Runs rough

Tiny
JEFF HERMAN
  • MEMBER
  • 2006 JEEP LIBERTY
  • 3.7L
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 160,000 MILES
Engine codes multiple cylinder misfire. Cylinders 2, 4, 6 plugs are carbon fouled. Tested primary coils okay. Did a cylinder drop down test 135 firing 246 not I think due to carbon filed plugs. Other codes were AIT input too high. I believe the other one had to do with throttle air sensor or something idle air sensor maybe. The only thing I can see is a cracked valve cover vent tube that's supposed to be about a half inch ID and it's patched together with a piece of quarter inch fuel line so it's restricted. I don't know if this has a bearing on anything. When the car is running all coils are getting a voltage pulse to fire. Going to test reference voltage of the AIT and check it for functioning. Any other ideas would be greatly appreciated. Engine will not rev over 4,000 RPMs and then follows the plugs installs after several times.
Friday, April 16th, 2021 AT 10:02 PM

36 Replies

Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Just need to clarify the issue a little.

You are replacing the spark plugs and then after you drive for a short time, they are fouled again?

If this is the case then we have too much fuel on that bank or it is just unburned fuel. So I would suggest starting with compression check and go from there unless that is what you did when you say a cylinder drop test.

https://www.2carpros.com/articles/how-to-test-engine-compression

If this is the case and you have 135 on all 3 then that is the issue. That is too low as it should be at least 170 on this engine.

If that is the case then we need to do a cylinder leakage test to find out where we are losing compression but I am thinking we have a cam issue.

Let us know and we can go from there.
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Saturday, April 17th, 2021 AT 7:22 PM
Tiny
JEFF HERMAN
  • MEMBER
  • 444 POSTS
No not driving a little they fall out right away just revving it up a couple times in the driveway. I thought about doing a compression test all I did was with the engine running disconnect the power to each coil and listen for an RPM change. I replaced the AIT sensor as that was one of the codes and I tested the sensor plug and it was good and I tested the sensor and it seemed to have faulty readings.
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Saturday, April 17th, 2021 AT 7:43 PM
Tiny
JEFF HERMAN
  • MEMBER
  • 444 POSTS
I put in the cleaned up spark plugs and the new AIT sensor and it fired right up and idled at 1000. Then I did the cylinder drop down test where I disconnect the power to each coil individually and listen for an RPM change. Cylinders one three and five reacted. Cylinders two four and six had no change in RPM when power was disconnected to the coil indicating that they are not firing. I will include the codes that came up. P2305, p2311, p2317, po300 pending, p2305 pending, p2311 pending, p2317 pending. Seven codes in all. The engine would not rev beyond 4,000 RPMs and then started to fall out again. Not driving revving in the driveway and then reading codes. Compression was 150 PSI on both Banks so I'm not concerned that the compression is weak it was a cold test. What about the ECM being bad or a plugged catalytic converter? This should give you something to work with and I appreciate your assistance. Thank you.
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Sunday, April 18th, 2021 AT 10:32 AM
Tiny
NICKOLAOSF
  • MECHANIC
  • 69 POSTS
Hi Jeff Herman,

First you will need to repair all plastics tubes that are cracked or broken, you are creating a pressure leak with the positive crank ventilation. that the computer will try to compensate for vacuum leak.
second test fuel injector continuity at the connector with the injector to verify continuity. (see link)

https://www.2carpros.com/articles/how-to-test-a-fuel-injector

After you test injector electrical continuity erase codes from system, check to make sure you have no air leaks or vacuum related. notice attention on the one side cylinders 2,4,6 these are on one side.
Please run down these guides and report back.
when you erase codes read again to verify and report codes.
as for the coils you can swap one at a time from other side of bank from cylinders 1,3 and 5.
I am glad to help you, If there is anything else we can help you with please contact us again. Thank you for choosing 2CarPros

