Dark Angel

The last 2-3 weeks I've been having trouble with my Jeep wanting to stall. It's been intermittent, and can drive just fine for days, then will "cough" all of a sudden. In the last few weeks, it's done this probably half a dozen times. Most times it's during or after idling. I haven't had any trouble at higher speeds, and only one time, during idling, did the "check engine" light come on. When idling, the idle goes along just fine until it coughs. When it coughs, I put it in neutral and give it gas and that seems to help. All the lights seem to be operating just fine.

Three months ago, I replaced the fuel filter (the one on the frame) because the Jeep was stalling then. Jeep ran fine until about 2-3 weeks ago.

I tried turning the key 3x to get the troubleshooting code, and if I looked at it right, it seemed to read 12-5-5, or 3-5-5 (which I can't find a code for). If the code was 12-5-5, then according to an online source the "12" stands for:

"12: Direct battery input to PCM was disconnected within the last 50 Key-on cycles."

So...my questions are these:

1: What could be causing the stalling problem?

2: What is "direct battery input to PCM"? and can/how does that cause a stalling problem?

My Jeep is a 1993 Cherokee Sport 4x4 with the 4.0L 6 cyl. engine. Thanks a whole bunch in advance for any and all tips/help.

belvedere

Code 12 just means the battery was disconnected recently. Code 55 means end of code list.

I would start with cleaning the IAC valve. You could also check the throttle position sensor and your fuel pressure.

Rockville

Every time you check codes, you should see 12 in the beginning and 55 in the end.

tjwalker

The #1 cause of stalling on the Jeep 4.0 engine is a marginal BATTERY.

And yes, you can have a battery that is strong enough to start the engine but marginal enough to give the engine management system fits and create stalling.

Have your battery LOAD TESTED. Any parts store will do this for you for free.

Rule the battery in or out before moving onto other possibilities like a dirty throttle body, idle air control, or other things. If battery checks out, try THIS.
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The Idle Air Control (IAC) is mounted on the back of the throttle body. (front for 87-90) The valve controls the idle speed of the engine by controlling the amount of air flowing through the air control passage. It consists of a stepper motor that moves a pintle shaped plunger in and out of the air control passage. When the valve plunger is moved in, the air control passage flows more air which raises the idle speed. When the valve plunger is moved out, the air control passage flows less air which lowers the idle speed. Over time and miles, the IAC can get carboned up which can have an adverse affect on idle quality. Cleaning the IAC may restore proper function and is an easy procedure to perform and good preventive maintenance so it is never a bad idea.

CLEANING THE JEEP 4.0 IDLE AIR CONTROL

Remove the air filter cover, associated hoses and the rubber boot that goes from the air filter cover to the throttle body. Remove the IAC with a torx driver (2 bolts; one can be kind of hard to get to)

“Gently” wiggle out the IAC from the throttle body. Gasket on the IAC can be re-used if it is not damaged

Clean the IAC with a spray can of throttle body cleaner; inexpensive and available at any place that sells auto parts. Throttle body cleaner is recommended rather than carburetor cleaner as it is less harsh, safe for throttle body coatings and is best for this task. Use cleaner, a rag and a toothbrush and or Q-Tips. Be gentle; don’t twist or pull on the pintle that protrudes from the IAC as it is fragile and you could damage it.

Thoroughly spray clean and flush where the IAC seats in the throttle body with the same spray cleaner

It is also a good idea to clean the entire throttle body itself, the butterfly valve inside of the throttle body and all associated linkage as long as you have things disassembled

Reinstall IAC and check idle quality

Dark Angel

Thanks a bunch, everyone. My battery is fairly new, and I remember it being load tested not that long ago. But I will have it done again, just to be safe. I will also clean out the IAC and see if that helps. I've owned my Jeep for 7 years now, and have never had to clean that out...so maybe it's due. Thanks again, everyone, for your advice. I'll let you know how it goes.

Dark Angel

Hi, everyone,

Well, I tried to remove the IAC valve...simple, just two screws, using a torx. However, discovered that the lower screw has apparently been fiddled with before I owned the Jeep, and the end of a torx was broken off in the screw. I can't get a dremel in the space to try to cut a slot in the head of the screw to remove it. Sooo...next step is to remove the throttle body...looks simple enough, just 4 bolts.

I am somewhat mechanically inclined for a girl...but whenever I'm doing something that I've never done before, I'm always scared I'm going to really mess up my Jeep. This time it's the throttle linkage that attaches to the throttle body. The Chilton manual says that I need to remove this linkage cable from the throttle body in order to remove the throttle body off the engine. But I can't find anything in the Chilton manual or online about how to remove the throttle linkage?

Also, the Chilton manual didn't say anything about this, but I'm going to err on the side of safety anyway and ask if I need to worry about spilling any gas or closing off any fuel lines while I do this?

I appreciate everyone's help so far...thanks so much!

Dark Angel

Update: I found this video on Youtube for a quick cleanup of the throttle body:


I gave it a try, and it's helped, but I'm thinking that I should probably still take it apart and clean it thoroughly. I did finally find info on the throttle linkage and how to remove it, too. My Jeep did do well on a test drive...I let it idle every chance I could while I ran a couple of errands. It didn't so much as sputter, and the idle seems to have smoothed out a bit and also come down a bit.

Thanks again, I appreciate everyone's help!