Torque Converter on auto seems to unlock

[Taz]

Been doing some searching on the TDR and have found a few discussions about Auto transmission problems but none that exactly fit my particular circumstances.



This only happens at interstate speeds, so far. Cruising along the interstate I can set the cruise at say around 75 mph, and the TC will unlock on hills and anytime the engine gets under a load. However if I punch the pedal to the floor it will lock up again. Also if I do not set the cruise and just foot it at that speed this problem doesn't seem to occur.



Since I can make it lock back when I press the throttle to the floor I would think the TPS is working correctly... no?



Thankx

 

[Extreme1]

No!

Sounds like your TPS and my TPS have been chatting. I'm chatting with mine right now! :-{} #@$%!



Check the voltage at the center pin (stick a paper clip up through the wire end with it connected). With the key (engine off) on you should get 1. 2 volts at idle and 3. 5 at WOT.



My guess it is really low and needs to be adjusted. Or else bad.

 

[Taz]

hrm now I must find this infamous TPS!



So many things to work on, ARGH!!!



Be so glad when I get me another truck, 97 extended cab, with a MANUAL!

 

[Strick-9]

Check TPS voltage with an analog voltage meter and not a digital one.



Check the voltage at idle and WOT, but also apply the throttle slowly and watch for a smooth transition with no 'bad spots. '



A few times when sensors are used in the same location for long periods of time it may go bad at that location but no where else.



So you may have a spot on the throttle that has a huge lack of voltage and the PCM thinks you are letting off on the throttle and unlocks the converter. At other throttle positions it would work fine.



If that is the case, sometimes you can loosen the bolts to the TPS and rotate it slightly so your cruise control won't hold the throttle in the 'bad' spot.



Hope that helps. Good luck,

Chris

 

[Blakers]

Also if I do not set the cruise and just foot it at that speed this problem doesn't seem to occur.

You say it only does it with the cruise on?



Check the adjustment of the brake light/cruise control switch on the brake pedal to be sure it isn't too sensitive to your brake pedal bouncing around. When I first got my truck, everytime I hit a little bump in the road the cruise quit. I bent the bracket holding the switch slightly and all has been fine now.



Blake

 

[Taz]

Originally posted by Blakers





You say it only does it with the cruise on?



Check the adjustment of the brake light/cruise control switch on the brake pedal to be sure it isn't too sensitive to your brake pedal bouncing around. When I first got my truck, everytime I hit a little bump in the road the cruise quit. I bent the bracket holding the switch slightly and all has been fine now.



Blake

I have experienced this problem too on really rough interstates. But the other problem I'm talking about, the cruise stays ingaged just unlocks the TC.



Thankx for the tip, I will adjust that too.

 

[Extreme1]

The actual repair is even easier!

Originally posted by Blakers

Check the adjustment of the brake light/cruise control switch on the brake pedal to be sure it isn't too sensitive to your brake pedal bouncing around... I bent the bracket holding the switch slightly and all has been fine now.

Blake

Push the pedal down and pull the plunger for the switch out, it ratchets!

 

[shendren]

from my library and from experience... . (check your transmission temp sensor, engine speed sensor, brake switch)



you need some paperclips. 7mm socket on 1/4" drive...



TPS Adjustment

The throttle position sensor, shift lever, and throttle valve cable are critical to proper operation of the transmission. If one or more of these are out of adjustment or if the TPS is noisy, shifting will be erratic. Before performing any adjustments, check the transmission fluid level and sniff the fluid. Do not make any adjustments until the fluid level is correct, and burned fluid has been replaced.

The service manual says to adjust for 0. 8-1. 2V at idle. On many trucks, this voltage is too low, resulting in TCC chatter at moderate throttle loads. The TPS is not officially adjustable but the mounting holes are slotted and the body can be rotated slightly. Adjustment is relatively easy, and requires only a digital voltmeter and a few hand tools. A little adjustment goes a long way...

TPS wire color code:

• Black = ground

• Orange/dark blue stripe (center pin) = signal

• Purple/white stripe = 5V power

Testing and adjusting the TPS:

1. With the key "OFF", unplug the connector from the TPS.

2. Turn the key "on" and insert DVM probes into the connector to reach the connector pins. Short pieces of wire or paper clips can be used to extend the DVM probes for reaching into the connectors.

3. Read from the purple wire to the black wire (these should be the outside pins). Power should be 5V with the key "on".

4. Turn the key "off" and plug the connector back onto the TPS

5. Insert the leads from the digital volt meter into the back of the TPS connector. The DVM negative probe goes into the back of the connector cavity with the black wire. The positive DVM probe goes into the back of the connector cavity with the orange signal wire.

NOTE: Push the probes into the rear of the connector until the probe tips reach the metal connector pins.

6. Loosen the TPS mounting screws

7. With the engine off and key on: Adjust the TPS position for 1. 2 to 1. 5V on the signal wire with the throttle at the idle position - more voltage makes more TC clutch pressure, too much will set a fault code. Often, adjusting for 1. 4 to 1. 5V at idle will cure TC clutch chatter under light load conditions. NOTE: The factory setting is 1. 2V max, so proceed carefully.

8. Tighten the TPS screws, slowly open the throttle to the WOT position and then return return to idle. Watch for voltage jumps - the voltage should change smoothly from the idle value to at least 3. 5V at WOT (5 volts is all you should be able to get). If the sensor voltage jumps or drops unexpectedly - replace the sensor or try the filter modification below.

Posted to a TPS thread on the TDRoundtable by Bill Kondolay (Bill is one the true transmission experts out there):

Note: I did some minor editing to put it into the context of this web page - Dave.

Before anyone follows advice on how to adjust the TPS keep in mind that every action has a reaction. You can adjust the TPS voltage to pretty much what ever you want without following Chryslers procedures. Before starting, always record your original idle voltage; you must have a baseline to start from.

Make adjustments in small increments. First remove the TPS, knock out the 2 steel sleeves, with a small file oblong the holes, and install the tps sensor. Always start with the original voltage you had; as you increase your voltage your OD and TCC lock up will start to come in later and later. The down side of doing this is that when you slow down or if you remove your foot from the throttle, the TCC will not unlock unless you step on the brake pedal or your vehicle speed drops below a certain setting.