My New (Used) Jeep Cherokee Part III

I’m back. I previously mentioned about replacing the spark plugs, cleaning the injectors and so forth on my new (used) 2001 Jeep Cherokee. Well, even though I did all that, the idling was still a little rough. Not “ugly” rough, but enough to bother me some.

Since I had previously owned two Cherokees, I gained a little experience about these inline six-cylinder engines. By the way, I just love these engines; easy to work with, accessible, especially on the Cherokees and they don’t suffer as much from vibrations issues as V6 engines. With a little of TLC (tender loving care), these engines will be at your service for many years to come.

Well, back to the rough idle issue. From the experience I gained, especially from the 92 Cherokee, which I owned for 12 years, I knew that rough idling could possibly be caused by air-fuel mixture, spark plugs, oxygen sensor and/or vacuumed leaks problems. There are other possibilities of curse, but I wanted to start the troubleshooting with the easiest, most accessible and least expensive component.

I’m not a mechanic; well at least not a car engine mechanic. I retired from the Air Force where I worked as a jet engine mechanic and I currently work as a gas turbine engine technician, huge energy producing engines weighing over 400 tons; so you can say I’m mechanically incline. From experience I know that dirt can cause many problems to engines and it’s usually the best place to start when it comes to solving fuel system problems…you know, like dirty fuel filter, dirty fuel injectors, dirty air filter, dirty oxygen sensor, dirty throttle valve. Well, you get the point!

The idling on my 01 Jeep is controlled by the Idle Air Control Valve or IAC for short. It’s a very simple valve, controlled by an electrical solenoid. The biggest issue with the valve is carbon deposit, which can obstruct the air passage to the manifold. I decided this would be a good place to start. By the way, I’m not suggesting you take your engine apart to fix common problems. This is what I do because I like to take things apart and because by taking it apart, it would give me a better idea of the condition of other parts…but I had made many costly mistakes, so be careful.

I had already cleaned the engine. This is a good practice; it prevents dirt from getting inside your engine as you remove the components. The IAC mounts to the throttle body and the throttle body is easily accessible, so I decided to remove the throttle body itself. First, loosen all screws mounting the components to the throttle body; this makes it easier to remove these parts once the throttle body is removed…you don’t want to fight your way holding the throttle body while trying loosening the screws, as some can be really tight.

So here we go. I first disconnected all cables, including electrical connections, attached to the throttle body…no need to mention these cables here, they are easy to spot. I loosen all screws, you need a Torx-head screw driver for this (damn engineers), then I removed the four bolts holding the throttle body to the engine and, carefully, removed it. You may want to replace your seals and gaskets while at it, but I like to keep them if they are in good condition (hate to throw things away), so I tried not to break them as I removed the parts.

Once the throttle body was removed, I removed all the components attached to it; including of course the IAC, which once removed I noticed it was covered with heavy carbon deposits…a possible cause to my rough idling issue. However, it wasn’t the only part covered with carbon, as the butterfly valve inside the throttle body had plenty of it as well.

Once all the parts were removed, I proceeded to clean the components with throttle-body spray cleaner…don’t use carburetor part cleaning. Also, be careful not to get this chemical in your eyes, mouth or through a cut…it’s not good for you. Additionally, remove any o-rings from parts before spraying the solution…especially if you want to reuse them. One more thing, when cleaning the IAC, make sure the unit is upside down. You don’t want to spray this stuff inside the IAC body because the residue left behind may cause problems later on. I used a small brush, q-tips and a rag to aid in removing the carbon and used as little spray cleaner as possible.

By the time I was done, the throttle body and all its parts looked just like new. I reinstalled all the components, including the seals and gaskets and then installed the throttle body to the engine. After making sure all previously removed connections were back in place, I inserted the key in the ignition switch, crossed my fingers and fired up the engine.

And just like that, the idle issue was gone and my jeep was running as smoothly as ever. And not only that, but the throttle body and all its parts were as cleaned as a whistle…just the way I like it.

This is all for now. See you soon.