srt44116

quick question for you guys. Would a bad tps sensor cause a auto transmission to only shift when the rpms are high or do you think its more than that. Its a pending sale of a friend and there clam is its a bad tps sensor, thats why it shifts messed up?????


thanks alot guys oh ya its a 94 xj

VTJeep

high rpm issues are more commonly associated with the IAC valve. idk if your 94 has one... i think it does.. either way, i wouldnt take their word for it. get it on a good code reader and see what it says. are there any other physical symptoms you know of? sporadic idle, hesitations, popping/backfiring at manifold? that said, do you know if all fluid levels are good and that the fluid themselves are good?

srt44116

Its a 1990 xj auto. i will see what codes it has. i just wonder if its a tranny issue or of the trannys talks to the tps. if the tps was bad it woulnd not know when to shift????

VTJeep

wait.. what?...

ZINGGG

Haha *confusion*

Is it a 94 or a 90?

If it's a 94, you got an idle air control valve that attaches to the throttle body. That's more than likely associated with rpm problems. Tps has more to do with your idle. However a tps is about 30 or 35 bucks and really easy to replace. And can be bought under warranty just about anywhere. So if you think that's the problem, buy it and replace it. And if it doesn't fix it then you'll be able to take it back

89Renix

The TPS, could cause that, the renix are super finicky...

now if it is a 90 it should have the sport comfort setting between the steerting wheel and the rear wiper controls. try both selections. the "sport setting" is higher rpms and a more harsh shift.

comfort is smooth low shift points, the more "comfortable" setting

tjwalker

Yes, need to clarify the year. First post you say 94, then you say 90.

Throttle position is absolutely suspect here, regardless of the year.

It's signals are critical to shift points. Below is more about the TPS for the 91-01. The TPS for the 87-90 is way different. If you need information on that, you'll need to clarify the year.
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The throttle position sensor is connected to the throttle shaft on the throttle body. It sends throttle valve angle information to the PCM. The PCM uses this information to determine how much fuel the engine needs. The TPS is really just a simple potentiometer with one end connected to 5 volts from the PCM and the other to ground. A third wire is connected to the PCM. As you move the accelerator pedal with your foot, the output of the TPS changes. At a closed throttle position, the output of the TPS is low, about a half a volt. As the throttle valve opens, the output increases so that, at wide open throttle, the output voltage should be above 3.9 volts. Testing can be performed with an electrical meter. Analog meter is best. You are looking for a smooth sweep of voltage throughout the entire throttle band. While slowly opening and closing the throttle, take note to the movement of the voltmeter needle. There should be a direct relationship between the needle motion to the motion of the throttle. If at anytime the needle moves abruptly or inconsistently with the movement of the throttle, the TPS is bad

You should have 5 volts going into the TPS. At idle, TPS output voltage must be greater than 200 millivolts. At wide open throttle (WOT), TPS output voltage must be less than 4.8 volts.. The best is to use an analog meter (not digital) to see if the transition from idle to WOT is smooth with no dead spots. With your meter set for volts, put the black probe on a good ground like your negative battery terminal. With the key on, engine not running, test with the red probe of your meter (install a paper clip into the back of the plug of the TPS) to see which wire has the 5 volts. One of the other wires should show .26V (or so). The other wire will be the ground and should show no voltage. Move the throttle and look for smooth meter response up to the 4.49 at WOT.

Perform the test procedure again and wiggle and/or tap on the TPS while you watch the meter. If you notice any flat spots or abrupt changes in the meter readings, replace the TPS.

The TPS is sensitive to heat, moisture and vibration leading to the failure of some units. The sensor is a sealed unit and cannot be repaired only replaced. A TPS may fail gradually leading to a number of symptoms which can include one or more of the following: -

NOTE: The throttle position sensor is also DIRECTLY involved with transmission shifting characteristics! It should be verified early in the troubleshooting process, when a transmission issue is suspected!

• Poor idle control: The TPS is used by the ECU to determine if the throttle is closed and the car should be using the Idle Air Control Valve exclusively for idle control. A fault TPS sensor can confuse the ECU causing the idle to be erratic or "hunting".
• High Idle Speed: The TPS may report faulty values causing the engine idle speed to be increased above normal. This is normally found in conjunction with a slow engine return to idle speed symptom.
• Slow engine return to idle: A failing TPS can report the minimum throttle position values incorrectly which can stop the engine entering idle mode when the throttle is closed. Normally when the throttle is closed the engine fuel injectors will be deactivated until a defined engine RPM speed is reached and the engine brought smoothly to idle speed. When failing a TPS will not report the throttle closed and fueling will continue causing the engine to return to idle very slowly.
• Engine Hesitation on Throttle Application: The TPS is also used by the ECU to determine if the driver has applied the throttle quicker than the Manifold Air Pressure sensor can read. The fueling is adjusted acordingly to cope with the sudden increase in air volume, however a faulty sensor can cause the ECU to ignore this data and the engine will "hesitate" when applying the throttle. In extreme cases with the engine at idle, a sudden application of full throttle can stall the engine.
• Engine Misfire: A fault TPS can report values outside the deined acceptable range causing the ECU to incorrectly fuel the engine. This is noticable as a slight misfire and can trigger the misfire detection software and/or Malfunction Indicator Lamp (MIL) light on the dashboard. Extreme cases can cause excessing misfires resulting in one or more cylinders being shut down to prevent engine and catalytic converter damage.

freegdr

detent cable adjusted correctly?

cruiser54

Haven't we established it is a shifting RPM issue and not a high idle issue?

Original post indicates it's shifting late. Nothing about idle.

TPS is definitely suspect.

If it's a 1990, there are no codes to pull and the ECU and TCU do not communicate to each other. I don't think 94 does either for that matter.