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Rough idle poor acceleration stumble at cruise

Tiny
ERICRAZ
  • MEMBER
  • 2004 JEEP LIBERTY
  • 3.7L
  • 6 CYL
  • 4WD
  • 160,000 MILES
Running poor at an idle a loping idle to try to clarify, steady putt putt putt, big hesitation off the line as if I am not even hitting the throttle but then catches and gets moving then when at a cruise speed and lightly push throttle getting a stuttering like a vibration. Let up slightly or throttle harder will stop. Also hesitation when powering out of a slow corner (turning onto a different street.) No CEL (check engine light).
Was CEL when issue suddenly occurred. Random misfire (P0300)misfire number two cylinder (P0302). Changed out all 6 coils and plugs cleared codes. Ran the same but after short drive threw P0159 code. Bad O2: sensor. Changed both inboard O2 sensors. Cleared codes. Ran a bit better but not much change. Out for another test drive ran basically the same. Now no codes what so ever. Fuel delivery system checks out fine. Just cannot figure this out. Help please.
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Sunday, August 19th, 2018 AT 1:06 PM

19 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good afternoon.

The first thing I would do is a compression test on number two cylinder to be sure there is no issue internally in the motor.

The 300 code indicates it may be running lean from low fuel pressure. I would check the fuel pressure.

As far as the 159, I would not have replaced the sensors at all. That code may be from the misfire you have.

P0159
Descriptor
O2 Sensor 2/2 Slow Response
Probable Causes
Exhaust Leak
Good Trip Counter Equal to Zero
Oxygen (O2) Sensor
Oxygen Sensor (O2S) Return Circuit
Oxygen Sensor (O2S) Signal Circuit

300 code

SYMPTOM
P0300-MULTIPLE CYLINDER MISFIRE

WHEN MONITORED
Any time the engine is running, and the adaptive numerator has been successfully updated.

SET CONDITION
When more than a 2% (2.5% LEV) misfire rate is measured during two trips. Above 3000 RPM 1 trip less than 3000 RPM 2 trip.

POSSIBLE CAUSES
- Intermittent misfire
- Visual inspection
- (A142) ASD relay output circuit
- Engine mechanical problem
- Ignition coil
- Coil control circuit
- Spark plug
- Checking fuel pressure
- Fuel pump inlet strainer plugged
- Restricted fuel supply line
- Fuel pump module
- Checking fuel leak down
- Fuel injector
- Injector control circuit
- PCM

302

P0302
Descriptor
Cylinder No.2 Misfire
Probable Causes
Automatic Shut Down (ASD) Relay Ouput Circuit
Coil Control Circuit
Engine Mechanical Problem
Fuel Injector
Fuel Leaks Down
Fuel Pressure
Fuel Pump
Fuel Pump Strainer
Fuel Supply Line Restricted
Ignition Coil
Injector Control Circuit
Intermittent Misfire
Powertrain Control Module (PCM)
Spark Plug
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Sunday, August 19th, 2018 AT 1:14 PM
Tiny
ERICRAZ
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  • 13 POSTS
Okay. Fuel pressure seems okay. I have received p0175 when I went through the "plug wires" while running checking for any other "bad" cylinders. I assume that would be normal considering I turned off spark on multiple cylinders and pumped raw fuel through the system. Cleared that code and has not come back. I do get some white smoke from the exhaust on occasion. Cold start seems the worst. That still would be an indication of rich mix is it not? Compression appears okay, 130 to 145 every cylinder. Also the stutter seems to be only at idle and under light load.
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Sunday, August 19th, 2018 AT 1:50 PM
Tiny
ASEMASTER6371
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Okay, what is the fuel pressure?

If you have white smoke, that is coolant burning which will lean out the mixture.

Does it still run rough?

Roy
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Sunday, August 19th, 2018 AT 1:58 PM
Tiny
ERICRAZ
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  • 13 POSTS
Actually more a light blue. Coolant level has not changed at all no oil in water or visa versa. Do not have a pressure tester but when I hit the release on the fuel rail it shoots a really good stream for a second. Hit the key and get an immediate start and get the same release of pressure after I shut it down. Do not know if this matters but getting poor gas mileage also.
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Sunday, August 19th, 2018 AT 2:24 PM
Tiny
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I would still have the test done to confirm.

