check engine on 2002 Volvo S40

check engine light came on and had it checked and said cylinder 1 and 4 what does that mean

1 answer
What were the specific codes stored? Most likely a misfire in number cylinders 1 and 4. It could be many things, unfortunately and without experiencing the problem first hand or being able to do some basic diagnostic tests its hard to say.
A misfire could be caused by a mechanical problem (Low compression in a cylinder), it could be caused by a loss of spark (bad coil or spark plug) loss of fuel (bad fuel injectors) or a vacuum leak.