Cylnder Pressure - - Stalling

I have a 1990 240sx with 150kms on the engine.

Recently it has been stalling when the weather is getting hot out. Here are my cylnder pressure readings..

C1, C2, & C3 -------- 150
C4 -------- 50

Becuase i am running on 3 cylnders will that cause the engine to stall when it gets hot out?

also, before it stalls the car jerks alot then it will just stall.

does anyone know what could be the problem?

thanks