Ok so my 92 Cherokee 4.0 has been overheating since I bought it. I have replaced everything under the hood with no success. I finally gave up and took it to a mechanic who tells me that it is running extremely lean but can't seem to find out why. Do any of you have an idea where to start other than the O2 sensor and fuel filter? Oh yah it runs strong and the CEL is not on.

I could really use some help on this one,

Mark

 

A little more info please. What did you replace? Is it actually overheating or just running hot? How many miles?

 

Here is what I have done for the cooling system
3 row CSF radiator from radiator barn
Hesco hi flow water pump
Hesco hi flow thermostat housing
OEM 195 tstat
upper and lower hoses
heater control valve
heater hoses
fan clutch
serpentine belt
Radiator cap 13lbs stock and 16lb just to check
new Autometer water temp gauge
B&M trans cooler I also bypassed the radiator
Plugs cap and rotor wires and air filter.

I have also checked the compression all 6 were around 145
had a block test done no gasses in the coolant.
no water in the oil and no oil in the water
electric fan is wired to a switch which is on all the time.
I have checked under hood temps with an IR gun and all temps towards the front of the engine seem ok, its only hot back where the sending unit is and around the back of the motor. I have flushed the motor several times with chemicals and with the Prestone kit.

 

This may sound stupid/simple but is there a chance you have an air pocket in the cooling system?

 

Thanks for the tip but I have burped it several times and there isn't any air in the system.

The mechanics computer is showing that the fuel trim is at -10 on bank 1 which is running lean.

 

Actually, a -10% trim is showing that the PCM is trimming fuel off (note the negative (-) sign), which indicates there is a rich mixture that is being compensated for. If the fuel trim was a positive number, like 10%, the PCM is adding fuel to compensate for a lean mixture.

-10% sounds like a long term fuel trim number.

Read this for FYI, and print it off and give it to that mechanic that said it was extremely lean.

http://www.magnaflow.com/07techtips/...in/TB80010.pdf

 

......and what temps do the new gauge and temp gun indicate?

 

Have you ever figured this out I'm having the same exact issue

 

You are responding to a post that is 7 years old. The OP hasn't been on the forum for over 5 years. I'm pretty sure he isn't going to help you.

Please post your own thread.

 

You mentioned O2 sensors. How long since yours have been changed?