2004 Marauder, approx 180K, well maintained. She uses some oil, but not terrible.
I have been battling this for a while in my spare time which is slim. I’ve had my mechanic friend with the uber expensive Snap-On computer look when it’s been happening too. Car could be great for a few weeks then occasionally and randomly I’ll get a P0300 (Random Misfire) along with some stumbling on acceleration and idle. Sometimes this is combined with other codes. Sometimes not. SOMETIMES when it’s misfiring I have no AC.
My diagnostic ability is limited because it will usually "fix" itself before I get back home and I can't find the problem if it's running great in my driveway.
At random, my symptoms are, and in various combinations:
Fortunately I've never stalled out or been stranded because she always comes back like a Phoenix.
- Drive great, misfire a little, get worse, then smooth out and be fine
- Instant light on startup and drive like poop, or light on startup and drive like eh, but drivable
- Driving fine for a while and suddenly misfire with light immediately
- Driving fine for a while and a light and misfire many miles later or no misfire at all
- Driving fine, misfire, park it, shut off, start up, and it’s all better…or not
- Misfire, AC will blow hot for a while, magically come back
Over the last few months some codes that I recall have been:
….Replaced crank position sensor, then later got…
- P0352 – Ignition Coil B primary/secondary circuit
- P0356 - Ignition Coil F primary/secondary circuit
- P0305 – Cylinder 5 misfire detected
- P0316 – Continuous misfire detected on startup first 1000 revolutions (Showed up a few times over a few days but not before)
This past weekend when I was replacing the coils and adding Granatelli connectors, I noticed a little oil in #6 hole so I did the cover gasket. In retrospect I realize I didn’t pull the plugs. Oops! But after I did the coils, it has some issues finding a good idle, but eventually settled down. Took it for a spin and drove AMAZING like it got a shot of adrenaline and I loudly whooped “She’s BACK!” Drove it for a couple days and all good. Big smiles. Happy dance. Then this morning, 5 min down the road, light, misfire, flipped it around and drove the Jeep to work with my head down in shame.
- P0315 – Crankshaft position system variation not learned (This one has not come back since shortly after the new CPS)
So to recap, replaced plugs, factory coils, few COP connectors had exposed/green wires so soldered and replaced and replaced cam cover gasket on PS, new PCV and hose. (The PCV to cam cover detents where the PCV turns and locks into the ‘grommet’ are a little worn so the PCV is possibly cocked a tad. Can’t find replacement ‘grommet’ part that bolts into the cam cover). Cleaned MAF & air filter. Did injectors a while ago when this first started. Techron a couple times in the past. With my mechanic's Snap-On, he's actuated/tested all the stuff he can like EGR, etc.
As my last act, I’m going to pull the plugs this weekend, again, and put in a new set of XP104’s. That way I can be 100% sure it’s not the COP/plug. Again. Kind of.
I haven’t ruled out things like the PCM or an intermittently broken wire somewhere and if this were persistent it’d be a different story, but it’s RANDOM, and goes away on its own. And coupled with the AC issue, I just don’t know. I've been playing with my various 4.6L's for something like 18 years so I know my way around the platform. This has me stumped. After years of fiddling with a seriously annoying problem, I’m about ready to call it quits. I trust my Jeep and Suburban more and I know FAR less about those vehicles.
Thoughts?