Replaced spark plugs and leads, engine runs lumpy

[acs85]

I changed the JKU's OEM spark plugs with a set of NGK LZTR5A-13, and in the process broke an ignition lead so replaced them with a set of Eagle ignition leads (recommended through the JWORA Facebook group).

Started her up no problem but the engine is running a little lumpy and the exhaust smells like fuel. I pulled out each spark plug and they look like they've been sparking, they've lost their shine, so I reseated them and torque'd them to spec. Double-checked the leads were plugged on to the correct spark plug, too. Started her up again but no change.

I noticed that spark plugs 1, 3, 5 looked like they had some black carbon on them already, but 2, 4, 6 were quite clean. Spark plug 3 had a tiny bit of oil on it, not sure if I should be concerned about that.

Other than testing the OEM spark plugs, not sure what else to check and would appreciate any ideas.

[acs85]

Well, this morning I swapped (one at a time) new for old spark plugs and found that although new spark plug #2 is sparking, the misfiring/lumpiness doesn't occur when the old spark plug is in. Reckon I'll need to replace the new spark plug with a new new spark plug.

[Banshee]

When I had that problem, I was getting the 'mutilple random misfire' code as well.

Turned out that, despite checking everything 3 times, I still managed to swap 2 leads over on the right side...

I learned that the 3.8 V6, while it will run, does not run well on 4 cylinders.

[Das_Colonel]

Had my old V8 go into 'limp home mode' once, running on 4 cylinders due to a ECU fault. It was very uncomfortable to drive.

[st_za]

Check the gap on your new plugs - I have had a few from NGK that must have slipped through their quality control.

[Nanook]

Aaron,

Can you please give me the part numbers for the Eagle leads?

I'm going to change mine soon and it would save me some research.

Thanks

[acs85]

Ok another update: I got a new NGK spark plug and it solved the problem. I'm not sure what was wrong with the first plug, visually it looks fine and the gap is the same as the others. Maybe a QC issue like @st_za had.


I could've saved myself bit of time if I had an OBD reader! Reckon I'll get one off ebay later today.


@Nanook, sure mate, here's a pic of the box: