I have a 88' Cherokee with a 97' engine and ever since i got it running it idles fine for probably 20 seconds or so then the idle gets rough and low for about 5 or 6 seconds then back smooth again. It doesn't usually crank up the first time I hit the key and it seems to get better when at normal operating temperature. What should I check?

 

Check your idle air control valve, remove it and spray it with carb cleaner, mine had similar problem and the ICV was super dirty...if cleaning does not fix it, the solenoid on the valve could be going out and just cant hold steady

 

Ok the ICV is on the throttle body right? Are there any ways to check it for proper operation?

 

Yes, it's on the throttle body and held by two screws. Not sure how to test it, my guess is that you could check resistance through the coil, but not sure you will be able to determine if it's functioning properly. I would just remove the two screws, pull it out, remove the oring, and spray it with carb cleaner, and reverse procedure. Mine was pretty dirty with a lot of black deposit. After cleaning it, the idle settled. The way the valve works is that the system feeds it a certain amount of current causing it to open or close, the part that you are cleaning acts as a valve to increase or decrease the amount of air allowed to enter the throttle body, when dirty, it's not a good seal. If your idle is still erratic after you clean it, it could possibly be that the coil inside the valve could be wearing out and that causes the valve not to hold steady...so it is moving in and out therefore causing your idle not to be steady...hope this helps.

 

Ok I will try that when I get a chance. Thanks!!

 

I cleaned the IAC and still have an intermittent idle but doesn't seem as bad as it was. What else can I check?

 

If you have tuned up everything else, it could be a bad IAC. Not sure how to test it, but assume you could hook it up to a variable power supply and should hold steady at a set voltage.

 

Ok i have the intermittent idle when cold but after I get to normal operating temperature it idles smooth.

 

Maybe somebody else can chime in here. I think the culprit is your valve. It maybe not be opening enough while cold, hence your eratic idle, but when normal operating temps, it's opening where it needs to be. Do the RPMs go up when you turn the a/c on to compensate for the load? When I cleaned my valve, I also cleaned the the area where the valve sits in. Since there was deposit on the valve, there was also deposit in that area.
Keep trying...you'll find it...

 

I took the throttle body off when I cleaned the IAC and cleaned the valve and where the valve seats really good. I don't have a/c right now.

 

I also noticed my jeep is running rich when the idle gets low and rough. Could this be the oxygen sensor?