My 95 Grand Cherokee idles very rough for a few minutes after the first start of the day, then it smooths out and starts / runs fine the rest of the day. It starts up well, just misses and idles very rough for about 5 minutes. I have changed the spark plugs, and cleaned the throttle body and ICV valve. (I put in a new crankshaft sensor recently as well, and it ran fine for a few weeks until this problem developed). There are no warning lights showing and no error messages. Any ideas?

 

Put a fuel pressure gauge on the test port, start the engine and let it run for a minute, record the fuel pressure and shut the engine off. Let it sit over night with the guage still on the test port, in the morning check the pressure. It should not be at zero.

 

Which engine? If it's the AMC six, go through and retorque your manifold screws - they often work loose. Pay particular attention to the lower rear screws, and any screw that holds down both aluminum (intake) and steel (exhaust) - I could go into the reasons for the latter if you like.