I have a 1998 XJ, 4.0, AW4 with 108K miles that is having an odd high idle problem. CEL codes thrown are 122,123,1694. I have searched previous posts and have changed my IAC valve (cleaned port too) and TPS. I have checked for vacuum leaks with a non-ignited propane torch. My TPS signal voltage is reading 1.04 (a bit high?) - 4.0 throught the range, without drop outs. The source voltage is 5.15 (again, a bit high?). My TPS ground is normal at 0 OHMS. The IAC and TPS are new OEM Mopar parts. I am going to start checking grounds, connections and intake/exhaust manifold bolts next. The ground strap from the rear of the block to firewall "appears" good, but it will be checked momentarily.
My symptoms are: High/bouncing RPMs after warming up to normal operating temperature. RPMs at idle in park or neutral are 1,000 - 2,000. Sometimes they stick at around 2,000 and sometimes they drop all the way down to about 450 for a split and immediately bounce up to 1,500 - 2,000. Sometimes the RPMs will just hang out at 2,000 at idle indefinitely and at other times they will bounce up and down from 450 (almost stalls) to 2,000 in fairly rapid cycles.
While driving I can feel the same cylcles occuring. I can feel the drop off, like my fuel or ignition has been turned off, but if I "mash" the throttle it immediately responds very well. They Jeep seems to shift well and at the proper times and has no trouble going 80MPH or more. If I keep the pedal down and the vehicle is accelarating the problem does not seem to present itself, however if I try to maintain a constant speed I can feel the "drop off" and "bounce back". It's not a "spit and sputter" type issue at all. It's more like and "on.... almost off.... then over compensate for almost stalling" type issue, if that makes any sense.
Any help would be greatly appreciated guys!
My symptoms are: High/bouncing RPMs after warming up to normal operating temperature. RPMs at idle in park or neutral are 1,000 - 2,000. Sometimes they stick at around 2,000 and sometimes they drop all the way down to about 450 for a split and immediately bounce up to 1,500 - 2,000. Sometimes the RPMs will just hang out at 2,000 at idle indefinitely and at other times they will bounce up and down from 450 (almost stalls) to 2,000 in fairly rapid cycles.
While driving I can feel the same cylcles occuring. I can feel the drop off, like my fuel or ignition has been turned off, but if I "mash" the throttle it immediately responds very well. They Jeep seems to shift well and at the proper times and has no trouble going 80MPH or more. If I keep the pedal down and the vehicle is accelarating the problem does not seem to present itself, however if I try to maintain a constant speed I can feel the "drop off" and "bounce back". It's not a "spit and sputter" type issue at all. It's more like and "on.... almost off.... then over compensate for almost stalling" type issue, if that makes any sense.
Any help would be greatly appreciated guys!