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2012 Chrysler Town and Country - Loud knocking then dead after spark plugs replaced

I generally do most of my own maintenance or at least give it a shot. In this case I must have done something really wrong. Please assist.

I have a 2012 t&c with the 3.6 pentastar flex fuel engine. It started running rough and was throwing a code. Took it to auto zone and had them test code and they said it was p0301. Possible bad plugs, coil, etc. bought new plugs since I have 156k on originals. Replaced all 6.

Drove the next day, seemed fine. After about 100 miles, displayed same stuttering at 70mph, slowed, did it for another couple minutes then stopped. Figured there was still a problem.

Bought a new coil/boot and replaced #1. While doing so, I took off the manifold again (I know NOW I didn’t really have to do that to get to #1) and realized bolt 1 was broke. Also broke the tab that hold the harness firm to the boot. Harness still stays on fine, but worth mentioning.

Put the manifold anyway and tightened them all too tight. Didn’t realize 8nm was soo not tight. Now I do and have a torque wrench. When I started it (accidentally did it without the sensor that goes back into the port on the air intake. Not a big deal but more detail the better), barely started and was ticking/knocking super loud. Turned it off and replaced the boot/coil with old one. Same problem. Oh yeah, also put a whole can of sea foam in with a 1/4 tank of gas.

Took off manifold and tried to get broken bolt out of the bottom part of plastic manifold with an extractor but only was able to push it further down. Bought all new bolts from Chrysler and put them all back in torqued to 8nm. Cranked, sounds terrible. Added another 1/4 tank of gas to dilute the sea foam and ran again. Sounded a tad better but after a minute it sounded like something clinking around in engine then died. Can’t restart.

What am I missing? Was thinking now I have to take off manifold, upper and lower (wrong term maybe?) and take off heads to see what may be there. Could the end of that bolt have made its way into engine?? That is my fear.

Thanks for your input. Sorry for all the typing. More info the better.

Double check that none of the spark plugs are loose. Sometimes a diyer will forget to tighten one of them and it’ll start to unscrew and that will make a lot of racket, and can damage the threads if it goes on long enough. You might just want to remove them all and reinstall. When you do that you can also peer into the hole , or use a magnetic pick up gadget, to see if you see or latch on to anything inside the cylinder. I doubt something inside the cylinder is the problem though.

As I recall that particular engine has had some problems w/valve springs. A broken valve spring could cause these symptoms.

Thanks, will try that tomorrow. The strange thing to me is that it was running (had check engine light and was a bit rough but running) before replacing boot/coil and breaking bolt and adding sea foam, but now won’t even run. Will check all plugs though.

Whenever I remove spark plugs I vacuum the area around the spark plug first. I have to make a special attachment to the shop- vacuum to do it out of a piece of card stock.

You do not need to remove the head to diagnose this. It can be done by a mechanic. Although I appreciate your willingness to tackle repairs, I think you may have gone beyond your training. It may be time to turn to a professional

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I am right at the edge of going to a mechanic. I just thought I would throw it out to the community first. I fixed a lot of stuff Over the last few weeks because I really just want to sell the van. I don’t really need it. But I want to sell something that works, not a problem.

Check the firing order just in case you got the wrong wire to the wrong plug. I do plugs one at a time, stuff happens.

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Thanks for the input. I took out the spark plugs one at a time and only replaced one of the boots. none of the wiring was messed with and is still in the original location and zip tied accordingly. It is impossible for them to be mis-wired the way it is.

Are you absolutely sure you didn’t drop a manifold bolt… or a piece of one into the engine?

One of the manifold bolts broke in half. The other half, I cannot locate, so technically, maybe it could have? However, I only took the top part of the air intake off. The bottom part (the other part of the plastic housing the bolts screw into) is still there. When I tried to use the bolt extractor to get the other part of the bolt out, I think it just screwed it in more? I will have to take that part of the housing off to see how it is set up underneath. It may be possible that there is no physical way to get to the engine from that part of the housing. But I will not know until I take it off or google someone who already has.

It seems pretty unlikely the broken part of the manifold bolt left in the hole when the bolt’s head snapped off could make its way into the engine. If you poke some sort of probe (piece of wire, etc) down that hole I expect you’ll find it’s not a through hole; i.e. the lower part of that bolt is still inside the hole. But it is possible of course something else fell into the engine during all this.

Are you able to turn the engine by hand, using a socket on the crankshaft pulley bolt?

So, it turns out that when I put the manifold back on at one point, and tried to tighten down one of the bolts (number 1), it was askew and it broke in the tightening. The piece that broke off went down into the valve area and sure enough. blew the engine. I just sold the van to someone who will replace the engine. Lesson learned I guess and a couple thousand dollar mistake.

OMG… That is something that you must absolutely NOT do when changing plugs. I am sorry to hear that you did this. The engine itself is not “destroyed” it just has valve damage and also possibly cylinder and piston damage. Its repairable but not many people would tackle this repair…they would just replace the engine as they are relatively “cheap” meaning they can be obtained for $1000 or less… then its just the installation price…

This is really a terrible thing to have happen…I wont go into all the precautions you should have taken in order to NOT drop anything down into the spark plug hole. Again…sorry to hear of your dilemma. Ugh…