Chrysler Repair: P0300 and Wiring, 2004 chrysler sebring, chrysler sebring

Question
I have a 2004 Chrysler Sebring ~ roughly 95000km.  A few weeks ago, the engine light came on (flashing) and went away.  The code on it was P300 error/multiple cylinder misfire.  I reset the codes to see if I could duplicate the result with no luck.  The next day, I was in afternoon traffic when my dash went spastic.  ABS light, traction light, (!) light all started flashing, which was eventually joined by the engine light.  By the time I was able to find somewhere to turn in, I had lost power steering and my brakes and the engine shuddered to a halt saving me from a collision with a cement fence.  I tried to restart the car, which worked about 1 in 4 tries and only ran for a minute before cutting out again.  After a tow to my favorite garage, they showed me that they could duplicate my car cutting out by putting pressure on the fuse box, and after fixing a loose wire they couldn't duplicate it anymore.  The next day, I started my car and the engine light came on again with p300.  I took it back to the garage again.  They seem confident it has something to do with the wiring but don't know where to start short of replacing all of it, so they're not willing to get into it until it gives a more specific set of symptoms.  The error code flashes and goes off almost every time I start the car for the first time after not being used for several hours and always within 2 minutes of starting the car, accompanied with a loss of engine power (eg. pedal to floor and can't get above 50km/h  until engine bucks a bit).  After a few minutes driving improves but still seems a bit sluggish in places.  I don't mistrust my mechanics, but I am moving to go to college at the end of the month a five hour drive away and need a reliable car asap.  Is there anything I can do to help narrow down what it might be?

Answer
Thankfully you're OK after your rather exciting ride home. From reading the description of your problem I believe your mechanic are on the right track. Although I don't agree that the entire wiring harness will need replacement. The P0300 DTC, with no other relevant DTC's logged, is an indication that the PCM has seen something that has caused most cylinders to misfire but cannot find a singular cause for the condition. I would suspect that the fuel injectors and ignition coils are not getting enough voltage to operate properly. When your mechanics found some wiring concerns in the fuse box they were very close to the root of the problem. Ask them if they found any corrosion on the terminals that they fixed. If they did then its a sure bet that the corrosion has spread into the fuse box thereby causing a voltage drop in the ASD circuitry and maybe more. Hope this helps.