my 93, 4.0L cherokee was occasionally stalling. In testing the old TPS, I was getting 5 volts, but the middle lead at WOT I was only getting 3.9 maximum. It did go up smoothly in voltage though. I pulled the code 24 and replaced TPS. Jeep ran fine that day, then next day it won't start. The engine cranks and cranks but doesn't even try to turn over. I hear the fuel pump noise too. I checked this morning, and I'm not getting any codes now, just the 55. Is it possible that I have a defective TPS? Would that cause a no start now that the engine is cold?

 

is it in correctly? it has to go in in the proper alignment or no go

 

Where did you buy your TPS?

It is NOT unusual to get a DOA engine management sensor right out of the box.

It is common with ebay sensors. Please don't buy sensors on ebay unless brand name is confirmed! Crap sensors are also not unusual with aftermarket, but reliability is very good with MOPAR sensors. Because of that, I will only install OEM sensors.

Test your new sensor. Or for a quick and dirty test, reinstall your old one and see if the engine starts. Gotta look at "cause and effect" and recent work performed. And that is the TPS.
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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 accordingly 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 denied acceptable range causing the ECU to incorrectly fuel the engine. This is noticeable 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.

 

I bought the BWD sensor at Oreilly's

the new TPS tested o.k.
I unplugged and re-plugged the CPS and now it starts. Cleaned up the terminals a bit. However, I did get a strange shift from 2nd to 3rd on a short test drive.
could that strange shift be related to the CPS going out?

 

A crank sensor would have nothing to do with shift points.

That new TPS however, could be related. The throttle position sensor is directly involved with shifting characteristics of the AW4 transmission.

 

Make sure in replacing the TPS you didn't injure or dislodge any wires or vacuum lines going to other things like the MAP sensor etc.

 

GOT SPARK?

 

i checked and everything looks hooked up, and connectors connected. I also pulled the IAC and gave it a good cleaning. It idles better than before and runs better too. Just the strange shift. The other thing I did was the adjustment of the kick down cable, but I did that a while back before cleaning IAC and code for TPS.
any more thoughts?
also, does cleaning the CPS connection buy me more time, or should I replace it?

 

never mind missed this...

 

UPDATE

drove fine yesturday on a few short trips. But this morning it died twice on the freeway going 55-60. Could that be a symptom of the CPS? I'm not getting any trouble codes

 

Very possibly the crankshaft position sensor. It often fails thermally (when engine is hot) and only gives codes about 25% of the time.

Another suspect for thermal failure is your ignition coil, but the crank sensor fails more often.

If you end up buying a crank sensor, please do yourself a favor and buy a Mopar unit from Jeep. Aftermarket crank sensors are "hit and miss" with a lot of miss. And a genuine crank sensor is about the same money.

 

thanks, but actually I work in Oreilly corporate office. I was able to look up the return rate for BWD CSS51 and it is less than 2% so while some manufacturers may have issues, it appears that BWD does not. I'll try to install tonight and report results, but I'm pretty sure this will take care of it

 

BWD is one of the better aftermarket crank sensors, but I did help a couple of guys that had trouble with new BWD crank sensors in the past.

The thing that made the troubleshooting more difficult was that the sensor tested fine electrically, but the "spacing" of the sensor was a smidgen different than OEM and spacing is critical on a hall effect sensor like the crankshaft position sensor.

Good luck and keep us updated!

 

good point on the spacing. From what I've read I guess there's a spacer involved on some applications too. Just got the part, and it doesn't have a spacer so I would have to use the OE one, if there is one on a 93. The CSS51 is used on 93-96 years. I'll report when I attempt to replace tonight

 

new CPS and I'm back on the road. I'm wondering if I was getting a false 24 code now, since the new TPS has the same output at WOT as the old one did, just under 4 volts. oh well
I was surprised how easy the CPS was to install. I read of the nightmares on here, but it only took me 15 min. I had an extendable ratchet with a foldable handle though, that was perfect for the job. Only difficulty was trying to line the new bolts back in.
anyways, thanks for the advice on here