2011 Jeep Grand Cherokee with 3.6 random misfire codes

[DonFitzwater]

My daughter's 2011 JGC is showing a little misfire at low speeds. My scanner is showing a random misfire P0300 and P0306. I ran it thru town with the cylinder data showing and #3 and #6 were misfiring. I'm going to pull it in the garage tonight and do a leakdown and compression test and if those are good, throw a set of coils and plugs at it. Unfortunately I found a TSB from 2011 describing a check engine light caused by head problems.......I hope thats not the case. Jeep has 124k on the clock.

Any of you guys have any experience with the 3.6? I don't have any currently.

 

[TFucili]

We just got ours, so no help there. Motor City Mechanic has had quite a few Pentastar videos, and he will generally answer emails too.

 

[Ozymandias]

How old are the plugs?

 

[AEdelheit]

On our 2012 we had got an email the FCA extended the warranty coverage on the cylinder heads to 150k miles / 10year I believe, might be of on the exact figures but there is a good chance it may still be covered as it was such a large issue.

 

[DonFitzwater]

How old are the plugs?

No idea. Will be getting into it first thing in the morning. More monitoring showed misfires one 1, 2, 3 and 6. Will leakdown and compression it then throw in a new set of coils and plugs...will post pics if I find anything interesting.

 

[TFucili]

You may end up taking a peek at the cams/followers.

 

[DonFitzwater]

You may end up taking a peek at the cams/followers.

We’ll see how she does when I leakdown it...it’s whisper quiet when running, no ticking.

 

[TFucili]

I know with OHC, VVT, etc. the 3.6 Pentastar is a whole different animal than the old 3.5 that was in my wife's '06Charger, but that used to regularly throw a multiple cylinder misfire code. It had the two stage intake, and if a bit of carbon got on the mating surface of the flapper door it would throw the code. The fix was to remove the actuator motor, turn the shaft a bit with a screwdriver, and let it slap shut a few times, knocking the deposits away. Clear codes, and all would be well for a while. I don't imagine any of that applies here. I'm going to have to get up to speed on this engine.

 

[DonFitzwater]

This little motor “appears” to be very simple in comparison. Tomorrow should shed some light!

 

[mwilson]

On our 2012 we had got an email the FCA extended the warranty coverage on the cylinder heads to 150k miles / 10year I believe, might be of on the exact figures but there is a good chance it may still be covered as it was such a large issue.

^^^^This^^^^

I remember this happening, and there may well be coverage on it....just in case it is the heads....

 

[Ozymandias]

I bet on the plugs, the change interval is way to far stretched from the factory.
Had the same experience with my HEMI when i bought it used with like 50K miles, plugs worn but interval is 100K miles.

 

[DonFitzwater]

Near zero leakdown. Plugs were pretty bad.

 

[DonFitzwater]

Fairly certain they were original. Wrapping up the plug and coil install now.

 

[mwilson]

It certainly looks like they might have been the problem.

Beats the alternative for sure!!

 

[DonFitzwater]

What a wonderful little engine. This thing is simple and after the new plugs and coils she's smoooooth with no misfires while warming up. I'm headed to town for an extended drive.

 

[DavidC]

As bad as those plugs looked I am sure you did the fix. Wish the Wife's Toy was that easy. To get to the rear plugs on that stupid sideways engine yo have to disassemble the top of the engine and that"s after you remove the wipers, cowl panel and wiper motor. What a PIA.

 

[gsbrockman]

Near zero leakdown. Plugs were pretty bad.

So....OE plugs still in it I presume?

 

[TFucili]

That's good news, Don!

 

[Ozymandias]

Win

 

[DonFitzwater]

Yes, plugs were the originals. 124k miles. I installed new coils and new Champion plugs (factory gapped but I checked them). Instantaneous improvement in idle quality and after a 40 mile test drive I can say it’s fixed. It is a smooth engine and all cylinders are firing normally with no more misfires.