Hey everyone, I just bought a 1998 Cherokee 4x4 4.0L and am having trouble with a rough Idle and briefly losing power as I accelerate it. The power loss issue does not happen when I am in park or neutral, only when in drive. I will get up to about 20 MPH and then the RPMs will drop but come back after I let off the gas and press on it again. the fuel pressure is reading 49 PSI while running and slowly bleeds off when not running (I checked about 3-4 hours later after it had been sitting and it was down to around 20 PSI). I had codes for the O2 sensors and replaced both down and upstream. I have also replaced the spark plugs and wires. but the rough idle and brief power loss still occurs. Air filter is completely clean.


Any help would be appreciated.

Might want to clean your IAC (Idle Air Controller). It's on the right side (viewed from sitting in the driver's seat) of the throttle body adjacent to the throttle position sensor. My 98's would not work even after cleaning so I replaced it and that cured the cold idle issue.

I tried that, it seems new and was pretty clean. I fixed the O2 sensor code, turned out to be a bad fuse. still have a rough idle. how can i test the TPS or the Crankshaft position sensor?