Hello all!

I have a very annoying issue with my 2003 x-type 2.5.

I bought this car from my brother last June. It had sat in my mouse-infested yard, up until a month ago.

Prior to parking it for several months, the only thing it needed was a CV shaft (rotted tone ring.)

So anyway, it has recently developed an intermittent misfire on cylinders 2, 4 and 6. It is producing codes p0352,354 and 356. The odd thing is, it misfired when I put it back on the road a few weeks ago, so I did a quick visual inspection and found the bank 1 upstream o2 sensor wire insulation had been chewed up. So I replaced the o2 sensor and the car ran perfect (for a little while.)

Fast forward to yesterday (mind you, I let the car sit for the last few days, as we had a decent size snowstorm 3 days ago.) the jag is misfiring again!

I immediately suspected snow melt had gotten into a connector/wiring harness somewhere. I immediately started checking everything over. Couldn’t find any chewed/damaged wires. Even took off the ground in front of the strut tower and the ground on the top side of the alternator and cleaned both-made no difference. At this point, the sun had gone down and I decided to call it a day.

I decided to start the day off today, by starting the car. Much to my surprise it ran perfectly…until I took it for a drive that is. Approximately 2 miles into my trip, it started misfiring again. Same 3 cylinders. It has been misfiring since. No matter how many wires I wiggle, grounds I clean, coils I unplug and plug back in nothing seems to stop the misfire, except for letting the car sit for a few hours.

any possible ideas? Thank you in advance!

 

It's a pain, but you might want to move one or more of the back three coil packs into the front bank to see if the fault code shifts to the other cylinder.
That might prove if it is coil related without you having to start buying parts.
Spark plugs could be a maintenance thing you want to do, but it is unlikely that 3 on the same bank would all misbehave in this manner.
If your rocker cover is leaking you could have oil in the plug wells, that will cause misfires, so too water of course.

The O2 sensors are disregarded by the ECM during the engine warm up phase, as the ECM is running in "open loop mode" and just referring to its default fuel mapping tables until such time as the exhaust manifold and Cats starts to have enough temperature in them to become effective.
That might explain your decent "cold" engine behavior, but then after the ECM closes the sensor loop to take actual engine readings you are getting the change occur.
You could still have a bad reading from the upstream or downstream sensor for that bank that is upsetting fueling of those cylinders. The upstream and down stream sensors are different, but are interchangeable with corresponding front bank sensors again if you are wanting to see if you can move the fault.
A problem with any of the intake manifold sensors would likely not generate issue with just one bank.
Deformed manifold O rings can cause misfires, but again that would be more of a constant or on high engine vacuum creating more bypass.

Hope my ramblings help in some way. Good luck.