Volvo: Engine Management System Warning light, mass air flow sensor, mass air flow

Question
Hi. We have a Volvo v70 2002. Last week the car was driven a couple of miles when engine reduced its speed to 30 mph, we couldnt get speed up at all. Rev counter will only got to 2000 revs and no more. idle is very lumpy like an old tractor. We managed to get the car home, put it in the garage and left it. Since then I have been surfing the internet for any symtoms/ answers to help get rid of this problem. This is the first time this has happened to us. After spending a couple of hours surfing th internet for problems similar to ours. I then read about the Mass air flow sensor potentially causing this problem so embarked on sourcing out a new sensor. I have to add just b4 purchasing a new sensor I read we needed to try out the theory by starting and running  the engine until it gets warm then disconnect the MAF sensor to see if it righted itself, however, the problem had got worse as we could not get the engine to idle at all, it just kept stalling. we then disconnected the sensor, we had idle but lumpy. So we decided to get the sensor and also 5 new shiny plugs. we had a full service on the vehicle 6 months ago, but when we looked at the plugs they were the originals. So £250 service was for and oil filter and a bit of grease on the doors. Today the MAF sensor arrived and also the the shiny new plugs. They are all fitted and yes you guessed it stll the same problem?????????????? nothing has changed. Husband is now looking at the Lambda-sond to see if that is the problem. I must say we are not idiots when it comes to cars and mechanics, however,  we are not very good at fault finding. If something drops off we can sort it. Can you pleeeese point us in the right direction b4 I have to take a second job just to cover the cost of parts!!!!!!!!!!!

Answer
Karen,
You will need to read the fault codes and follow the faults. No way to know if you are on the right track. Many things affect the running of the engine. MAF is one, plugs is another, throttle housing software download is another, vacuum leaks, low fuel pressure.
Best thing to do is take it to a shop that really knows Volvo or the dealer.