Mechanics

JEEP CHEROKEE SENSOR PROBLEM

1999 Jeep Cherokee

Engine Mechanical problem
1999 Jeep Cherokee 6 cyl Four Wheel Drive Automatic 128000 miles

my 99 cherokee idles rough and hesitates during low speed driving and easy ecceleration, but if I punch it to the floor it takes off the way it should.I have replaced plugs, wires, cap button, idlecontrol and throttle position sensor. Fuel pump pressure is around 50 to 60 psi. What now?
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Wilee1
June 29, 2009.



OK so tell me what have you checked at this point? I see a list of parts that you have replaced and correct me if I am wrong but I understand that you replaced the cap, rotor, wires, plugs, idle speed motor, and throttle position sensor? Have tested the TPS to see if it is reading right? Have you checked the coolant temp sensor? How does the air filter look? Do you have a digital mutli meter so we can do a couple of test? Get back to me and we will go from there.

Racefan966
Jul 1, 2009.
Have not tested tps dont know how, also have not tested coolant sensor, air filter is brand new and I do not have a multi meter but can get one and use it if you tell me what and how to test it.

Tiny
Wilee1
Jul 1, 2009.
Ok you will need a digital multi meter, it don't need to be anything real expensive just one that works and has volts and ohm's. Once you have it I need you to unplug the coolant temp sensor and do an ohms test on the sensor (not the wire harness). Get back to me with the ohm's reading and if you do the temp when the jeep is cold then the temp at the time of the test too. Get back with that and we will test the tps next if needed.

Racefan966
Jul 2, 2009.
I tested the temp. Sensor it tested 13.85 ohms cold and.85 and continuosly dropping. If you want me test other things, just tell me what and how. THANK YOU!

Tiny
Wilee1
Jul 3, 2009.
Well the best I can find it looks like it is out of range, therefore I would replace it. Let me know how it goes.

Racefan966
Jul 6, 2009.
Why would the temp. Sensor cause the problem I am having? Iam just wondering.

Tiny
Wilee1
Jul 7, 2009.
Ok here is how it works. The coolant temp sensor provides information to the computer. With that information the computer will calculate injector pulse time and ignition timing. So when the Jeep is cold it causes a slightly richer fuel mix and higher idle. When it tells the computer the Jeep is at operating temp then the computer goes into what is called closed loop and with that it will use engine temp along with the map sensor and tps and cam and crank sensors to determine timing and fuel richness and injector pulse time. If the Jeep thinks it is colder then it really is this won't happen and it will use fixed information to try and run as it should.

Racefan966
Jul 7, 2009.
I replaced temp sensor and it did not make a difference. I checked with my part store and my idle air control and my throttle positioning sensor are both under warranty, so if I need to check either of them just let me know how.

Tiny
Wilee1
Jul 11, 2009.
Ok before I can walk you through any tests I need to know is it a Grand Cherokee or just a standard Cherokee and what is the 8th digit of the vin? Get back to me so I look up some tests. I would like to check the TPS and then the MAP Sensor. If it is the Grand Cherokee have you changed the fuel filter? Get back to me.

Racefan966
Jul 11, 2009.
It is just a standard cherokee, I personally would not own a Grand cherokee. The eighth number in the vin is x if you count from the end. Thank you for your quick reply.

Tiny
Wilee1
Jul 11, 2009.
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