1998 Dodge Ram 1500 from North America - Comments

Hey, was searching around for some RPM info and came across this which may help you. http://dodgeram.org/tech/transmission/automatic/TPS_adjust.htm.

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.

TPS Filter Construction - Bring a dead TPS back to life.

Steve Clayton Gemcuttr1@cs.com sent this simple technique for filtering the output of a noisy TPS.

I did some experimenting and found that an electrolytic capacitor (440 microFarads, 35 Vdc) with the negative side connected to the SIG RETURN wire and the positive side hooked to the TPS SIG wire gave me absolutely *troublefree* operation! Even though my TPS is basically trashed, the capacitor filters out almost all of the electrical noise, and my auto tranny once again shifts like factory-new!

I dug into the wire bundle coming out of the PCM and soldered the capacitor as close to the plug as I could manage - thinking some "TPS problems" may actually be wiring/connector problems in disguise.

Results with other values were:

* 220 mF, 35 Vdc - too little filtering. Tranny a little flaky.

* 1000 mF, 35 Vdc - far too much filtering, and a 1.5 second delay in transmission shift response crept in.

BTW, I might add that since I added the capacitor, my cruise control hasn't dropped out even once in 15K miles - usually a twice-per-week occurence (I drive 1500 miles a week). What I believe is that the dropout problem is caused by an electrical noise spike from the TPS - which is *exactly* what the capacitor filters out.

Please consider this tip a free gift for oilburner fans! The capacitor costs just 40 cents, and I hope it will save TDR members and others lots of money! After all, you can by a lot of #2 diesel for $200! :-)

I own a 98 Dodge 5.2 liter truck. When driving and the air conditioner is on and blowing using the vent, when I push on the gas as little as 300 rpm, the air will stop coming out of the dash vents and will be directed to come out of defroster for windshield. As I let off the gas, it goes back to blowing air from the dash vent. It just started that after being in the shop at the Dodge place. I had just had a intake manifold gasket replaced, any ideas about what's going on?

There is a vacuum line check valve in the engine compartment on the right side of the intake manifold, try replacing that. It fixed the vent problem in my 2001 1500. Now I'll try some of the suggestions on the engine surging, the PCM re-flash and torque converter lockup and TPS sound like they fit the symptoms.

The vacuum supply to the Heater A/C System may drop when accelerating or when speed control engages. This may cause the vacuum motor to switch to the defrost position. Along with this it was common for the cruise to fail also. First check for any vacuum leaks, if none are found then it is usually due to leaking vacuum hose at speed control servo, due to battery acid leaking or seeping down on the servo hose or servo diaphram. You have to remove the battery tray to get to it.

The other cause was a bad or missing check valve. Locate the vacuum source line to the heater A/C system in the engine compartment. Install the vacuum check valve in the Heater A/C system vacuum line. Make sure that the check valve is installed to allow vacuum to pass into the Heater A/C system, but block any vacuum drop when accelerating. The original check valve is at the manifold end of the vacuum lines. It has a larger hose than the ones going to the reservoir. I don't know what size or how much the one they specify is, but I know a NAPA 2-1015 has about the right size ends to match the lines going to the Heater A/C system line. It costs $4.98 and PEP Boys has a #03308612552 for $4.79 that is the same one.

NOTE: DO NOT INSTALL THE VACUUM CHECK VALVE IN THE VACUUM LINE GOING TO THE RESERVOIR OR THE SPEED CONTROL SERVO. INSTALLING THE VACUUM CHECK VALVE IN THE LINE GOING TO THE VACUUM RESERVOIR OR THE SPEED CONTROL SERVO WILL HAVE A NEGATIVE EFFECT ON THE SYMPTOM / CONDITION AND POSSIBLY CAUSE THE SPEED CONTROL SYSTEM TO DROP VACUUM WHILE ACCELERATING.

My 2001 Ram 1500 also had the surge problem, which got worse as the engine warmed up. It wasn't a problem below 45, but when I got on the highway it felt like it was slipping in and out of overdrive, especially when I went over a bump. I just replaced the throttle position sensor and it seemed to have stopped the problem. The weather is cool currently. I don't know how it will work in the heat of the summer, which seemed to have made the problem worse.