I own a 1996 Jeep Classic

2WD
4.0 inline 6

my issue is, very rough idle in the morning like its cold...

Very rough idle even after its been running, but after its sat for two hours...

an occasion black smoke from the tail pipe...

spark plugs are gaped properly, no foul plugs...

I have no clue how to fix this...HELP!

 

try cleaning the iac motor and its mounting hole

 

1. Ensure tuneup parts are fresh. Plugs, plug wires, cap, rotor

2. Cleaning of the idle air control and throttle body is never a bad idea. They get carboned up over time and miles

3. If you have ever seen a check engine light, pull stored codes for guidance.

4. Black smoke may indicate a "rich" mixture. The two sensors most suspect for contributing to a rich mixture IMMEDIATELY at start up would be the coolant temp sensor and the map sensor. Both can be tested with a meter and a manual outlining the exact procedure.

 

When I had the first of the rough idle issue, it did throw a code of a bad coolant sensor....

So I will replace that...

I have checked the plugs they seem normal wear no darkness of fouled in any way...
I did go and buy some throttle body spray cleaner and shoot it in the slit for IAC, that helped I believe...

Im worried now, I let the jeep sit for most of the day yesterday prior to getting my wife from work....

The jeep started right up no idle issues...

Started it this morning ( cold morning)...it had no issues...

So now I'm wondering, can a sensor issue be intermidiate?