2003 Other Jeep Models knocking/pinging when cold and rough

Tiny
JEEPSTER2003
  • MEMBER
  • 2003 JEEP
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 122,000 MILES
When the jeep is started in cold weather it will make a slight knocking noise until the coolant temp hits around 180. After it warms up the noise goes away. Then the jeep idles rough when in drive, but not so much when in park or neutral. I have noticed recently a faint noise when accelerating that sounds like something vibrating in the glove box, but there is nothing in there. So far I have changed the spark plugs, 02 sensors, checked all vacuum lines, cleaned the throttle body, cleaned idle speed motor, hooked the car up to a scan tool (no error codes). I have put a tank full of mid grade fuel in and it seemed to reduce the engine noise but my performance has not improved. During this time my mpg has dropped from 25-27 to 19-22. Please help.
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Sunday, December 7th, 2008 AT 11:57 AM

15 Replies

Tiny
RACEFAN966
  • EXPERT
Ok I need you to do some testing. So you will need a digital multi meter. Now if you would unplug the coolant temp sensor (not sender) and do an ohm's test on the sensor (not the harness) and if you do this cold then you can give the air temp at the time of the test with the ohm reading and I will see if it is in spec. Lets start there and see where we need to go from there. Now some questions, when was the last tune up done? When was the fuel filter replaced last (only on grand cherokee's). How is the air filter and how are the boots on the coil pack? Get back to me and we will go from there.
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Thursday, March 12th, 2009 AT 10:37 AM
Tiny
JEEPSTER2003
  • MEMBER
Racefan966,
I went out and checked the cooland temp sensor and got a reading of 32.90 on a 40K ohm scale. My Jeep only has 1 coolant temp sensor for both the temp sensor and sender for the gauge. I believe the temp outside was about 30 degrees. I also took a reading for the air charge sensor which is the same sensor part number and it was 32.59 on a 40K scale.
In the past month I have changed the air charge sensor, map sensor, TPS, Fuel Filter/regulator, and spark plugs. I changed the ignition coil rail (which comes with the boots on it) about a year ago at 95,000 miles. The air filter gets changed every oil change (3,500 miles).

Thanks for the help, this jeep is driving me crazy.
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Saturday, March 14th, 2009 AT 8:46 AM
Tiny
RACEFAN966
  • EXPERT
Ok just to go over a few basics here. Have you checked the fuel pressure? Have you checked for vacuum leaks including the intake manifold and throttle body area? Have you checked the idle speed control motor? Have you checked the EVAP system for any broken vacuum lines to it? How is the fuel economy? As for the sensor is looks like it is bad but this may not be a 100% fix just so you know.
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Saturday, March 14th, 2009 AT 8:18 PM
Tiny
JEEPSTER2003
  • MEMBER
When I check the fuel pressure a month ago, I found it to be 60psi. So I changed the filter/regulator with a factory filter and this corrected the pressure to 50 psi.
I looked for vac leaks around the intake and throttle body and could not find any. And all the other vac lines are good.
I took the throttle body off and cleaned it about the same time as the filter change. At that time I looked at the idle speed motor. I t was a little dirty so I delicately cleaned it and reassembled the throttle body with a new gasket. I am not sure how I can test the idle speed motor, it is not showing a fault code for it.
The EVAP system lines show no cracks in them, and the scan too I used last time said the EVAP system test passed. I assume the system is OK.
The fuel economy is still 5 mpgs lower than where it usually is.
What temp is the existing sensor reflecting with a value of 32.90 40k ohm scale? How can that sensor be wrong when the air charge sensor is the same part number with almost the same reading?
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Tuesday, March 17th, 2009 AT 9:13 PM
Tiny
RACEFAN966
  • EXPERT
They are not the same who ever told you that was wrong. The temp sensor is in a water jacket and the air charge temp sensor is in the intake system they can't be the same and if they are that is your problem. The air charge temp sensor is Napa pt# TS3004 and the coolant temp sensor is Napa pt# TS3005. Here are the pic of them both the first is the air charge temp and the second is the coolant temp sensor. If you have the same part number in both spots then this causing a lot of problems if not all of them. Let me know ok. If not then replace the coolant temp sensor so that it will be working right but keep in mind this may not fix everything. If all is good here then we will check the Idle air control valve next ok. Here is the pics.

