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Discussion Starter · #1 ·
154K miles on my daughter's 2001 ATQ. will run great for a bit, then have misfires on the cylinders that are off the left-most coil (3 and 5).

1. coilpack was replaced 1-2 years ago.
2. bank 1 camchain tensioner was replaced a month ago.
3. timing belt was done this past winter.
4. plugs look good. assume wires are ok since it runs great most of the time...
5. codes will clear, and it will run great - took it for a test drive yesterday after looking over all of the wiring, and it ran fine (and I flogged it a bit). today it did it again, like it does every couple of days. went out and started it this evening when I got home, and it ran great, and had the following codes stored (discount the last one, she ran it until the low fuel light went on):
codes:
5 Faults Found:

16839 - EVAP System
P0455 - 35-00 - Large Leak Detected
16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 35-00 -
16687 - Cylinder 3
P0303 - 35-00 - Misfire Detected
16689 - Cylinder 5
P0305 - 35-00 - Misfire Detected
17658 - Fuel Level too Low
P1250 - 35-00

is it possible the P0455 is causing this? I am going to start with replacing the purge valve (replaced two years ago or so)...
 

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16839/P0455/001109 - EVAP System: Large Leak Detected 16839/P0455/001109 - Ross-Tech Wiki
This is not likely to cause misfires in 3 and 5 only, but should be fixed anyway.


If you used a Chinese coil pack, there is a high chance that could be faulty.
Check spark plugs and their gaps 1.6 mm (0.063"), swap plugs #3 and #5 with 2 other plugs.
Either #3 or #5 plug lead might be faulty, check both.
Check primary connector on coil pack.
 

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I wouldn't think the P0455 has anything to do Wirth the misfires. If it did it would not be limited to cylinders 3 & 5.

Likely the coil pack is the misfire issue since the misfires are confined to 3 & 5 and they are on the same leg of the coil pack. Probably moisture (condensation) on the faulty coil pack in the morning that dries out during the day so it runs fine in the afternoon? Might try misting some water on the coil pack.

If your like me, things you think you just replaced/repaired a year or so ago actually turn out to be 3-4 years ago. Time does go by faster, or my memory gets shorter over time.
 

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Discussion Starter · #4 ·
I wouldn't think the P0455 has anything to do Wirth the misfires. If it did it would not be limited to cylinders 3 & 5.

Likely the coil pack is the misfire issue since the misfires are confined to 3 & 5 and they are on the same leg of the coil pack. Probably moisture (condensation) on the faulty coil pack in the morning that dries out during the day so it runs fine in the afternoon? Might try misting some water on the coil pack.

If your like me, things you think you just replaced/repaired a year or so ago actually turn out to be 3-4 years ago. Time does go by faster, or my memory gets shorter over time.
I forgot to mention I misted the coilpack last night thoroughly. car ran fine this morning... it misfired this afternoon on the way home.

I looked at the plugs last weekend, and they looked fine - didn't use a feeler gage on them. I've run two bottles of Techron thru the car, as well, so it's not likely to be injectors (a common 2.8 problem - but not like *this* problem; when it starts misfiring, it misfires like constantly. a sticky fuel injector in a 2.8 that needs cleaning only misfires occassionally).
 

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Discussion Starter · #5 ·
16839/P0455/001109 - EVAP System: Large Leak Detected 16839/P0455/001109 - Ross-Tech Wiki
This is not likely to cause misfires in 3 and 5 only, but should be fixed anyway.


If you used a Chinese coil pack, there is a high chance that could be faulty.
Check spark plugs and their gaps 1.6 mm (0.063"), swap plugs #3 and #5 with 2 other plugs.
Either #3 or #5 plug lead might be faulty, check both.
Check primary connector on coil pack.
all good things to check. I was finding it hard to believe the Large Leak was causing any misfire, and especially not that 3 and 5.
coilpack is stamped "Made in China", so it might be cheaply made and the winding insulation might be breaking down with heat... and is not a cheap part to be swapping out. I will figure it out by this weekend, hopefully.
 

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Discussion Starter · #7 ·
Wires, Jay?
not saying this is going to be 100% of the time, but usually when wires fail, they fail 100% in my experience. this is an occasional misfire (although when it happens, it HAPPENS for both cylinders until the car is shut off for a bit).
 

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You most likely do have an intermittent open circuit in one of the wires or connectors.
Check the plug leads, the coil (which is wire), and the 3/5 wire from the ECM to the coil pack.
Any one of these will cause misfires in both 3 and 5.
 
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