Mechanic is stumped


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I have a 2011 JGC Overland V6, 160k miles. Replaced Cat Conv in Sept, then noticed engine running rough. Eventually CEL came on. Mech said cylinder misfire 2, but the oil cooler was bad and needed to be replaced. Done.
One week later, CEL came back and now read Cylinder misfire for 2-4-6. Replaced all 6 plugs and three coils (2-4-6). Mechanic said all good.
CEL came back next day and then I noticed oil drops in my garage within 3 days. Next day, he pulled apart everything in front of me to confirm it wasn't the Oil Cooler and did compression check - all good on compression. However, Spark Plug for Cylinder 2 (one week old) was burnt. He kept looking and suggested PCV Valve which had oil in it and then when up on the rack noticed a lot of "oil" at the seal for engine and transmission. Replaced the PCV (important note: he spent 6 hours on it and only charged me for the PCV valve - solid dude). Within 5 miles of driving away, CEL came on.
I'm already 2G's into this guy (1200 for tune-up and oil cooler, 800 for cat) and I'm concerned he may not be capable... Thoughts?

Was everything good until the cat was changed, as in you drove it for years, or is this Jeep new to you?

I don't have any good advice at this point. You may call another shop and ask if they can diagnose for $100 or so.

First why was the CAT replaced?
What we're all the codes you had recently. What was done and what was replaced?

Cylinder 2 misfire caused by oil cooler does not add up. Was there oil in the coolant or coolant in the oil?
Go check.
When cold open the radiator cap and see if there is oil floating on top.
Also pull your oil dip stick and see if it is coated in chocolate shake.
How did the old plugs look before he changed them? Any coated in oil or burnt?
The rubber plug near trans.? Did he mean rear main seal? This can leak. Ut not normally from no leak to dripping a lot. You would have notice this... Do you change your own oil? Or crawl under once in a while to check things out?

Oil in the PCV can be caused by excessive blow by or bad PCV. This leads to oil in intake and filter area.

Post pic of burnt cyl 2 plug.


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First, thank you for replying. I am not a "car guy" so will do my best to not embarrass myself in my answers.

The cat was throwing codes for a few months. Was told it wasn't a big deal so just waited until inspection was due to fix it. he replaced the drivers side in October - pass side was replaced a few years ago. I don't have all the codes anymore (wasn't saving them) but numerous trips to Autozone was the same thing everytime re: the cat.

a week or two after the cat was done, CEL came on - said Cyl2 misfire and really stated noticing rough idle. Talked to mech, he said not urgent, get scheduled and we'll do a tuneup. A few days later I heard a "sloshing" sound from the engine when I turned it on and then it started running "warm", not hot - just elevated temps. Got home and checked, coolant resevoir was bone dry. Then started noticing "drops" of somthing on the garage floor. Took it in and thats' when he said Oil Cooler. At that time, Cyl's 2-4-6 were all misfiring. Nov 8 he replaced oil cooler, all 6 plugs (Champion) and the coils for Cyl's 2-4-6.

Didn't check dipstick before he did all this, so I don't know about that part.
Didn't see the plugs before he replaced them Nov 8, however, he did show my the NEW plug for Cyl 2 last week and it was burnt pretty good. And I don't have that one to post a pic.

The plugs near trans must be rear main seal. There are two of them side-by-side. I didn't have any leaking at all before the oil cooler situation. Crawled under yesterday and can see it is still leaking with spray down the undercarriage. Without getting it lifted, I can't tell exactly where it's coming from.

SPoke to mech yesterday and he asked me to leave it with him for the entire day so he can search for the leak.
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I know i replied to this at breakfast. Where did my post go?

Anyway the sloshing snd dry expansion tank makes me think you may have overheated it and either cracked a head or the head gasket. 246 are all on one side of the engine any chance the intake and exhaust is loose or leaking?

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If you have a cracked head or blown head gasket , would not the coolent get mixed with the oil turning it into the color of coffee with milk added to it .