Cris Engel
NAXJA Forum User
- Location
- East Wenatchee Wa
Good Afternoon
This is kind of a long story so please bear with me. I want to give all of you the best information I can provide. I bought a 2000 XJ with a 4.0 with 239xxx miles on it. The person I bought it from experienced a cracked 330 head in the classic location, but stopped driving it right away( So he said ). I was able to start the XJ and drive it onto the trailer. All in all it ran very well, even though I did not run it long enough to let it warm up because of the coolant traces I could see in the oil.
Fast forward a couple of weeks, I have it running with a new head 7120 casting.. Found out that there was more bearing damage done that I had first thought. I pulled the entire engine out and tore it down for a rebuild.
Fast forward another couple weeks and I have it back from the machine shop, installed and ready to run. After I perform my 30 min -2000 rpm cam break in, I turn it off, check for leaks and change the oil, and filter. Now I am ready to drive it, and here is where my issue begins. When the jeep is cold it start up and goes through its high idle to about 1800 for 10 seconds or so, then settles in to a very smooth 800 rpm idle. I can then rev it and it seems to increase engine speed fairly smoothly, but with a slight hesitation right at the first move of the throttle plate. As the engine warms up I start to notice a change in the smoothness, it sounds like it’s not firing all 5. If you go to the rear of the jeep you can hear it in the exhaust note. It is loping on 5. If I slowly increase the throttle, right at 2100 rpm the engine jumps up 500 rpm, and get very smooth. The same is true one decal; if I hold it up around 2500 and slowly drop it to 2100 it will start to miss. Things I have checked.
• New Plugs-
• Verified CPS
• Verified Cam Sensor
• Verified TPS 5v
Tonight I plan to use my mechanics stethoscope and list to each injector when it is missing to see if they are all working when warm. Any ideas or direction would be greatly helpful. I have performed all this work myself, so I can follow directions, and know my way around my jeep. I hope I have included enough info to allow you all to weigh in.
Thanks !
This is kind of a long story so please bear with me. I want to give all of you the best information I can provide. I bought a 2000 XJ with a 4.0 with 239xxx miles on it. The person I bought it from experienced a cracked 330 head in the classic location, but stopped driving it right away( So he said ). I was able to start the XJ and drive it onto the trailer. All in all it ran very well, even though I did not run it long enough to let it warm up because of the coolant traces I could see in the oil.
Fast forward a couple of weeks, I have it running with a new head 7120 casting.. Found out that there was more bearing damage done that I had first thought. I pulled the entire engine out and tore it down for a rebuild.
Fast forward another couple weeks and I have it back from the machine shop, installed and ready to run. After I perform my 30 min -2000 rpm cam break in, I turn it off, check for leaks and change the oil, and filter. Now I am ready to drive it, and here is where my issue begins. When the jeep is cold it start up and goes through its high idle to about 1800 for 10 seconds or so, then settles in to a very smooth 800 rpm idle. I can then rev it and it seems to increase engine speed fairly smoothly, but with a slight hesitation right at the first move of the throttle plate. As the engine warms up I start to notice a change in the smoothness, it sounds like it’s not firing all 5. If you go to the rear of the jeep you can hear it in the exhaust note. It is loping on 5. If I slowly increase the throttle, right at 2100 rpm the engine jumps up 500 rpm, and get very smooth. The same is true one decal; if I hold it up around 2500 and slowly drop it to 2100 it will start to miss. Things I have checked.
• New Plugs-
• Verified CPS
• Verified Cam Sensor
• Verified TPS 5v
Tonight I plan to use my mechanics stethoscope and list to each injector when it is missing to see if they are all working when warm. Any ideas or direction would be greatly helpful. I have performed all this work myself, so I can follow directions, and know my way around my jeep. I hope I have included enough info to allow you all to weigh in.
Thanks !