Engine Performance problem
2000 Jeep Cherokee 6 cyl Four Wheel Drive Automatic 96000 miles
I have been having a problem with my jeep cherokee since last fall. It is all stock.
I was getting 21mpg if I tryed, and about 19 if I did not. Now I am getting 12-14mpg no matter what I do.
It all started with my catalytic converter going out(which I knew from the Check Engine Light). I sat on it for a while until I built up enough funds to replace it. Within a few months I watched my mileage go from 21, to 17, to 15, and to now, which is where it has stayed for some time.
I replaced the catalytic convertor with a high-flow one(magnaflow) and replaced both o2 sensors(which were due soon anyways). That did nothing.
Since then I have:
-Ran fuel injector cleaner through it
-Replaced plugs and boots
-Replaced air filter
-Check fuel pressure(which was 43)
-Tires are at 39psi
-Cleaned the throttle body
-Replaced the IAT sensor
-Checked for fuel leaks(none found)
-Checked for exhaust leaks(only one and it is past the last o2 sensor)
-Checked for dragging brakes(none found, the vehicle is pushed and coasts easily)
-Performed routine mantinance
-Checked for vacuum leaks(one was found coming off the cruise control unit, and fixed)
-Idle's and perfomes fine
-I use Shell Gasoline
-Coolant temp is fine(210, and marked at 208 via computer)
-Have reset the ECM after any sensor replacements
-Changed the rear differential lubricant and the transfer case lubricant
I am really at a loss at this point, no codes are being thrown by the computer, and I had the vehicle hooked up to a computer at a shop to see if they could see anything abnormal. Everything was fine, the only problem was that the engine though it was running lean so it was sending more fuel. There is soot on the tail pipe too.
Please help, anything is appreciated as this is becoming very expensive for me.
have the same problem?
Friday, March 26th, 2010 AT 12:31 AM