1994 Jeep Grand Cherokee Engine Size : 4.0
Question: starts hard cold. Reaches operating temperature starts fine.check engine light comes on right before cold start.

Answer: The first thing to do is get a scan of the computer codes. Most of the large parts store chains will do this for free. This may give an indication as to what part of the emission system is having the problem. You would then need to have the fuel pressure checked. A weak fuel pump can cause this problem on your Jeep. Also check for carbon buildup in the throttle body bore and plate. Cold engine should have a high idle until it warms up, so if you have a problem with cold starting, it may be an idle problem related to carbon in the throttle or the idle control valve. Also check for a vacuum leak. A vacuum leak causes a lean condition. This will effect starting on a cold engine more than on a warm or hot engine.