something aren't fully engaged. After rereading the TRMS someone kindly gave me the links to above, it appears that the line pressure cable helps or communicates to the ECT to increase/decrease line pressure. Without proper pressure, the tranny is not fully locking the TC????

I am not a mechanic but certainly like to learn - however, the TRMS page located here: http://www.cygnusx1.net/supra/Library/TSRM/MK3/manual.aspx?S=AT&P=6

Has my limited exposure to this cool stuff over powering my eyeballs - I get light headed (not really) trying to read it since I am not really sure what it is saying.

Maybe if I ask a question like this:
In layman terms, what is that page saying - what exactly is happening now that I disconnected the line pressure cable? What exactly, again, in terms this 40 yr old brain can handle w/ltd mechanical exposure, does the line pressure cable do - physically - to the tranny.

Granted, tracing the problem to that mechanism the line pressure cable controls is a Godsend. However, the car seems to have lost a few ponies - I assume being lost in the newly introduced inefficiencies caused by incorrect line pressure.... ????

I am very lucky that there is someone that has a working complete valve body on this forum and he has offered to ship it to me, including shipping, for $50. I am waiting on tranzparts.com to pull their craniums out of their rears and get me a complete valve body - they sent me an incomplete one and it has been like pulling teeth to get it right. KILLING ME!

Anyway, forgive my rambling but I hope to have covered those questions from above.

I sure wouldn't mind learning what exactly this cable does...

 

[jdub]

In laymen's terms
Line pressure is the "force" that effects shifts, engages the clutch packs, and engages TC lock-up. Inadequate line pressure = soft (or no) shift, slipping clutch packs, and it would not surprise me if the TC did not lock up. This fits what you are experiencing with the cable disconnected. I told you to disconnect the cable as a diagnostic for the "resistance" you felt through the accelerator pedal...you definitely do not want to leave it disconnected.

Here is where this is pointing to:
http://www.cygnusx1.net/supra/Library/TSRM/MK3/manual.aspx?S=AT&P=111

This page shows the top view and the bell crank/throttle valve interface:
http://www.cygnusx1.net/supra/Library/TSRM/MK3/manual.aspx?S=AT&P=112

Marked circled "A" on the diagram...the throttle valve could be sticking, the spring binding, or the throttle valve cam (bell crank) and the down shift plug (roller) interface is binding. If you have a known good valve body on the way, that should fix the problem.

 

[dezthumper]

In laymen's terms
Line pressure is the "force" that effects shifts, engages the clutch packs, and engages TC lock-up. Inadequate line pressure = soft (or no) shift, slipping clutch packs, and it would not surprise me if the TC did not lock up. This fits what you are experiencing with the cable disconnected. We told you to disconnect the cable as a diagnostic for the "resistance" you felt through the accelerator pedal...you definitely do not want to leave it disconnected.

Here is where this is pointing to:
http://www.cygnusx1.net/supra/Library/TSRM/MK3/manual.aspx?S=AT&P=111

Marked circled "A" on the diagram...the throttle valve could be sticking, the spring binding, or the throttle valve cam (bell crank) and the down shift plug interface is binding. If you have a known good valve body on the way, that should fix the problem.

PERFECT! That diagram was the best exploded view I've seen of it. It is exactly A, in that schematic, that tranzparts.com did NOT include in the valve body they sent me. I thought it was more of a plunger, but it appears to be a "plug" that rotates by control of the line pressure cable/throttle cable. This stuff is pretty cool - never knew how an automatic tranny really worked and STILL don't but am getting the idea. I can't imagine how the new Lexus 8 speed auto must work - all the electronics in that must equate to a mini super computer???