Misfire / rough idle

[Huskey411]

2004 Tj
4.0 5spd
Hello, I changed my spark plugs yesterday and did a transmission fluid change. After about a days worth of driving, the Jeep started running rough, and then has a violent vibration when the engine is underload. The check engine light also came on for P0301. I checked all the plugs and they all worked okay. I'm not entirely sure what to do next

 

[Jerry Bransford]

The coil rail spark plug boots are correctly and fully seated down over each spark plug? It's not hard to miss a plug when seating the boots, I've done it.

 

[KingCarGuyZ]

If there seated there’s a procedure to test the coil pack with a ohm meter. I’d do that next

 

[Huskey411]

The coil rail spark plug boots are correctly and fully seated down over each spark plug? It's not hard to miss a plug when seating the boots, I've done it.

I've made sure its seated correctly, by applying pressure on all of the plugs before I tighten the coil rail. It had the same result unfortunately.

 

[Huskey411]

If there seated there’s a procedure to test the coil pack with a ohm meter. I’d do that next

Can you post a link to this procedure? I will try that next

 

[Daryl]

 

[KingCarGuyZ]

I think it was something like check 1&6 2&5 and 3&4, at the spark boot. should be resistant between them, If not it’s dead. Can’t find the exact procedure rn.

 

[Huskey411]

I think it was something like check 1&6 2&5 and 3&4, at the spark boot. should be resistant between them, If not it’s dead. Can’t find the exact procedure rn.

The coil rail is okay. I went through and checked all of the resistances and all of the coil packs to make sure they were all getting spark and they all were. Any other ideas?

 

[KingCarGuyZ]

The coil rail is okay. I went through and checked all of the resistances and all of the coil packs to make sure they were all getting spark and they all were. Any other ideas?

If the rail is sparking and your getting a nice blue spark, maybe spark plug gap, or you have a fuel problem.

 

[Steel City 06]

You got a P0301 code, which indicates the misfire is cylinder 1.

Swap that plug with another one and see if the misfire follows

 

[Huskey411]

If the rail is sparking and your getting a nice blue spark, maybe spark plug gap, or you have a fuel problem.

I'm thinking I might have a bad injector, I've unplugged them one at a time with the engine running, and cylinder one has no effect on the engine. While moving other ones makes the engine run significantly worse.

 

[Huskey411]

You got a P0301 code, which indicates the misfire is cylinder 1.

Swap that plug with another one and see if the misfire follows

Yes I went through and checked the coils and all of the plugs. So they are all good. I'm trying to figure out what else it could be

 

[Wayne Mathson]

Yes I went through and checked the coils and all of the plugs. So they are all good. I'm trying to figure out what else it could be

I was experiencing the same issues with my ‘04 LJ 4.0 this past summer. Read on this forum about K Suspension’ s coil mod and checked it out. Decided to make the investment and now very happy that I did. Engine runs smooth and very responsive. My issue then was the the coil rail. Had changed plugs but was still getting intermittent error codes. Easy to install.

 

[KingCarGuyZ]

I'm thinking I might have a bad injector, I've unplugged them one at a time with the engine running, and cylinder one has no effect on the engine. While moving other ones makes the engine run significantly worse.

If unplugging cylinder 1 has no effect on the engine, and all the others cause it to stumble, then yeah id say you have a bad injector, might just be the injector O-ring to.

 

[Huskey411]

If unplugging cylinder 1 has no effect on the engine, and all the others cause it to stumble, then yeah id say you have a bad injector, might just be the injector O-ring to.

I think my next step is going to be to pull the fuel rail and test all of the injectors see if they are all working.

 

[Huskey411]

I was experiencing the same issues with my ‘04 LJ 4.0 this past summer. Read on this forum about K Suspension’ s coil mod and checked it out. Decided to make the investment and now very happy that I did. Engine runs smooth and very responsive. My issue then was the the coil rail. Had changed plugs but was still getting intermittent error codes. Easy to install.

I just looked into it, seems like a very convenient upgrade to make life way easier. I am not sure that would help me though because I don't think my problem is the coil pack. I think it is my fuel system. Thanks anyway for the input.

 

[cpwolf]

I was experiencing the same issues with my ‘04 LJ 4.0 this past summer. Read on this forum about K Suspension’ s coil mod and checked it out. Decided to make the investment and now very happy that I did. Engine runs smooth and very responsive. My issue then was the the coil rail. Had changed plugs but was still getting intermittent error codes. Easy to install.

What mod is this? K suspension, I'm not seeing that.

 

[Huskey411]

If unplugging cylinder 1 has no effect on the engine, and all the others cause it to stumble, then yeah id say you have a bad injector, might just be the injector O-ring to.

I went through and checked all of the injectors, and they all squirted fuel fine. I used the correct plugs and a water bottle and cranked the engine over and they all squirted fuel. The spark plugs worked, and the coil packs work. So now I have absolutely no clue what it could be.

 

[KingCarGuyZ]

I went through and checked all of the injectors, and they all squirted fuel fine. I used the correct plugs and a water bottle and cranked the engine over and they all squirted fuel. The spark plugs worked, and the coil packs work. So now I have absolutely no clue what it could be.

Did you inspect/replace the injector O-rings? Could be providing a junk seal and leaning it out

could be just really bad gas, when/where was the last time you filled up? These things will run on mud, but they don’t like it.

your confident in your fuel, we’ve gone through spark. Compression/timing? If it’s running I’d expect your compression to be “good enough” maybe your out of time with the cam or the crank sensor is out of time with the actual crank?

how does it run off of idle? Like if you hold it at 1500? Smooth out then?

edit: at this point I’m just throwing ideas around.

 

[Huskey411]

Did you inspect/replace the injector O-rings? Could be providing a junk seal and leaning it out

could be just really bad gas, when/where was the last time you filled up? These things will run on mud, but they don’t like it.

your confident in your fuel, we’ve gone through spark. Compression/timing? If it’s running I’d expect your compression to be “good enough” maybe your out of time with the cam or the crank sensor is out of time with the actual crank?

how does it run off of idle? Like if you hold it at 1500? Smooth out then?

edit: at this point I’m just throwing ideas around.

Yeah anything helps honestly. I am going get a compression tester, and test the compression. It seems to rev okay... but if the engine is trying to rev under load the entire vehicle violently shakes. I had just put gas in it 9/20/20 so it has fresh gas. I might try getting new cam and crank sensors see if that helps. I have seen on some other post that it could be part of the valve-train, so I am also going to try to take the head cover off and check all of my valves because maybe one of them is being held open or something, not really sure.

I don't know if i mentioned this earlier, but there is a puffing noise coming out from the exhaust that doesn't sound normal. It might just be a symptom of a misfire, or maybe not. Figured id throw that in.

Edit: Do you think there is any chance there is a ground problem between the spark plug and the block?