Need help 1998 4.0

Post by **Brett** » Mon Oct 05, 2009 9:37 am

so randy what fixed your problem? Just curious.

Brett

Post by **shmoken875** » Mon Oct 05, 2009 10:30 am

Brett wrote:so randy what fixed your problem? Just curious.

Brett

In a long roundabout way I think it was just a fuse. My jeep only left the driveway about 4 times this summer and the day I left for the VTMTR/school I got a CEL. Went all weekend and down to Tech with it on and when I got to town the engine ran like crap. Codes read: high volts upstream O2 and downstream O2 and O2 heater failure. Like an idiot I replaced the O2 sensors before realizing the heater was actually just a 15A fuse. In trying to get the upstream out I stripped it and frustrated with schoolwork to do I took it to Auto Repair to have them do it. Instead of welding a new bung on they welded a nut on top of the messed up bung.

With it "fixed" I still had all 3 codes; found and replaced the 15A fuse and all codes disappeared instantly but it still ran like crap. Tried TPS, MAP, CTS, plugs, wires, cap, rotor and sea foam to no avail. The CEL again came on with high volts upstream O2 and running rich due to a lean condition. Then under the direction of captain trow I unplugged the upstream O2 and it ran fine. I cut off the nut and messed up portion of the bung and screwed the O2 sensor into the remaining good threads.........and the jeep ran fine.

With that nut welded on, the upstream O2 sensor was too far out of the downpipe to read correctly. To be honest I think my original O2 sensors were probably fine and it was just the fuse that I replaced AFTER the nut was welded on. Luckily I didn't spend too much money beyond the labor and unnecessary O2 sensors. I borrowed james MAP and TPS, and the jeep needed the plugs, cap, rotor, and sea foam.