I have a early 2004 S40 with 105,000 miles. I bought it for my daughter and have maintained it very well. It is a very clean car. My daughter was home from college over the holidays so I checked her car over, changed the oil, etc. Her car has always displayed the P0015 code (VVT plunger) in the winter, but not in the summer. I took the plunger off and cleaned it spotless, checked the passages (clear), and normally I use 10 30 oil but this time put in 5 30 to see if that would work. I'm in N.C. so it doen't get that cold but we just had a cold spell for a week, in the 10s and teens. I noticed a green sludge on the top of the dip stick and the underside of the oil cap. Im thinking condensation, there is no coolant loss. While I was cleaning the VVt plunger, the plastic conduit around the wires going to this sensor broke apart from just touching it. I bought some new conduit and put it around the wires going to the plunger and the coolant temp. sensor and then on down the front of the engine. Now my daughter calls me a week later and tells me the temp guage shoots up to hot, then down to cold, the car lunges while waiting at a light and she almost hits the car in front of her. She says the engine speed raises and the car will go down the road without her foot on the gas. Then it will go back to normal. She checked and there is no coolant loss. Check engine light on and the codes are P0015 (VVT plunger), P0128 (coolant sensor), P0302 and P0304 (misfires). All these codes are related to the wires that I just put new wrap on and handled. Short in the wires? coolant sensor? What's making the engine rev up?
Thanks

 

Just a guess. I'm betting the coolant temp sensor suddenly going full cold causes the computer to raise the idle as if the engine were actually cold an in need of warming up. Like the first start on a cold morning. And based on your description I think you are correct assuming it's those wires somehow.

 

there are multiple dtc in the system. u need to fix them 1 by 1. first check if there are corrosions on the ect sensor?