Merry Christmas Scotty. I'm working on a 2014 town and country 3.6l with just under 100k. The front head was off 4 times and sent to 2 different machine shops to have valves and seats resurfaced and valve length corrected for a misfire. The misfire started on cyl 6 then cyl 4 twice and back to cyl 6. When misfiring, there is a suction at the tail pipe and a puffing sound from the intake. Replacing lifters, switching plugs, coils, and injectors doesn't change anything. Scan tool shows no misfires, no C.E.L. and no codes, but it's obviously misfiring. I'm out of ideas.
What you tell me is that with the abnormal noises from the tail pipe..the valves are not closing thats why you near noises. as for no CEL light..you should put that to the test by disconnecting one of the Coils and see if it can detect a missfire. If it can't your ECM is defective in some way. if it does thats a good thing. But you should take a compression test to see if the miss fire cyl is as good as the others next to it. Its just a test to validate what the compression compared to others. If its the valves not closing then it should be lower than the others. Also the scan tool setting on the MISSFIRE menu shows no miss fires also?
I unplugged a coil and the scan tool still showed no misfires, but I saw this happen on a couple of other cars over the past few years. The compression reading on the bad cylinder can get just as high as the other cylinders, but i had to crank the engine longer for the bad cylinder because the valves didn't seat everytime.
maybe I should clarify...the scan tool did not detect a disconnected COP while the car was runnng? I have never run into that scenario. I mean..thats the very situation the ECM is suppose to detect because the crank sensor detects abnormal RPM cycles of Fast and Slow down which is how any missfire is detected. But getting back..if the valves are not seating it is kinda futile to continue..You have to pull the head and mount the cams to see WHY they don't seat...if the valves don't seat...nothing in the ECM is going to help you. as its a mechanical problem. Now does this engine have any kind of variable valve timing controls ? I think you have to focus on the head problem and why the valves are not closing...Yea..I don't envy you...its a pain...
I know its definitely a head problem and I will focus on that. The valves on the bad cylinder close everytime i turn the engine by hand, but cranking the engine for a compression test the valves sometimes don't seat. The valves almost never seat when the engine is idling, but the car runs fine at higher rpms. Yes the engine has variable valve timing. I won't worry about the ECM, it's just strange that I can disconnect a COP and not detect a misfire or a disconnected COP on the scan tool.
Is it possible there is something wrong with the VVT but its only on one cylinder tho. I dunno...concentrate on the valve situation and I think the other errors will go away...other than the NO CODE when the COP is not hooked up...I would have to look at another same vehicle and do the same to see it does the same!
Typical chrysler product lol😉
Have you done a cylinder leak down test to confirm this? It is a very simple test and it will tell you if its an intake or exhaust valve not sealing. Although if it's intermittent you might have to try it several times.
Also when the heads were off did they replace the guides? If the valve guides are worn out it could cause the valves to "wobble" around and not seat square every time. On the other hand if they guides are damaged "mushroomed" or the tolerances are too tight it could cause the valves to bind up and not fully close every time.
Problems like this can be very frustrating. I hope you get to the bottom of it
