98XJLB723

Past few months I've had some issues that I can't seem to figure out. 1998 XJ Sport


First is my check engine light is on, codes are showing a misfire in cylinder 3 and 4. Was concerned at first about a blown head gasket but I'm not seeing any oil or coolant mixed. Oil doesn't smell burnt and coolant is still green.

I threw the parts cannon at it over time since it had been a while since i did any work on it.


Replaced the spark plugs, wires, cap and rotor, tps and cleaned the throttle valve of carbon buildup, she started bucking when idling in gear so i swapped the iac, put in new injectors since the last time I touched them was 2008. A solenoid went out in the transmission, so since I had to drop the pan anyways I replaced all three and filter for transmission ( no signs of metal debris and no leaks after replacing). The catalytic converter had started rattling and since I was under there I decided to swap out the tailpipe as well. Replaced the o2 sensor close to the engine block as I saw some of the wiring was shred.


So currently the CEL is still on for the 3 and 4 misfire (attempted to clear but comes back randomly when turning on my jeep). There is randomly a bit of a rough acceleration, vibrating sporadically, but usually during the acceleration there is no vibration or rough goes smooth but it feels like it's taking off once I hit 30mph wanting to jump up to 40mph+ almost like it got a surge of air or fuel into it but my foot is steady on the accelerator. Otherwise she doesn't seem to have any issues.


At this point I'm questioning if it's the fuel pump (honestly believe it's the original) or some type of electrical (really hoping it's a faulty relay). Either way i'm at a loss as to what to check next so any guidance or insight would be greatly appreciated.


I probably shouldn't have tossed the parts cannon but I'll just say it was just overdue maintenance and tuneup..


Thanks in advance

LJ

tjwalker

Job #1 would be to run a compression test to see if something internal may be going on. Not that difficult to do and the gauge can often be rented inexpensively from many parts stores if you don't have one. How many miles are on this engine?

The compression spec for the 4.0 liter engine is 120-150 psi, with not more than a 30 psi variation between cylinders.

98XJLB723

Mileage is sitting a bit above 164k

Shumpa@aol.com

I had similar system reports. Replaced ignition Rail….fixed…
steve