Cold starting 1999 Jeep Cherokee will not idle when cold starting without keeping your foot on the accelerator, until engine warms up, then idles, and works just fine

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.

Change the temperature sending unit/temp sensor. When starting, the sensor will tell the computer to put the engine in cold start mode to give a bit more fuel and raise the idle a little so it WILL start and keep running without ever touching the throttle. Once warm-up is completed, this sensor will tell the computer to stop the cold start mode and go to normal run mode. THAT is your only problem.

Auto idle module may be bad or the idle valve on the engine may need to be cleaned.

Problem with cold weather idle

Wrong fuel octane water in fuel...

Your only problem friend, is the temperature sending unit/sensor. Upon cold start, this sensor wil tell the computer to go into cold start mode putting a bit more fuel in and raising the idle a bit to keep it running when cold without using the throttle. Replace that sensor and your good to go. Makes sense, right?

there is a rpm magnet that bolt on top of your transmission i had a jeep that done the same thing and repleced that and havent had a problem sinceits located on the left top side of your tranny has one little bolt that holds it in and a wire coming off of it that should fix your problem.

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.

Check the throttle position sensor"tps",or the idle air control "iac" by chance did the battery go dead or was unhooked?
if so the ecu was reset and needs to relearn idle settings by just keeping it running for a few minutes

many automobiles behave that way on a cold start, so you don't have to worry about it. just continue to rev the engine until it is warm!