Hello Ladies & gents,
I am finally reaching out to the Volvo community to see if any of you can help me with my issues I have endured on our S60, because it has grew above my personal knowledge and experience. So, first off this is what was going on. Everytime we would start our car it would have a very rough/hard idle till we would give her a few revs. During all this it was also throwing CE codes 0300 which I know have to do with ignition. So after watching a few youtube videos I found that it needed new spark plugs and coils which we bought and I replaced. After done the car seemed to start up and run a lot better, until after we let it sit after the test drive for 15 mins. The wife went out to start it up again to check and well you guessed it, a hard/rough idle again. Does anyone have any idea what's going on? Also, does anyone know why my anti skid check light keeps coming on?

 

The P0300 is a "generic" misfire code - saying one or more of the cylinders is randomly misfiring. Misfires are caused by either an ignition (spark) issue or a fuel/air mixture issue. So now that you replaced plugs/coils on a bet that it was ignition, the next things to look at are those that control fuel metering. Sidenote, my experience is that plug/coil issues usually present as an cylinder specific misfire unless you have something that can impact all the cylinders at once.. Did you inspect the MAF, throttle body, air intake boots/vacuum leaks, exhaust leaks etc? Did you notice anything odd about spark plug color when they were swapped out?

 

When I pulled the plugs they were black as if they weren't burning all the fuel or as if the vehicle was running rich. One thing I have noticed is that the hard/rough idle only happens when the vehicle is warm/hot. When the vehicle is cold it seems to start up and idle fine. In that instance to me sounds like a fuel pressure regulator. As if the vehicle is doing a form of vapor locking. But once the vehicle is started and the hard/rough idle is there a few pumps of the throttle and the issue goes away. I have noticed that it seems the vehicle is running on the hotter side as I am adding coolant every few days and I have checked everywhere and have found no leaks but rather thinking is boiling off out the overflow. When driving the car has great power and pulls with no noticable loss of power. I have not checked the MAF, throttle body, vacuum leaks or exhaust leaks but have listened for both exhaust and vacuum and haven't heard anything. I heard the best way to check for a vacuum leak is the spray WD-40 around your vacuum lines. If you have a leak it will rev up. I really appreciate all your info. Just trying to get my wifes car running properly. Oh, I have noticed the fuel mileage has gone down if that helps any.

 

Did you ever get this issue resolved? I’m having the same problem.

 

I'm sorry for the late response here but I ordered the parts and waited for them to come in. This morning I replaced the Solenoids and hubs for the intake and exhaust. I also replaced the MAF sensor. The car ran great for a couple of hours, then I attempted to go up a fairly steep hill and the issues returned. The check engine light didn't return but the rough idle and the jerking returned.

 

Run the test to make sure head gasket is OK.