Jeep Cherokee running rough low idle at 200-300 rpms
CF Veteran
Joined: Jan 2015
Posts: 1,381
Likes: 3
From: Southern Maryland
Year: 1991
Model: Cherokee
Engine: 1999 4.0L
Fuel pressure is mechanical. Either the fuel pump is bad or the pressure regulator is bad. You can isolate by pinching off the return line from the regulator--if pressure goes up to 40 or higher then the regulator is defective, but if pressure stays low then its a problem with the pump. Not sure if the RENIX era had the ballast resistor, could be defective too.
::CF Moderator::
Joined: Aug 2011
Posts: 43,971
Likes: 1,579
From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Fuel pressure is a real issue here. Did you not read my post above?
::CF Moderator::
Joined: Aug 2011
Posts: 43,971
Likes: 1,579
From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Fuel pressure is mechanical. Either the fuel pump is bad or the pressure regulator is bad. You can isolate by pinching off the return line from the regulator--if pressure goes up to 40 or higher then the regulator is defective, but if pressure stays low then its a problem with the pump. Not sure if the RENIX era had the ballast resistor, could be defective too.
Just now getting it cruiser, phone refreshing slowly. Done with MAP as that isn't the culprit after fixing that line. Pulled the IAC to double check it. Should I be able to gentle push and pull the plunger in and out on it? Also where is the return line on the regulator so I can check that as well while I have the fuel pressure gauge rented
CF Veteran
Joined: Aug 2010
Posts: 8,357
Likes: 103
From: Canton, MI
Year: 1999
Model: Cherokee
Engine: 4.0
Nooooooooooooooooooooooooooooooooooooooooooooooooo oooooooooooooooooooooooooooooooooooooooooooooooooo oooooooooooooooooooooooooooooooooooooooooooooooooo oooooooooooooooooooooooooooooooooooooooooooooooooo oooooooooooooooooo!!!
Fuel pressure is a real issue here. Did you not read my post above?
Fuel pressure is a real issue here. Did you not read my post above?
::CF Moderator::
Joined: Aug 2011
Posts: 43,971
Likes: 1,579
From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Just now getting it cruiser, phone refreshing slowly. Done with MAP as that isn't the culprit after fixing that line. Pulled the IAC to double check it. Should I be able to gentle push and pull the plunger in and out on it? Also where is the return line on the regulator so I can check that as well while I have the fuel pressure gauge rented
I use a PC.
So this app has a mind of it's own and works on it's own timeframe?
CF Veteran
Joined: Aug 2010
Posts: 8,357
Likes: 103
From: Canton, MI
Year: 1999
Model: Cherokee
Engine: 4.0
Just now getting it cruiser, phone refreshing slowly. Done with MAP as that isn't the culprit after fixing that line. Pulled the IAC to double check it. Should I be able to gentle push and pull the plunger in and out on it? Also where is the return line on the regulator so I can check that as well while I have the fuel pressure gauge rented
No.
The IAC pintle is pretty much solid if it is properly connected to the motor gearing inside of the IAC.


