1991 Cherokee 4.0 intermittent hesitating at low RPM
 

1991 Cherokee 4.0 intermittent hesitating at low RPM

MY 1991 Cherokee hesitates sometimes at around 1k-2k RPM, other times it drives fine. I replaced TPS, ECU, plugs, plug wires, coil, distributor cap/rotor, Crank Position Sensor, MAP, Coolant sensor, fuel pump/filter, O2 sensor. Cleaned throttle body thoroughly. I ran the injectors into a bucket and all have clean bell-shaped spray. Theres no engine codes. Also I don't see any EGR controls.

Only thing left is idle air valve and distributor pickup.

Anyone know the cause???

Wow, it looks like you replaced a bunch of stuff. Did you pull the idle air valve to clean it? It looks like there isn't much left to swap...what about the catalytic converter...

Did you check for any vacuum leaks?also 91 is the first year xjs did not have an egr,or knock sensor.

i know this may seem kind of funny maybe kind of jew jew or moejo but take the negative terminal and positive terminal off the battery and rub them togather for about 20 seconds and then wait about 15 min or so before hooking them back up what this does is disscharge all the capacitors in the car some times you might clear the computer by just disconnecting the battery but other times this needs to be done one more thing you might try is checking all of the fuses in the fuse box just make sure that there isnt any that are blown some times if a sensor goes bad or shorts out it has a back up plan (fuse)just to make sure that your 5 volt system doesnt get feed 12 volts you might also check to make sure that your spark plug wires are not touching including the coil wire
hope this has been some help

1991 Cherokee 4.0 intermittent hesitating at low RPM
 

HI,

I checked all the fuses and cleaned all relay and large fuse connections as well as large under-hood grounds. I did clean the Idle Air Valve. I am going to replace the IAV and IAT sensor tomorrow. Special thanks to Pick Your Part. :)