Engine problems bucking, loss of power?

Tiny
JAMESDUPONT
  • MEMBER
  • 2001 JEEP CHEROKEE
  • 4.0L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 265,000 MILES
Be running great then goes to crap. Suddenly when u accel, she'll break down bucking, loss of power, motor be misfiring, and will vibrate. Next day she good for awhile then goes back to crapping out. Then later all good again. Have new fuel injectors, spark plugs and rail, replaced throttle position sensor, maps heat sensor, have checked several times for vaccun leaks, replaced trans mount, u joints, replaced main cat, when run codes, one time nothing, then next day misfire on 3, next day it'll show throttle position sensor which a new one had been put earlier that which at that time ran great for 50 miles then crapped. This has cost me money, time, not having transportation, stress and down right ugly. This jeep has ran great and does not even burn any oil. I need help finding problem
Friday, January 9th, 2026 AT 7:26 AM

12 Replies

Tiny
KEN L
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I have seen big problems with the crankshaft angle sensor going bad which will cause these problems will no codes, there is a slight chance the fuel pump is going out as well but the crankshaft sensor is easier and cheaper. Also, make sure the battery ground-to-chassis cable (smaller) is good and connected. Here is the location of the sensor which is I on the transmission bellhousing on the driver side, I would swap it out first. Check out the images (below). Please upload an image or a short video in your response, so I can see what's going on. Ken
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Friday, January 9th, 2026 AT 10:34 AM
Tiny
JAMESDUPONT
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Replaced crankshaft position sensor, nope that didn't help. It is a hard place to get to and switch out. I since ordered a camshaft position sensor and will get it Tuesday. There aren't any more parts for me to replace after I put in camsensor. Will let u know.
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Friday, January 23rd, 2026 AT 4:49 PM
Tiny
KEN L
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Yep, these problems are difficult for sure, try to run the codes again, I have seen the PCM, fuel pump and relay or ignition switch start to go out and cause this as well. We need to isolate which system is failing, ignition or fuel. When it stall please go over this video to get a clue on what is going on.

https://www.youtube.com/watch?v=lXLJbuAZ4CE

Please let us know what happens. Ken
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Saturday, January 24th, 2026 AT 10:52 AM
Tiny
JAMESDUPONT
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  • 7 POSTS
My jeep does not stall and it does start every time. It usually runs good for the first 20 minutes then it's like it jumps timing and starts misfiring, vibrate, and cuts out when trying to get more power for speed or up hills. I have replaced these parts with new. Spark plugs and coil rail, injectors, maps, throttle body sensor, tranny mount, u joints, crankshaft position sensor, heat sensor located near maps, have physically check for vaccun lines leaks along with a spray that will make the motor rev higher if it hits a vacuum leak. Checked and rechecked electrical plug ins, wires and connections. Took off main cat, inspected and was not plugged. I have not taken off the 2 mini cats coming from manifold and then the two pipes comes together in a y connection and becomes one exhaust line going to main cat then muffler to tail pipe. I've ordered a camshaft position sensor to replace old one. Should be delivered any day. If that doesn't work, I'm at a lost what to do. I've done a hard reboot twice. If the pcm is bad, would it throw codes of plug misfires or would it cause the issue I'm currently having. I've spent couple of months on this and put good bit of money in it, all that I wouldn't mind, if it would cure the problem and run normal again. I love this jeep, it does not burn a drop of oil, almost mint condition, has absolutely no rust underneath or any where else. I have kept it very clean ', even the motor. Before this problem started, I had strangers walk up to me and jeep, and out rite offer me 7000, 8000 as is, without even taking it for a drive. I wouldn't sell, but now I wish I had cause now it's worth nothing. No one can figure out the why.
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Monday, January 26th, 2026 AT 4:34 PM
Tiny
KEN L
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So when it stops running, we need to see which system is failing, ignition or fuel. Do you have any codes when you run them?

https://www.youtube.com/watch?v=LBCpCWEFnTg

To me it sounds like the fuel pump or FP relay is failing.
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Tuesday, January 27th, 2026 AT 9:03 AM
Tiny
JAMESDUPONT
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Codes for crankshaft position sensor, 30 minutes after I put in a new one, misfires 3, 5, 6 cylinders, when it's been sitting for hours and engine is cold, no codes come up, not even the recent history codes. After driving for anywhere between 20 minutes to 40 minutes, it jumps to limp mode again. Car will always start, no back firing and plenty of power, no misfires for that length of time I mentioned. When in limp mode, power breaks down when hit 2800 rpm, vibrates, cuts out when trying to recover power. Have to slowly get back to speed by continuing to off on accel.
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Friday, January 30th, 2026 AT 11:23 AM
Tiny
KEN L
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What codes are they, also did you use an OEM sensor? Some after market sensors are cheap and don't the job correctly.
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Saturday, January 31st, 2026 AT 8:56 AM
Tiny
JAMESDUPONT
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I put on new camshaft position sensor. Motor running better, doesn't break down at 3 grand, has good power. But still having some ruff idle, car don't want to start easy no more. Code reading PO304, #4 not getting proper mix. Going to tear into 4 plug cylinder right now
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Tuesday, February 3rd, 2026 AT 12:14 PM
Tiny
JAMESDUPONT
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#4 plug the end was bent fwd and over firing pin almost touching. Straighting and put in #5 spot and 5 into 4 spot. I have just checked twice on the codes. It' can't be right, 9 codes! P0 304, 355, 351, 353,303,300, 455, P0172 1391, 1389. That's everything, that's not possible is it? It started up good and motor sounds good. I apparently don't know jack about cars. Car gets worst Everytime a repair or part replacement happens.
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Tuesday, February 3rd, 2026 AT 1:55 PM
Tiny
KEN L
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So is this a new problem or do we still have the same problem. if this is a new issue please copy this text and start a new thread. We only handle one problem per thread, please post your new question here, you must be logged in.

https://www.2carpros.com/questions/new

Cheers, Ken
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Tuesday, February 3rd, 2026 AT 3:51 PM
Tiny
JAMESDUPONT
  • MEMBER
  • 7 POSTS
Same problem, misfires, loses power when going up hill. Vibrates cuts out at 3granld rpm. After putting in new cam sensor and code po304 came up, I took out #4 plug, regauged straighten a bit put in #5 hole and 5 inton#4 cylinder. When I ran it, code po304 still came up and 8 more codes. Could it be my mother board faulty?
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Friday, February 6th, 2026 AT 3:02 PM
Tiny
KEN L
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Yep, that is what it sounds like with all of those codes, I would use these guys and get a rebuilt PCM. But first, double check the fuel pressure and check the spark plugs. This video can show you how to do the fuel pressure,

https://www.youtube.com/watch?v=kgEixCsqcYM

339 kpa +/- 34 kpa (49.2 +/- 5 psi) psi

https://www.flashmastersecm.com/

Let us know how it goes.
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Saturday, February 7th, 2026 AT 9:03 AM

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