P0304 Cylinder 4 - misfire detected

[kill_dano]

https://imgur.com/a/O3LJabl

2000 TJ 6-cyl / 4ltr / manual
Having a Cylinder 4 misfire. Does the noise from the video point to anything in particular? Sounds kinda metallic. Does it rule anything out?

I had a misfire issue a couple of years ago, and I replaced the spark plugs, fuel injectors [I've since reinstalled the original fuel injectors], and finally, the coil pack fixed the issue.

 

[Chris]

Hard to tell for sure but it sounds like it's misfiring and potentially has an exhaust leak. Can you feel around while it's running and make sure there's no noticeable exhaust leak?

Assuming that's not it, you've got a really bad misfire and you need to pull the codes on it to see what they say.

Did this happen after you did the engine work or was it doing this even before and these are the parts you've thrown at it?

 

[JKP]

Codes?

Pull the plug and examine. Swap with another plug.

Remove oil cap, cyl 4 is right behind it, see if noise is louder. Possible rocker arm/spring issue?

Also, check for coolant on the head between 3 and 4. If the head is original, they are known to crack there.

Bad injector? Measure the injector resistance and compare to the others. All should be within a few ohms of each other. Can also swap with another injector.

 

[swtrailboss]

The noise could be a manifold leaking. Check the bolts(studs) specifically back by cyl #4 to see if any are missing……this isn’t going to fix the misfiring but as JKP said plug, valve spring , head gasket or injector. Check all the above.

 

[kill_dano]

Assuming that's not it, you've got a really bad misfire and you need to pull the codes on it to see what they say.

The only code is pending:

P0304 Cylinder 4 - misfire detected​

Also it does pop a large evap leak code if I don't reset the ECU for a couple weeks, but I've been unable to figure out the source of the leak.

Did this happen after you did the engine work or was it doing this even before and these are the parts you've thrown at it?

The work from 2 years ago was only because of a misfire code and loss of some power. The parts I threw at it were for this issue from 2 years ago.

I reinstalled the old fuel injectors like a year ago cause of a code that made me think one of them was leaking or something, and the old ones fixed that issue.

I've been feeling for a while now that the engine doesn't sound healthy, and it has what sounds to me like an air vacuum suck sound from certain angles, but I've never been able to figure out where it was coming from... but this all didn't cause me any codes or issues, so I let the noise go.

This new thing is I noticed the engine sound was much louder and unhealthy sounding... noticed a loss of power, so I checked the codes and saw the misfire one.

I've connected a smoke machine to the tail pipe don't see smoke coming from exhaust manifold. I've also poked around while the car is on and don't notice any leaks.


Today I got one of those stethoscopes, and checked where the noise is louder:

oil cap/Head case sounds medium loud
oil pan: Sounds slightly lower than medium loud.
Touching any part of the exhast sounds high loud.

Not sure if that matters.

Also the loud rhythmic clicking sound goes away after the car has been running for a while.

What I'm going to do is disconnect part of the exhast that connects to the Cat and muffler, and then send smoke up from there to the engine, cause maybe that will be able to make enough pressure to show a leak.

 

[JKP]

Collapsed/sticking lifter.

Start the engine, let it run for 10 to 20 secs. Shut it off and let it sit for a couple of mins.

If no noise when you restart, the lifter has pumped up.

If this is the case, run some HM oil, or maybe the new Valvoline Restore and Protect, or the new M1 Clean.

 

[kill_dano]

I connected the smoke machine to Y pipe that goes into the exhaust manifold and found two smoke leaks. Still can't see any leaks further up in the manifold. I'm going to repair the leaks with my welder, and I'll report back.

 

[Intimnasc]

For me it was cylinder number 5. Do a compression test, leak down test, check plugs and wiring. If all else fails take the valve cover off and put an indicator on each rocker and measure how much lift each one has while someone rotates the motor from the harmonic balancer. Mine the number 5 exhaust was not opening all the way. Turns out I had a flat lobe on the cam and a ground up lifter.

To me it sounds like (and I am not the best gear head) a lifter tapping or a rocker tapping.

 

[Chris]

I connected the smoke machine to Y pipe that goes into the exhaust manifold and found two smoke leaks. Still can't see any leaks further up in the manifold. I'm going to repair the leaks with my welder, and I'll report back. View attachment 664355

Cool, let us know what you find and if that resolves the issue. Sure sounded like an exhaust leak to me.

 

[Jakes-2004-TJ]

https://imgur.com/a/O3LJabl

2000 TJ 6-cyl / 4ltr / manual
Having a Cylinder 4 misfire. Does the noise from the video point to anything in particular? Sounds kinda metallic. Does it rule anything out?

I had a misfire issue a couple of years ago, and I replaced the spark plugs, fuel injectors [I've since reinstalled the original fuel injectors], and finally, the coil pack fixed the issue.

I have a 2004 TJ (6CYL) that had intermittent misfires, I installed new spark plugs (Autolite 2986 Copper type) only to have random misfires continue. I swapped plugs between cylinders and noted the misfire followed this one particular Autolite spark plug. This week I installed a new coil rail from NAPA (made in Poland) [not an Autozone Made in China rail] and new Bosch 6717 (Platinum type) spark plugs. The Bosch plugs come pre-gapped at 0.040 and I verified each one. I dos-connected the battery while installing the plugs & rail to get the computer to reset. Did a test drive and no misfires or CEL so the Bosch plugs & new rail seemed to have resolved the problem.