I have a 93 ZJ, 4.0L. When I start my ZJ the RPM's shoot up to 2000 and it will slowly increase to 2200. While idling it will drop down in RPM's about every 30sec but it will drop only by a small increment and then it will continue to climb.

I recently changed all plugs, wires, distributor cap, rotor.

I have check for a vacuum leak (didn't find any). I have completely cleaned the throttle body, new gasket and gasket sealer for throttle body, change to a new IAC, Change to a new TPS (second time), checked all plugs.

On the back of the manifold (closest to the firewall) I found a vacuum hose that goes to the passenger fender then it went under the battery tray and stopped. When the engine is on this hose is drawing air. I plugged it and it had no change in my issue. Is this hose suppose to be connected to anything? I looked and didn't find any loose connections (hose). M<y vacuum diagram shows this hose going to "climate control, speed control, 4x4 axle".

Any ideas would be helpful

 

That hose connects to a vacuum reservoir under the battery tray. Is your A/C blowing through the defrost ducts only? That hose is the cause. With the engine running and the intake duct off, put your hand over the throttle body (be careful) and see if the engine stalls or keeps running. If it stays running, keep looking for a vacuum leak.

 

ty bustedback, ill check on this today

 

Ok, I got the mystery hose hooked back up (no change on start). I covered the rectangle hole in the throttle body (no change to the idle), I checked the hoses and canister for leaks (none found). Still no change, I still have a high idle (2000rpm) while in park, when I shift into gear rpm's drop to 1100.

Very frustrated

 

I have solved my issue, I got a throttle body from the pick and pull, installed and my Zebra runs perfect. The issue was ME, I didn't assemble the throttle body that I cleaned correctly, the butterfly wouldn't close all the way so the ZJ was getting more that it should......lesson learned, pay attention to details....lol!!! ty all

 

Never take the butterfly off of the shaft, you're only asking for trouble.

 

Yup, I know that now.....lol

 

Sounds like you have a vacuum leak