Cheers, Nick
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Sunday, April 18th, 2021 AT 12:22 PM
Tiny
JEFF HERMAN
  • MEMBER
  • 444 POSTS
Here's the update on the Liberty. All injectors are clicking, all have power supply, all have pulse. Have not been able to remove connectors to test individual resistance on each injector or gotten around to checking spray pattern. All six coils have spark. Repaired leaks in the breather tube with a fabricated tee. Latest code read was PO300. Still no response on 2, 4 or 6 when coil is disconnected. Need to check resistance of those three injectors possibly they are bad. Thank you for your assistance let me know what you think and where we go next.
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Monday, April 19th, 2021 AT 2:00 PM
Tiny
NICKOLAOSF
  • MECHANIC
  • 69 POSTS
If you repaired leaks and have cleared codes and after running you get p0300 multiple misfires. The next step is to swap if possible coils with others clear memory and rescan.
Cheers, Nick
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Monday, April 19th, 2021 AT 2:22 PM
Tiny
JEFF HERMAN
  • MEMBER
  • 444 POSTS
Would this be in the secondary windings?
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Monday, April 19th, 2021 AT 2:41 PM
Tiny
JEFF HERMAN
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  • 444 POSTS
Can you swap the coils one at a time with a known good one brand new?
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Monday, April 19th, 2021 AT 2:45 PM
Tiny
NICKOLAOSF
  • MECHANIC
  • 69 POSTS
Yes you can I think they are all the same you can swap cylinder 1 with cylinder 2 and so on when you rescan it will give you codes for other side.
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Monday, April 19th, 2021 AT 2:59 PM
Tiny
JEFF HERMAN
  • MEMBER
  • 444 POSTS
First I want to get a resistance reading on injectors two four and six.
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Monday, April 19th, 2021 AT 3:07 PM
Tiny
JEFF HERMAN
  • MEMBER
  • 444 POSTS
Why would there be no change in RPMs if I have spark in those cylinders? Is that an indication there's no fuel even though there's fire? Those plugs are sooty black.
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Monday, April 19th, 2021 AT 3:08 PM
Tiny
NICKOLAOSF
  • MECHANIC
  • 69 POSTS
If the plugs are wet of fuel that means there is no spark, that is why I recommend swapping to see what is the other side going to do.
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Monday, April 19th, 2021 AT 3:16 PM
Tiny
JEFF HERMAN
  • MEMBER
  • 444 POSTS
Before I fix the air leak the plugs on one side were almost white and on the other side were dry carbon black. Not wet filled with fuel. After I fixed the leak cylinders to four and six are still carbon black and one three and five are starting to run richer. I have to do some more testing especially on those three injectors check the resistance won't get around to that until tomorrow as it's 35° out here now again.
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Monday, April 19th, 2021 AT 3:55 PM
Tiny
JEFF HERMAN
  • MEMBER
  • 444 POSTS
Good afternoon. All the injectors measure 10.3 ohms I took them out and cleaned them but was not able to test a spray pattern but I swapped the three no one working ones to the other side cylinders two four and six. There is also quite a bit of oil buildup inside the plenum. I'm including pictures of that and some discoloration on the injector connectors but it's on both sides even the working one.
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Tuesday, April 20th, 2021 AT 11:01 AM
Tiny
JEFF HERMAN
  • MEMBER
  • 444 POSTS
My internet is down and it takes forever to send any pictures so I'm going to clean the plenum and try to read codes if it runs.
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Tuesday, April 20th, 2021 AT 11:02 AM
Tiny
JEFF HERMAN
  • MEMBER
  • 444 POSTS
Update: I put everything back together ran it and got codes for secondary circuit in coils b d and f. Cleared the codes ran it again and all I got was multiple cylinder misfire.
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Tuesday, April 20th, 2021 AT 4:47 PM
Tiny
NICKOLAOSF
  • MECHANIC
  • 69 POSTS
Multiple coils on one (what cylinders)and did you swap them?
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Tuesday, April 20th, 2021 AT 9:41 PM
Tiny
JEFF HERMAN
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  • 444 POSTS
It started snowing, LOL. You want me to swap one three and five with two four and six?
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Tuesday, April 20th, 2021 AT 9:43 PM
Tiny
NICKOLAOSF
  • MECHANIC
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Yes and clear codes and retest to see if codes have changed.
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Tuesday, April 20th, 2021 AT 9:52 PM
Tiny
JEFF HERMAN
  • MEMBER
  • 444 POSTS
I swapped the coils side to side and got the same code random multiple cylinder misfire po300. It occurred to me that I was causing some codes when I was pulling the coils off and testing for dropping RPM. I drove this vehicle barely 10 miles closer to where I could work on it easier and it had trouble getting over 2,000 RPMs, it had trouble shifting unless I let off the gas, and obviously it had no power. Read the codes when I got home po300, PO700, po562. I think I have to get it running on all six before I can worry about the transmission issue. I also noticed that the coil on cylinder one jumped off because I did not have them bolted down for this short trip so that may have been causing less power. Finally did something I should have done in the first place and check the oil to see if there was coolant in there and there's not and there's no oil in the coolant so I'm assuming the head gasket is okay. Also my preliminary compression check of 150 on cylinders one and cylinders two indicates that Cam's are working and head gasket is okay. So what's next? I'm trying to get a hold of a COP tester to check the coils while it's running for secondary coil issues.
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Wednesday, April 21st, 2021 AT 12:13 PM

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