starts roughly and doesn't heat
 

i have Volvo S40 2000 2.0T b4204T2 automatic with 181000km in. i have replaced thermostat, coolant sensor, intake air temp sensor and tested new MAF. car starts bad but cranks good and starts with difficult. the car itself heats only just over the 1st line if i drive and when it's parked it heats all the way up but starts running bad and almost stalls if i press gas pedal and try to move. it does not display any fault codes. timing belt is 27000km old and the problem only has been 10000km.

long cold cranking and misfires can be caused by a faulty fuel pressure regulator. The FPR is attached to the driver's side (right side looking at engine) of the fuel rail. A quick test is to pop off the s shaped vacuum line on the bottom of the regulator - if fuel leaks out, it means you have a torn diaphram which can cause extra fuel to suck into the intake.

i forgot to mention but i have already changed it and i have also put in a new fuel pump unit