Replacing the Throttle Position sensor in a Jeep Cherokee
Jennifer’s 1992 Jeep Cherokee has been acting up lately. It has had a severe stumble at times but the stumble has been intermittent and unpredictable. I was guessing an ignition problem so I ordered a Crown Tune up Kit. However before the Kit arrived, her Jeep took a very severe stumbling fit one morning. During this particular event, the check engine light came on. Code 24 came up. That translates to trouble with the throttle position sensor.
I took her Jeep for a test drive and found that just off idle, the engine would nearly die unless you pressed the gas pedal down further. Coming back to idle it would do the same. I had to let off the gas completely to keep it for dieing but then it would idle fine. There seemed to be two trouble spots in the throttle position sensor and as long as you avoided those, the engine would run fine. The trouble was, these two spots were nearly impossible to avoid in city traffic.
I looked up the replacement sensor. Advance Auto had
a BWD Throttle Position Sensor for under $40. I could sell one from Crown for $25 or so. However, I noticed that a 1996 ZJ had the same part number. I remember that there was a ZJ throttle body somewhere in my spare parts pile.
I had her drive her Jeep to my shop. She had some trouble to but was able to get it there. I found the manifold behind the barn and set about pulling the TPS off. It took a T20 torx. The bolts were slightly seized in the aluminum body so I used a pair of vise grips on the torx driver handle to get the extra leverage I needed to twist them out.
I looked at how the throttle tang engaged the sensor. There are two tangs inside the sensor that catch on the blade of the throttle shaft. Due to the preload of the spring in the sensor, you can’t just push it straight on. You ha to twist it a bit, slide it on the shaft and then rotate it to align the mounting holes. I was glad I had the spare throttle body to practice on before I tried it with the one on her Jeep.
I used the same vise grip trick to loosen the T20 bolts holding hers in place. I unclipped the wire and slipped the sensor off the shaft. I rotated the sensor slightly and then pressed it into place on the throttle body. I tightened the two bolts and then reattached the wire.
I started up the Jeep and checked for the stumble. I was very happy that it was gone. There was a high idle condition that lasted a minute or so but one it settled into the proper idle speed, the condition never repeated. I guess the computer was adjusting to the new TPS.
A road test showed that the stumble was completely gone and the Check Engine light did not return. I was very happy that the engine code came up when it did. Otherwise I would have been disappointed that the tune up did not cure the stumble. The tune up kit will still be installed but at a later date.
