Missfiring renix.

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Dec 14, 2011 | 08:28 AM
  #1  
Went out to start my jeep this morning to discover that it's missing pretty bad. 1 or maybe two cylinders. I driver it daily and as of yesterday she was running great. It's been raining since yesterday. My question is this. Are there any sensors that can go bad and cause a misfire? My guess an I have to wait till after work is that my brand new ignition components are bad "let in water" and I need to replace them. I just want to cover everything before I toss money at her. It idles rough, tap the gas, the rpms drop. If you ease into the gas the rpms will rise but you can still feel the miss. I do smell gas out the exhaust pipe. All vacuum lines including the map are connected.
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Dec 14, 2011 | 02:54 PM
  #2  
I just got home and I'm uploading a video to youtube now. Here's what I've noticed now that it's light out. With the map sensor plugged in, she stumbles and dies as soon as you gas her. Black smoke comes out the tail pipe. When you unplug the map sensor *electrical plug* She idles up to 2k then dies, but does NOT misfire. It's like you're giving her gas, nice clean rev.
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Dec 14, 2011 | 03:07 PM
  #3  
Video. http://youtu.be/mqRrHiK58NM

Can they just go bad overnight? No warning at all.
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Dec 14, 2011 | 05:11 PM
  #4  
Quote: Video. http://youtu.be/mqRrHiK58NM

Can they just go bad overnight? No warning at all.
Yes, as they are electrical components.
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Dec 14, 2011 | 08:22 PM
  #5  
The map sensor seams to be working, black smoke out the exaust i'm thinking O2 sensor.
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Dec 14, 2011 | 08:41 PM
  #6  
Just to be sure, feel for vacuum with your finger on the line unplugged, at the Map. As I guess you might know, if the map isn't getting vacuum, (line plugged, cracked), it will run rich. Easy enough to be sure.
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Dec 14, 2011 | 09:08 PM
  #7  
A bad O2 sensor won't make it run pig-rich and miss. The ECU goes into a default/predetermined mixture mode when an O2 sensor fails.
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Dec 14, 2011 | 09:22 PM
  #8  
Had the same problem and it was a small hole in the vacuum line going to the map sensor.
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Dec 14, 2011 | 09:38 PM
  #9  
check the plug that the MAP line goes into at the back of the throttle body it can also crack and leak
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Dec 15, 2011 | 03:56 AM
  #10  
akita8 and highmileage offer some good advice. A slight to medium leak in that hose could cause your problem. Unplugging the MAP just floods the crap out of it and it dies quickly. I wouldn't overlook this.
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Dec 15, 2011 | 07:41 AM
  #11  
I'm getting vacuum. That was the first thing I checked. I have to replace the electrical connector. The ground keeps wiggling out of the connector. I also have a new map sensor as well. Wish me luck!
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Dec 15, 2011 | 04:06 PM
  #12  
Another video. http://youtu.be/v65ACWaOIF4

Another thing as well. After the jeep is warm, and you have the CTS plugged in. The jeep will not start. It will crank and crank, and you will smell fuel. Unplug the sensor, and she'll fire right up. I've never heard of a CTS causing a no start.
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Dec 15, 2011 | 04:08 PM
  #13  
Did you ever do the sensor ground test in the beginning of my TPS write-up?
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Dec 15, 2011 | 04:14 PM
  #14  
Yes, and the grounds are still testing out fine. I re tested today after I got home.
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Dec 15, 2011 | 04:16 PM
  #15  
Have you tested the CTS?
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