This is the Air Charge Temp Sensor.


http://www.2carpros.com/forum/automotive_pictures/249564_276510_1.jpg



this is the coolant temp sensor


http://www.2carpros.com/forum/automotive_pictures/249564_396291_1.jpg

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Wednesday, March 18th, 2009 AT 10:22 AM
Tiny
JEEPSTER2003
  • MEMBER
Thanks for the info on the sensors. The local autozone had both sensors with the same part number. I bought the correct sensor and installed it. I noticed a slightly better idle but it is still rough when placed in gear. I did notice that after the sensor was changed that the temp gauge runs in the middle now (about 210) in stop and go traffic. I don't know if that means anything or not.
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Monday, March 23rd, 2009 AT 9:39 AM
Tiny
RACEFAN966
  • EXPERT
No around 210 is normal my jeep runs there too. So anyway I do think we should check the cam or crank sensor. How old are the boil on boot ends and the spark plugs.
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Monday, March 23rd, 2009 AT 2:51 PM
Tiny
JEEPSTER2003
  • MEMBER
Racefan966,
I recently replaced the crank sensor to try and remedy my current problem with no luck.
Boil on boot ends? Are you refering to the sparkplug boots?

I changed the plugs about month ago with original stock plugs. I tried platniums and they did not help, so I went back to standard auotlite plugs.

I changed the ignition coil rail (which comes with the boots on it) about a year ago at 95,000 miles. So the rail and boots have roughly 25k-30k miles on them.
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Monday, March 23rd, 2009 AT 3:09 PM
Tiny
RACEFAN966
  • EXPERT
Lets check the knock sensor this sensor is what determines the amount of timing by detecting a knock in the engine. SO first unplug it and then turn the key on engine off. Make sure that one of the wires has more then 2 volts. Now if that is good then turn the key off and now check the term of the sensor to ground it should be less then 100 ohms if more then the sensor is no good.
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Tuesday, March 24th, 2009 AT 9:59 AM
Tiny
JEEPSTER2003
  • MEMBER
Racefan966,
I have tried looking for this sensor in the past. It seems the 2003 grand cherokee (calif. Emmisions) does not have one. I have looked it up on autozone and they do not even list one for my model. I have had other model jeeps with the I-6, and this 03 model I-6 does not have a knock sensor or EGR valve.
Weird isn't it?
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Tuesday, March 24th, 2009 AT 12:54 PM
Tiny
RACEFAN966
  • EXPERT
Ok it seems that the 6 cyl don't use one it uses the map sensor with cam and crank sensor. So if you haven't done it yet I would say lets test the map sensor. (Be lucky you don't have one as the V8 has 2 under the intake). Anyway here is the test.
The sensor is next to the throttle body it has a wire harness pluged into it and a vacuum line as well.
Make sure the vacuum line is not cracked then do the following.
First disconnect the harnes to the sensor. With key on engine off check to make sure the orange wire has 5 volts. If not then repair the wire.
If I can tell right the dk green wire with the red stripe is the reference wire so with that plug the sensor back in. Back probe that wire with a paper clip and hook your meter to it. With the key on engine off if the voltage is more then 1.2 volts the sensor is no good. Let me know what happens here as the map sensor is used to determine the timing needed.
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Tuesday, March 24th, 2009 AT 8:20 PM
Tiny
JEEPSTER2003
  • MEMBER
I checked the MAP sensor today and I do have the supply voltage of 5 volts and the signal wire shows about 1 volt. I even checked the MAP I changed a month ago and it has the same readings. I guess I have a spare now.
For future reference I also changed the crank position sensor in Feb for my sanity. I was reading alot of posts on how this sensor seems to fail at about 100K. I figured it is a daily commuter vehicle so I changed it. What a pain.
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Thursday, March 26th, 2009 AT 10:12 PM
Tiny
RACEFAN966
  • EXPERT
Ok where the distributor would be there is a camshaft sensor there. I need you to unplug it and make sure there is 5 volts getting to it. Then make sure with the ohms setting that the ground is good in the harness too. Here is a pic of the harness and what wire does what. If this is good then we will check the signal wire to make sure that the signal is correct ok. If this checkes out then we will move to the knock sensor.


http://www.2carpros.com/forum/automotive_pictures/249564_Graphic_56.jpg

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Friday, March 27th, 2009 AT 10:34 AM
Tiny
JEEPSTER2003
  • MEMBER
Checked the camshaft sensor.
Here are the results.


https://www.2carpros.com/images/question_images/199241/original.jpg


Sensor voltage key on engine off


https://www.2carpros.com/images/question_images/199242/original.jpg


Ground Ohms ignition off key off


https://www.2carpros.com/images/question_images/199243/original.jpg


Key on engine off

This video is the sensor signal wire with it running
http://www.youtube.com/watch?v=wwAlcLdYdVQ

In your last post you said if this is OK we are going to look at the knock sensor.......but i do not have one.
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Friday, March 27th, 2009 AT 2:27 PM
Tiny
RACEFAN966
  • EXPERT
Ok with all I can find what all you have already done it is leading back to the cam sensor. It should have steady readings not fluctuating. I am aprehensive about replacing it as you have spent lots of money already but nothing else makes sense with all that has been done and what the tests say at this point. Let me know how it goes.
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Sunday, March 29th, 2009 AT 9:50 AM

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