Usually there is a spark or fuel delivery issue when engines idle rough or don't start.
First, pull a plug after trying to start it, if it is wet, you are getting gas. However, it may be too much gas.
The next thing to check is the spark. Clean off the spark plug you pulled to check for gas, it is actually best to buy nesw plugs as if the plug looks black at all it may be gas fouled and will not spark, put the plug into the plug wire boot and ground the threaded area of the plug onto the engine. Don't hold it as it will shock you. Have someone turn the engine over and look for a good blue spark.
If this all checks out, some of the suspect issues to check are; fuel presssure, a dirty or clogged intake tract, a clogged catyltic converter, etc.
Her is a walk through on how to diagnsoe a vehicle that idles rough or won't start.
It is a link so just paste it into the address window of your internet browser;
Wednesday, October 5th, 2011 AT 8:35 PM