Have a 2006 Volvo S40 2.4. Have just replaced the 5 spark plugs,5 ignition coil, all 3 of the Oxygen Sensors and just replaced the MAF Sensor. The car hesitates and runs horribly. Burns a lot of gas. The "Shift Up or Shift Down" warning light comes on with the purple Diamond also. What am I missing???? The car stiff runs terrible !!! HELP!!!!!!!

 

#1 - BEFORE you replace parts -

SCAN the car with an appropriate scan tool - you might get a code that will point you (or someone who actually fixes cars instead of replacing parts on a guess) in the right direction toward solving your problem.

What codes are stored?

 

P0304 and P0172

 

304 is a miss-fire on x cylinder - can you isolate the cylinder? Unplug the injectors one at a time. Which injector makes the idle change the least or the worst? What's the compression?

172 is a rich code - What's the fuel pressure? Does the fuel pressure reading on your scan tool (if yours gives you live data) match your analog gauge you attached? Perhaps the fuel pressure sensor is making the pump run too much - (bit not likely)

It would be unusual but not unheard of that an injector is leaking and causing both the miss-fire and the rich condition.