If you have the flip yop, I would replace it with the correct cap. The cap does not have the flip yop as it is a closed system.

Roy
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Sunday, August 19th, 2018 AT 2:30 PM
Tiny
ERICRAZ
  • MEMBER
  • 13 POSTS
I have also heard these engines have an issue with the rocker arms popping off the push rods. Could this be a possibility?
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Sunday, August 19th, 2018 AT 2:34 PM
Tiny
ASEMASTER6371
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Yes, they do as well as exhaust valve seat issues in the cylinder head.

A compression test will tell this if it was the issue.

Roy
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Sunday, August 19th, 2018 AT 2:37 PM
Tiny
ERICRAZ
  • MEMBER
  • 13 POSTS
Not sure what you mean by a flip yop. Two fuel rails with a cross over and a release valve that looks like a tire stem.
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Sunday, August 19th, 2018 AT 2:38 PM
Tiny
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Are you referring to the fuel pressure?

I was referring to the radiator pressure cap on the surge tank line.

Roy
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Sunday, August 19th, 2018 AT 2:41 PM
Tiny
ERICRAZ
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  • 13 POSTS
Compression check is fine as stated above. Basically 130 all cylinders.
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Sunday, August 19th, 2018 AT 2:42 PM
Tiny
ERICRAZ
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  • 13 POSTS
Being fuel injection it will not have intake valves correct? Only exhaust.
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+1
Sunday, August 19th, 2018 AT 2:44 PM
Tiny
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130 is actually low. It should be around 150.

The minimum is 100 but it would be a poor running engine if it were that low.

Are you referring to the fuel pressure?

I was referring to the radiator pressure cap on the surge tank line
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Sunday, August 19th, 2018 AT 2:47 PM
Tiny
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No, it has intake valves. The fuel injectors inject fuel into the intake manifold right by the intake valve.

Roy
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Sunday, August 19th, 2018 AT 2:52 PM
Tiny
ERICRAZ
  • MEMBER
  • 13 POSTS
Yes, I was referring to fuel pressure. Okay now I have a new observation. Pulled plugs again. Number two does not seem to be firing. Plug is wet with fuel. Second time this occurred. Changed out the new coil with the old check for spark got a really pretty blue. Replaced plug and old coil (new coil nothing) ran okay for a second then back to its tricks. Checked it again wet with fuel. Did the same again. Got pretty blue. Short drive ran good for a few then back to bad and wet plug again. WTH?
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Sunday, August 19th, 2018 AT 3:37 PM
Tiny
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Sounds like the injector is not closing all the way. It may have debris on the pindle and is constantly dripping.

Roy
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Sunday, August 19th, 2018 AT 3:44 PM
Tiny
ERICRAZ
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Why would that cause me to lose spark? Would the computer just shut it down?
BTW. Thank you for your time and answers!
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Sunday, August 19th, 2018 AT 3:50 PM
Tiny
ASEMASTER6371
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You are welcome.

You never said you lost spark? When did that happen?

Roy
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Sunday, August 19th, 2018 AT 3:56 PM
Tiny
ERICRAZ
  • MEMBER
  • 13 POSTS
Noticed playing with it today. My first code told me number two was the issue. When I first addressed the issue I changed the coil and plug (as well as the other five while I was at it probably overdue) fixed it very temporarily as it is doing now. Number two plug was shot. Other plugs were "okay" but looked over due also. That being said the issue keeps coming up as number two. Was wet and as I said shot when I first pulled it. Now third coil on it and the plug keeps coming out wet and not looking "used" hardly and does not spark again until I change the coil. Hmm?
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Sunday, August 19th, 2018 AT 4:15 PM
Tiny
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Seems like the spark keeps getting shut down by the computer.
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Sunday, August 19th, 2018 AT 9:20 PM

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