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MISFIRE = "to have the explosive or propulsive charge fail to ignite at the proper time <the engine misfired>"

Valve train can be the cause by failing to provide the proper fuel:air mixture at the time of ignition (as in failing to purge all/enough of exhaust gasses or not allowing fresh mixture to fill the cylinder) or failing to hold pressure generated by the explosion..
I suppose that makes sense, which explains why a worn camshaft cause a miss-fire. However has it worn out that much?
 

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I suppose that makes sense, which explains why a worn camshaft cause a miss-fire. However has it worn out that much?
First, worn cam lobe is speculation at this point (and will be until confirmed).
How worn does it have to be to cause a misfire - not that much, 1/32" would probably be more than enough.

If it is the cam lobe, it will get progressively worse over time..
 

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Discussion Starter #43
@04anniversaryedition

Yes, since December I have added probably 10 cans of seafoam and Chevron cleaner.
 

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Discussion Starter #44
@atoman

It initially passed a compression test. At the dealership, it failed and that's part of the reason they decided it was a worn cam lobe. I don't understand how a roller cam can get a flat lobe. I think it's something in the valve train on #1. I have a hard time believing it's a roller cam. I think it must be the lifter, spring, or valve. What's frustrating is that my mechanic had the engine apart and looked at all of that and tested the springs and checked the lifters and rocker arm. He also looked at the valves with an optic cam.
 

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Discussion Starter #45
@The_big_dill

I'm calling it a misfire because of the PO301 code. The brand new fuel injector is getting a pulse, but the PCM is instructing the car not to give fuel to the #1 cylinder at low idle. The misfire is created by the computer which has picked up a problem. The spark plug is definitely good. We swapped it out into another cylinder and it works.
 

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It initially passed a compression test. At the dealership, it failed and that's part of the reason they decided it was a worn cam lobe. I don't understand how a roller cam can get a flat lobe. I think it's something in the valve train on #1. I have a hard time believing it's a roller cam. I think it must be the lifter, spring, or valve. What's frustrating is that my mechanic had the engine apart and looked at all of that and tested the springs and checked the lifters and rocker arm. He also looked at the valves with an optic cam.
IIRC, there was no obvious damage until cam shaft was pulled in the other reported case.
If I could only remember who posted it, the search engine here leaves a lot to be desired - I can't find it right now.
That thread had pictures of the cam with visible damage to the lobes. It looked like they were not heat treated (hardened) correctly...
 

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As mentioned multiple times, on the 2004-2007 years, the fuel injection harness was moved from the driver side to the passenger side and should not be an issue for those years.

the issue for the earlier years (2001-2003) was the harness being over the exhaust manifold

Melted injector wiring harness 2003 Town and Country
http://forum.chryslerminivan.net/showthread.php/20804-Melted-injector-wiring-harness-2003-Town-and-Country?highlight=melted+fuel+injector+harness
Hi blknblu, Ours is a 2004 T&C 3.8L and definitely has the wire loom at the driver's side, just saying.
 

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You should post the build date of your van, I see a note on one of the fuel rail harnesses that says:
WIRING. Fuel Rail. . Up to 02/23/04.
Maybe that is why your 2004 is on the driver's side?

Hi blknblu, Ours is a 2004 T&C 3.8L and definitely has the wire loom at the driver's side, just saying.
 

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Hello all,

I am new here, and I really hope someone can help me. :) I hope this is the right forum.

I have a 2005 Town & Country with 128,000+ miles on it. About 4 months ago, the Check Engine Light came on and it developed a rough idle. Mechanic said it was showing code PO301--misfire on cylinder 1. There was a Technical Service Bulletin from Chrysler on this issue that said to change all the plugs and wires and then reflash the computer. This was all done and the misfire was still there with the Check Engine Light still on.

Mechanic then did the following (not necessarily in this order):
--Measured the idle at which the misfire disappears--it disappears at exactly the same RPM every time (around 1600, I can't remember exactly)
--Swapped out the #1 coil with one from another car that did not have the problem
--Did a smoke test
--Did a compression test of valves 1, 2, 4 and 6
--Visually inspected the valve spring and the rocker arm on the bank of cylinders with cylinders 1, 3, and 5 to make sure they weren't cracked or broken
--Measured the height of the lifters on that same size and the #1 lifter is the same height as 3 and 5
--Checked the crank case positioning sensor
--Replaced all the intake seals and gaskets
--Swapped out the fuel injector on cylinder 1
--Using carb spray, checked for vacuum leaks

After all these tests, he couldn't find anything wrong.

We then brought it to a dealership who said that it was a worn lobe on the camshaft. I disagree (and my mechanic agrees) that this is the problem because the misfire occurs only at idle (and disappears at exactly the same low RPM every time as noted above) and the misfire disappears as soon as I accelerate.

One other notes--this car does NOT have an EGR valve. The hose on the positive crank case ventilation is cracked and I though this could be a potential vacuum leak. But I disconnected it and plugged the intake up to check to see if this affected the misfire problem, but there was no change.

Does anyone have any ideas or suggestions? It drives and feels like a vacuum leak, but we've done everything we can think of to rule that out?

