High Idle when warmed up. 95 Grand cherokee 4liter. i can let off the gas and the vehicle will accelerate up to 30mph stays at about 1500rpms idling

It likely has EFI (electronic fuel injection) and an idle air control valve that regulate idle speed. They can get gummed and fail to have a fast idle when cold, or get stuck the other way, and have a too fast idle all the or regularly take its time slowing down after you take your foot off the gas. An engine temp sensor can also cause a lingering high idle if it reports the engine as still being cold after warm up.

Check the coil packs or individual coils, fuel injection flush at sears where they actually do a flush. Check fuel filter too.

Good luck

Because you disconnected the battery you lost the long trim value,you will now have to relearn the idle,start the vehicle idle it to 1500 RPM,hold for a minute,idle should stabilize,turn on A/C let it idle,for a minute,now your done,

Most vehicles run at a high RPM for a couple minutes until they are warmed up, and then it should drop down to normal idle speed.

usually rough Idle is not noticable at high ildle. Once it is idles normally try Disconnecting one injector at a time. If the idle stays the same than that cylinder is the culprit. Remove that spark. If it is wet than do a compression test. Should read better than 100lbs of compression.If compression is good take a spark plug and hook it into the end of the plug wire.Lay it across the intake,start the car and watch for spark. If you have spark than you probably have a bad injector. A miss will cause the vehicle to idle high. The computer is trying to keep the car from dieing out. Hope this helps. No spark do a tune up.

jeep is known to have faulty oil pressure switches,check that first,if it's good then you have a weak oil pump.










TIM.........

check the fuel pressure on the fuel pump

The idle relearn needs reset. Keep your foot on the gas at about 900 rpm. Make it idle for about 5-6 minutes. Slowly ease up on the gas until it will idle on it's own, it might take a while. After you get it to idle, it might be idling real low, but on its own, Let it sit and idle until for 20 minutes. After that it should be back to normal. You will have to do this every time you have the battery unhooked for a while.

could be an idle controll sensor...maf sensor or o2 sensor....run a good carb/fuel ingector cleaner through with with some high test gas, do this for you next 2 fill ups, one can of cleaner per full tank...if it doesnt work.. then one of those senors is playing tricks with ya...In worst case the timing belt is slipping..
hope this was helpful !

could be either EGR valve stuck open or the IAC(idle air control)