I have reached a head banging point

Here is the problem and I am running out of ideas, cash, and patience.

I came out of work last Thursday and went to start her up and she would not turn over. She had juice so the battery was not dead. It cranks like it is about to, but just wont catch.

I had the Jeep taken home, and checked the computer for codes but got none. Here is what I have tested and replaced.

- Fuel pressure tested off the fuel rail, and came out to 47 psi
- If I turn the car on I can hear the fuel pump kick on
- All Fuses and relays checked
- Replaced both up-stream and down-stream oxygen sensors
- Replaced Spark Plugs
- Replaced cap and Distributor Cap & Rotor
- Replaced crankshaft position sensor
- Replaced Ignition coil

This is where I am at. If I crank the car and put my foot on the gas I can get her to hold idle after about thirty seconds. If I don't hold the gas I cant get her to turn over. Any ideas welcomed.

 

is it possible the distributor moved and your timing is now way out?

 

have you checked for code

 

What year? iPhone doesn't show any info!
Could be TPS? It sucks your not getting a code to pop up.. I wonder about the timing, too. How does it run once started? Does it?? The stuff you changed is all right in line with your issue... I know you said you checked fuses/relays, etc., but did you check voltage anywhere to make sure spark isn't getting lost?

 

The Jeep is a 1999 Cherokee Sport 4.0L 6cyl 4wd. Checked it a couple times for codes absolutely none. When the Jeep does hold idle it runs normal. I didn't check the volts anywhere yet. I have had two people tell me its the TPS. Is there anyway I could check that without going out and replacing it? I learn how to work on the Jeep as I go so I am still semi new.

 

popst number 5 on here http://www.jeepforum.com/forum/f11/how-test-tps-610386/

 

Ask tjwalker about TPS- dudes got the info! Theres another thread that covers this in here that's active... Hang on I'll find it..

 

Here! This is taken directly from tjwalkers post: (thanks, btw!!)

For your issue, you MUST rule a faulty throttle position sensor in or out early in the troubleshooting process. The TPS is directly involved in shifting characteristics of the AW4 transmission. Oh, and then there is this about the TPS: THEY HATE WATER! Test and or replace it before looking elsewhere; my gut instinct is that this could be the culprit here after your water crossing.
---------------------------------------

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!

o 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".
o 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.
o 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.
o 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.
o 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.

 

Thank you so much for the info, I am going to go through that today and see where I stand hopefully fingers crossed it fixes the problem. Any other ideas besides the TPS? Do you think its the fuel pump by any chance?

 

Checked the TPS and it came out fine. Any other guesses?

 

Success!

I decided to replace the TPS just for laughs, and the problem was fixed. Thank you again for pointing me in the right direction.