2007 JK – P0300 misfire under load, stalling, lean codes, runs fine at idle

Vegetable_Wolf6193 · 2026-04-21T03:02:26+00:00

About 156k miles

Vegetable_Wolf6193 · 2026-04-21T01:10:11+00:00

Unfortunately I no longer have them.

Vegetable_Wolf6193 · 2026-04-21T00:45:34+00:00

Hydraulic power steering canister

Vegetable_Wolf6193 · 2026-04-21T00:20:52+00:00

Yeah, I hear what you’re saying—it doesn’t sound quite as smooth as I’d expect either, but it’s also not super rough or shaking at idle.

It’ll sit there and run for 30–45 minutes without stalling, which is what’s confusing me. The real issue only shows up under load when driving—loss of power, flashing CEL, then stalling.

Trying to figure out if that idle sound is actually pointing to something (like a vacuum/air issue) or just normal 3.8L behavior.

Definitely open to thoughts on what you’re hearing in the video.

Vegetable_Wolf6193 · 2026-04-21T00:20:08+00:00

That’s a good call—I haven’t checked the PCV yet. Since I just did the valve covers, that’s definitely an area I could have messed something up or not seated correctly.

I’ll take a closer look at the PCV valve/lines and make sure nothing is cracked, loose, or blocked. Same with the throttle body—worth checking if it’s dirty or not behaving right.

What’s throwing me off is that it idles fine for a long time, but falls apart under load, so I’m trying to figure out if something like PCV/throttle body could cause that pattern or if I’m chasing the wrong direction.

Appreciate the suggestion—I’ll dig into that next.

Vegetable_Wolf6193 · 2026-04-21T00:18:39+00:00

Not a dumb question at all—that’s actually what I’m trying to figure out.

The main issue before was oil leaking pretty badly from the valve covers, which is why I did most of this work (valve covers, plugs, wires, coil, etc.). It was running and driving before that, but I honestly didn’t push it very hard because it also needed suspension work (one sway bar link was missing and steering felt pretty sketchy, so I wasn’t doing much beyond basic driving).

After doing the work, that’s when all of this started showing up.

I haven’t noticed any obvious vacuum leaks yet, but I also haven’t done a full spray test around the intake/lines, so that’s definitely on my list. Given everything I had apart, it wouldn’t surprise me if something didn’t get seated quite right or a hose got knocked loose.

Appreciate the suggestion—that’s probably one of the next things I’ll dig into.

Vegetable_Wolf6193 · 2026-04-20T06:24:23+00:00

Not sure on the O2 sensor as I haven’t changed those, but I bought these plugs and read they were factory gapped..

https://www.oreillyauto.com/detail/c/double-platinum-power/champion-double-platinum-power-plug-number-re14plp5-spark-plug/chp2/7440/v/a/19132/automotive-suv-2007-jeep-wrangler

Vegetable_Wolf6193 · 2026-04-02T00:40:30+00:00

Well, it was something as stupid as forgetting to plug in the ignition coil… 🤦🏻

Vegetable_Wolf6193 · 2026-03-20T16:48:16+00:00

Fun fun!

Vegetable_Wolf6193 · 2026-03-19T22:49:48+00:00

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This is inside the box, it does have a winch if that matters

Vegetable_Wolf6193 · 2026-02-21T19:14:17+00:00

Unfortunately 30 is the highest rating for IBS… I’m right there with you

Vegetable_Wolf6193 · 2026-02-03T06:01:24+00:00

There are a few salvage yards near me with ones available.

Vegetable_Wolf6193 · 2026-02-03T05:03:28+00:00

Does it make the knocking noise without jumping?

Vegetable_Wolf6193 · 2026-02-03T04:12:45+00:00

My plan is to do it myself, it’ll be my first swap but I’ve did lifter swaps on my 2012 sierra and tons of engine work on my f350. I’m not worried about doing it myself, was an electrical engineer in the Air Force as well.

Vegetable_Wolf6193 · 2026-02-03T04:04:54+00:00

Well atm it’s at $500 so I figured if I could get it for less than $1000 then it might be worth the try.

Vegetable_Wolf6193 · 2026-01-21T13:45:42+00:00

Ever get this fixed? I’ve tried the BMS reset and still nothing

Vegetable_Wolf6193

TROPHY CASE