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Running Rich Misfire but only after driving hot

Tiny
ANGELA VARNER WATKINS
  • MEMBER
  • 2000 JEEP GRAND CHEROKEE
  • 4.0L
  • 6 CYL
  • 2WD
  • 220,000 MILES
I can crank up on a cool morning and it will run perfect and has fooled many shops and mechanic's ! I can leave the shop after getting it warmed up and having to sit in road construction at a idle. I can feel my car miss, then the rough idle starts. I opened my car door and it smells like un-burned gas and is smoking. I am sure because the gas is not being burned. I have actually had to pull over because when trying to proceed in traffic, it would not even pull off because of the flooded situation. Code came up, pulled into a shop and he said it was showing 0-2 sensor, but that was because it was running so rich. He did not think that is it. We have new plugs, coil pack, crank sensor, fuel filter, and the last shop yesterday put in a cam sensor. On the way home I broke down because it was missing so bad. Have not re-placed map sensor or 0/2 sensor. I Love my car, but I have an eight year old child and I might die in traffic, but I do not want my child to even ride with me. This is my family car and has been kept up well. Please help me. I cannot keep buying parts and paying shops and not even make it home!
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Friday, October 7th, 2016 AT 7:21 AM

16 Replies

Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Two things that I can think actually three, check for a vacuum leak like a hose bad cracked etc. check fuel pressure with a gauge auto parts rent it see link. finally check by the rear stud on engine for harness worn through and grounding out on block. if it is then show a mechanic and have them fix it and add conduit to it.
https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator
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Friday, October 7th, 2016 AT 12:18 PM
Tiny
ANGELA VARNER WATKINS
  • MEMBER
  • 15 POSTS
Thank you, but the mechanic at the shops we have taken it to have already checked the fuel pressure and they say our fuel pressure is good and fuel pump is working properly? I would have thought the mechanics would have checked for a vacuum leak, but maybe not? I will ask because it is sitting at a shop now ! The harness possibly being worn and grounding to the block, well this is a new one that we have not even considered? Last winter the heater core started leaking and we decided to invest in having the entire dash pulled out to re-place the heater core and I wonder if just maybe by some chance the harness got wedged between somehow, and caused it to rub and ground to the block? I also noticed a little sluggish start-up when I crank my vehicle so I had the battery tested and test was good, alternator is good, but have not checked starter? I wonder if this could have a dead drain on the battery too if the harness happened to be wedged and grounded by chance? We will check and post to let you know the results !
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Friday, October 7th, 2016 AT 2:39 PM
Tiny
ANGELA VARNER WATKINS
  • MEMBER
  • 15 POSTS
This is just a little amount of the frustration I have and I would be so "Happy' to have my vehicle back running with me not afraid to drive it!
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Friday, October 7th, 2016 AT 2:52 PM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
I know how you feel the dash thing normally does not interfere unless it is the ignition harness, but there has been a problem with what I described as far as running and a few other things. The vacuum leak would let it run but cause some of the problems you are experiencing.
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Friday, October 7th, 2016 AT 3:15 PM
Tiny
ANGELA VARNER WATKINS
  • MEMBER
  • 15 POSTS
Thank you! I will be in touch and maybe somehow I will get to drive my vehicle again enjoyable!
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Friday, October 7th, 2016 AT 4:08 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,643 POSTS
Please let us know what you find so it will help others.

