Having light bulbs burned is not what I'd call a faulty car. From what I read, he had only one problem with the check-engine light and a plastic tube that was leaking (probably the plastic got dry and failed). For a turbo car that's not a diesel, I'd say that he had a clear history.
The faults listed are similar to those experienced by me in the 1st 2 years and 20,000kms. Now 12 years later the car runs like a dream, ever reliable and relishing the regular 3-5000km trips made each year. Now registering almost 210,000kms on the odometer.
I put the Volvo S40 T's reliability down to the quality of the product, 'Mobil 1' oil changed every 10,000km and keeping the car well away from mechanics, performing all scheduled maintenance by the book personally.
1999 Volvo S40 1.9t, just bought the car with 96,000 miles on the clock. Volvo service up to 80,000.
The main problem I have so far is engine coolant temp sensor FAULT. Bad starting when hot, running poor, i.e. low turbo boost etc, caused by the etc, as the ignition, plus fueling is all over the place, and the air con fan and radiator fan are on all the time, due to faulty etc.
Going into Volvo next week, to have it sorted! When it's fixed, I'll have the smile back on my face, LOL.
Otherwise it's a nice car. Handles great, fast go cart really ,with air bags and sips, LOL, LOL.
Back to the Volvo S40 T4, lost power again completely. Due to the recent rich fueling problem caused by the engine coolent temp sensor faulty and bad MAF sensor!!
Volvo had the car for 3 hours and could not find out why my car was lacking boost pressure and power!! And I told them it was blowing black smoke at high rpm. So I did some research myself!!.
Car was blowing black smoke from exhaust!! No engine check light was on the dash, poor acceleration, lack of turbo boost.
I scanned the ECU with my obd11 reader, to find that the front lambda sensor was switching really slow, not only that the car made more exhaust sound from the front rather than back! I also noticed that the exhaust gas was weak from the tail pipe!! This was because the catalyst was partly blocked, causing too much pressure to build up back to the outlet manifold, slowing down the turbine wheel on the turbo, also leading to burnt gases going back into the engine.
Now after spending 500 pound on a new catalyst and front and rear lambda sensor. My Volvo S40 T4 is a flying machine again!!
So next time you have problems with your car, spend more time with it, learn about it. Listen to what the engine sounds like. and check exhaust gases.
I have 1998 Volvo V40 1.9 T4, and last couple of weeks something strange happens, similar to what you describe. The car runs great when cold. Once it gets above 90 degrees C, it starts losing power when I am pushing it to the max. Around 3500-4500 RPM it starts to raise the RPM slow, as if a sensor is saying the air is too hot, poor on oxygen, do not spray a lot of fuel? Maybe the boost becomes less or I do not know. My T4 has digital dash and it goes to 105C degrees when idling on one place and it is 40C degrees outside. Is this normal? I read the ECU with some demo software, not very professional, and also with another full version, but again not Volvo professional, and both resulted in something like O2 sensor heater fault .... trim something. This means the lambda heating and the mixture of air to fuel should be the trim. Spark plugs were replaced with Denso Iridium Tugh VK20Y, but one cracked so I replaced it with a used Iridium IK20. The rare misfires stopped after the cracked spark was replaced, but the loss of power under full throttle when car is running hot is still a problem. Please consult if you have any ideas?