COMMON XJ PROBLEMS
CRANKSHAFT POSITIONING SENSOR (CPS)
-The CPS gives the engine reference points for firing. When your CPS fails, due to exposure, vibration and oil saturation, there will be no RPM reference signal to know when to fire, therefore causing a rough idle, or hard starting or other issues. The CPS is located on top of the bell housing kind of on the driver's side. You can replace it from under your XJ.
THROTTLE POSITIONING SENSOR (TPS)
-The TPS moves with the throttle and sends a voltage signal to the computer giving throttle and speed info. A failing TPS will cause hesitation and stumble while accelerating, engine running too rich, or too lean, it also has input into the transmission for shifting points. The TPS is located on the throttle body to the right of the air inlet tube. See the picture to the right.
The oil pressure sensor is located on your distributor. A lot of time's when your Cherokee isn't showing any oil pressure this is the culprit. They just go bad or get broken when messing with the oil filter. Easy to fix and cheap to replace.
If you have trouble with starting in Park or Neutral or if your reverse lights no longer come on every time when selecting reverse gear then blame it on the Neutral Safety Switch or NSS. Most of the time they only need to be removed, taken apart, cleaned and re-assembled with new dielectric grease. Sometimes only an adjustment is needed. Usually by loosening the top adjustment bolt and the NSS turned clockwise as far as it would go, then retighten the bolt.
COMMON LEAK AREAS
-Exhaust manifold crack and leak
-Valve cover gasket
-Oil pan gasket
-Transmission pan gasket
-Rear main seal
-Front and rear axle seals
-Differential cover gaskets
-Rear yoke seal
-Brake bleeder screws
-Metal preformed brake lines
--Rear wheel brake cylinders
-Inline fuel filter and fuel line located on driver side above rear axle
