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Q: Weird Power Problems on 1996 Jeep Cherokee

I bought the jeep used in August '10 and found out how to do a self-diagnostic check with the key switches in the ignition.  I received the code 12 42 21.  Immediately afterward I tried to start the jeep and it would barely start.  I had to keep the rpms at a minimum of 2500 or it would die on me. After letting it die a couple times it started acting normally again. 

Since then it's done it a couple more times to me.  But after a couple times dying it starts acting normally again.  (Not in cold weather.)

In the middle of December I took it to the shop to get new tires, brakes inspected (the ABS light has been on since I bought it), and an alignment.  

The day after bringing it home, I jumped in, unlocked the doors from the inside, and went to start it, and it died.  I took the key out, put it back in, and immediately all the power went out.  I took the key out, power came back on.  Put the key back in, power out.  I got out, shut the door, waited for a minute or so and got back in.  It started up like nothing was wrong.  It's really frustrating - the shop has no idea what it is, and I really don't want to get stuck somewhere in the snowy mountains of PA this winter.

Any ideas?  Thank you so much in advance.
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I would start by inspecting the wiring harness from the instrument panel to the steering column. If your vehicle is equipped with a tilt column, pay particular attention to the area where the column tilts. Wire frequently break in that area. Also check the connector at the Ignition switch. Inspect each terminal for corroded, overheated or loose fitting terminals. An overheated power feed to the ignition switch is common. Signs of overheated terminals are discoloration of the terminal and the melting or deformation of the plastic connector.
As for your stalling issue, It sounds like you may have a dirty Throttle Body. A Dirty contaminated Throttle body will cause stalling especially on the first start up or when coming to a stop. This is because there is not sufficient air flow past the throttle plate when it is in the closed position and the Idle Air Control motor cannot compensate fast enough to prevent stalling. Remove the Air Intake from the throttle body and with the engine OFF, open the throttle and look into the bore. If it is coated with a Black oily residue, clean as follows.
1 04897156AA Mopar Throttle Body Cleaner
1 NPN Scotch Brite Pad, (Green) or soft Bristle Brush
1. Remove the throttle body from the engine;
2. Spray the entire throttle body bore and both sides of the throttle plate with Mopar Throttle Body Cleaner, p/n 04897156AA. This will remove the bulk of the contaminant.
CAUTION: This cleaner should only be used in a well ventilated area. Do not allow contact with skin or eyes. Rubber or butyl gloves and safety glasses are recommended. NOTE: Use only Mopar Throttle Body Cleaner, the use of other cleaning agents may damage components of the throttle body. 3. While holding the throttle open, use a small, (1” x 1”) piece of green Scotch Brite scuff pad, (or soft bristle brush), clean the throttle body bore and throttle plate, (including edges). NOTE: It is important that this cleaning procedure be performed thoroughly and completely. The edge of the throttle plate, and the portion of the throttle body bore where the throttle plate comes to rest are the most critical areas where the cleaning should be concentrated. These areas must be free of all deposits when the cleaning is completed. 4. Thoroughly clean the throttle body with Mopar Throttle Body Cleaner, p/n 04897156AA, and blow dry with compressed shop air. Inspect for any foreign material which may have been left from the cleaning process. CAUTION: Do not blow shop air pressure directly into the throttle shaft or throttle body housing holes.
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