Best, Ken
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Monday, October 10th, 2016 AT 10:05 PM
Tiny
ANGELA VARNER WATKINS
  • MEMBER
  • 15 POSTS
We have checked the things HMAC300 mentioned & those things checked out? I was told by my mechanic that I need a PCM (Computer) because until my car gets hot, it runs perfect then once it gets hot he believes a soldered area of my computer board is not making connection ! He drove it until hot then when it started acting up took it to the shop & put it on the computer & the readings were all over the place, nothing was reading as it should ! I hope this is right because the dealer prices to do this are outrageous. Basically 365.00 part(PCM), then another 190.00 to install & program ! I am going another route & hope I am not making a mistake? I am ordering a flashed & ready to install, set by my VIN# & Milege, PCM online by the most reputable company I can find (Rebuilt) not re-manufactured for around 225.00 & a core charge of 50.00 ! My mechanic said he can just pop it in & it should work! We will see?
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Tuesday, October 11th, 2016 AT 5:57 AM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
It may have a problem running as they cannot program the security in it. But glad you finally got it narrowed down.
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Tuesday, October 11th, 2016 AT 7:00 AM
Tiny
ANGELA VARNER WATKINS
  • MEMBER
  • 15 POSTS
Thanks HMAC300, I just found out when I was about to order the computer, the very thing you spoke of ! My husband read online to ask a few questions before ordering so I did ! I found out that the place I was buying the computer from was about to sell me a computer that would not work because my Jeep has the "Grey" key (Chip in it), and as they said (Anti-theft/Security) and I would need a locksmith to make me a key for that computer ! Of course I did not order the computer because in the area I live in the "Locksmith" is your dealer ! Oh well, I am trying one more thing before I go the dealer route ! I will keep you all posted ! I called the dealer & spoke with the mechanic there & he said he couldn't get to my Jeep for 3 weeks because he had 3 there now that he basically could not figure out & was questioning me about what parts I had already replaced & the symptoms of my Jeep? Couldn't believe this one ! He sounded as if he was understaffed & had to much to troubleshoot, but was very nice !
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Tuesday, October 11th, 2016 AT 3:18 PM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
He should check where I said on the stud at rear of engine that is quite a common problem with 4.0L engines. The wire wears through and causes all kinds of problem.S
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Tuesday, October 11th, 2016 AT 4:13 PM
Tiny
ANGELA VARNER WATKINS
  • MEMBER
  • 15 POSTS
Thank you, I will make sure this is checked !
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Tuesday, October 11th, 2016 AT 8:05 PM
Tiny
ANGELA VARNER WATKINS
  • MEMBER
  • 15 POSTS
I'm driving my Jeep locally & it runs like a brand new car ! It's just fooling me though, because if I head out very far it might quit? Boy I am dreading taking my Jeep to yet another shop Monday, but it has to be repaired so I can depend on it ! Wish it ran like this all the time?
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Wednesday, October 12th, 2016 AT 4:38 PM
Tiny
ANGELA VARNER WATKINS
  • MEMBER
  • 15 POSTS
HMAC300 & KEN, I thought I would post again on my latest ! Got my Jeep out of last shop yesterday: "No Computer" was put on it ! Mechanic did engine scan, found front O2 sensor dropping voltage indicating lean when engine was running rich. He replaced 02 sensor & reset fuel adaptives & cleared code ! This mechanic truly believes this was my problem ! It ran perfect home yesterday but it was about 45 min. Of driving & stopping ! I am praying my Jeep is done now but I can't help but be cautious, because so many times I left a shop with good thoughts & the problem not be solved? I will drive it & know in time if the issue was resolved ! Will post on my findings ! Thank you all !
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Saturday, October 22nd, 2016 AT 10:13 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,643 POSTS
Hey ANGELA,

That is good to hear, please use 2CarPros anytime we are here to help.

Best, Ken
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Saturday, October 22nd, 2016 AT 11:11 AM
Tiny
ANGELA VARNER WATKINS
  • MEMBER
  • 15 POSTS
I am driving my Jeep a round fairly locally & so far, no issues but I am still a little skeptical that an 02 sensor was my problem? I guess I should be "Happy" but I am listening for just one miss while I am driving ! I am so listening to everything that I notice my air condition compressor kick on & off & pay attention to how my transmission is shifting out ! I have even turned my radio down to the point I can actually hear problems, & in the past always played it so loud, I felt a problem long before I heard one ! Bahahahahha ! It's good to laugh a bit !
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Monday, October 31st, 2016 AT 5:18 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,643 POSTS
Yes it is, keep on eye on it so if you have any other problems start a new question, we are here to help.
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Monday, October 31st, 2016 AT 3:20 PM

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