Thanks
I'm not a sharpshooter but here is my shot, burnt valve/valves or leaky lifter. Compression test is a very crude way to check, a real pro uses a leak tester, you see, if a valve is slightly bent or a little burnt, enough compression will escape at idle and high idle to reduce the speed of the crank, it is not a misfire but a lower power fire if you will, you feel it in your "butt dyno" and the ECU sees it as a greater time interval between signals from the crank sensor ; the lifter scenario is about leaking enough at idle when speeds are lower and time to leak is greater not lifting the offending valve enough so it doesn't fill the cylinder or evacuate it properly, at higher engine speed the oil flow and pressure increases filling the lifter and since the time to leak is shorter it doesn't leak enough the cause the misfire. Please do a "leak test" either you or a good mechanic, check oil pressure at hot idle, from 2005 to 2007 5W20 is recommended, I'll use 30 or even a light 40 but if it is too cold and if you drive short distances the oil will not get hot enough to fill the lifter (very long shot, but...), the stethoscope is invaluable to track lifter issues, please use it. To diagnose a worn cam just take the rockers, pushrods and lifters off from the bad cylinder and from a good one in your case 3 or 5, rotate the crankshaft by hand (get all the spark plugs out to ease the turning) until the lobes are pointing to the hole and measure distance in intake and exhaust, repeat on a good cylinder and compare measurements, also on a bad lobe it is common for the roller of the lifter to show signs of pitting, wear or deformation. It is incredible how nowadays just because the engines are computer controlled nobody checks mechanicals, if it is not detected by the OBD2 scanner is a mystery and the whole engine needs replacement.
 

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My 06 t&c 3.8 did the exact same. Missed at idle and would go away at speed. P0301 code, changed plugs, wire, coil every sensor except down stream O2. Compression was not great. Pulled heads exhaust valves did not look that great on the seat side so changed them and reseated them as well as the intake valves to clean them up. Before I installed the heads something told me th check the lifters so.... cyl 1 both rollers eaten up, like 10 grit sandpaper. 2 looked rough, 3 rough and the first lifter on 4 starting to go. Loked at the cam lobes and they were rough as well. Welcome to the 05, 06, 07 spun camshaft bearing! Increased oil pressures at speed helps support the cam and goes back down at idle.
Pull your intakes off, upper and lower, remove lower intake gasket, remove the lifter retainer 3 -10mm bolts hold down and remove the retainer one set at a time. Then pull out one lifter noting which way the oil hole is pointing so it goes back correctly. This wil let u see the roller on the bottom of the lifter and some of the cam shaft through the lifter location. If the cam ain't smooth, welcome to my world!
 

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443k3.3 what was the mileage on that 3.8 when all this happened?
 

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Mine went about 130-140k. About 3 yrs ago.
 

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So, as I understand the thread you still have a misfire on #1?

I don't see how a worn lobe/lifter can affect compression? As long as all valves are closed compression should be good. When a lobe/lifter fails the valve won't open. Maybe that only happens if an ex valve won't open, not sure about that one!!

Pls let us know what is happening, I have to know the outcome of this one!
 

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04anniv, I messed up the cam bearing on my 06 happend in dec 13 at 133k. Saving $ up for a new reman.
 

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04anniv, I messed up the cam bearing on my 06 happend in dec 13 at 133k. Saving $ up for a new reman.
I see. Did you buy this van new or used? Sucks man.
 

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So, as I understand the thread you still have a misfire on #1?

I don't see how a worn lobe/lifter can affect compression? As long as all valves are closed compression should be good. When a lobe/lifter fails the valve won't open. Maybe that only happens if an ex valve won't open, not sure about that one!!

Pls let us know what is happening, I have to know the outcome of this one!
If the intake valve doesn't open enough the amount of incoming air will be reduced, meaning low compression.
 

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Sorry I didn't know they re-routed the fuel injector harness away from the exhaust in Mar 2004+ vans. Still, I would inspect the wires to be sure, especially if a simple Velcro wrap like mine.

I also wonder how a bad cam lobe could greatly affect a compression reading. Air velocity is so low while cranking that the intake only needs to crack open to not cause a restriction. On my older carburetor engines, I have done a compression test both with throttle closed and propped open and never noticed a difference in readings. Additionally, it sounds like the engine runs fine at higher rpm so the valves must open well. I third the suggestion of a leak-down test. I do a poor man's version. I bring the cylinder to TDC (comp stroke) and apply air pressure via the hose from my Harbor Freight compression tester. That hose has a standard air fitting. I don't apply much pressure (~10 psi) so the engine doesn't spin (if not perfectly TDC). If you hear flow, try to find where it is coming out - intake or exhaust means that valve, resp., oil fill cap means rings. Those are easy tests to do before digging into the valve train again. The engine is a simple air pump, and you can verify that function with simple tests.
 

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I have to go along with Bill, I just don't think a low intake valve can make that much difference in compression testing. This is especially true if a preferred and more accurate leakdown test is used. Valves don't even enter into this test.

With ATs this is not so easy anymore, easy with aircraft though - just hold the prop!!

However, I am willing to be convinced.

I really want to see the solution to this mystery!!
 
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