You did not mention if it is difficult to start when cold or hot so I assume it is when engine is cold.
Difficult starting with cold engine can be caused by:
1. Low fuel pressure. The pressure regulator or fuel pump check valve could be faulty resulting in low pressure at start up.
To test, turn ignition ON for 2 seconds and then OFF. Repeat cycle 3 times and try starting, if problem goes away, it is fuel pressure problem.
2. Engine Coolant Temperature sensor. The wrong signal sent by this sensor would result in the PCM providing the wrong starting signal.
3. Weak sparks. Ignition coil could be failing resulting in weaker than required sparks for starting.
4. Compression. If the compression pressure is low, cold starting would be affaected.
Tuesday, May 19th, 2009 AT 9:13 AM