Originally Posted by 1998redxj

Got my cel checked today and the code po171 came up. That was the inly code. Truck is running like ****. Has a knocking sound and is going thru gas like its going outta style. As im stopped the rpm goes up and down. About a half a rpm also smells really bad. Did a full tune up 2 days ago and reset the computer after the tuneup was done. Teuck ran great for a day nd then went to crap on day 2. What should i do.

Originally Posted by CCKen

Here's P0171:

P0171-1/1 FUEL SYSTEM LEAN

Possible Causes:

RESTRICTED FUEL SUPPLY LINE
FUEL PUMP INLET STRAINER PLUGGED
FUEL PUMP MODULE
O2 SENSOR
O2 SENSOR SIGNAL CIRCUIT SHORTED TO GROUND
O2 SENSOR HEATER OPERATION
TPS VOLTAGE GREATER THAN 0.92 VOLTS WITH THROTTLE CLOSED
TP SENSOR SWEEP
MAP SENSOR OPERATION
ECT SENSOR OPERATION
ENGINE MECHANICAL PROBLEM
FUEL FILTER/PRESSURE REGULATOR (HIGH)
PCM

The PCM may be see a lean condition, as reported by the Oxgen Sensor(s) and compensating for the lean condition and causing a rich condition, which may be why you are seeing poor gas mileage and a smelly exhaust.

Was it running okay before you did a tune up?

First check the Oxygen Heaters fuse in the power distribution center (shown in the attached photo).



Then (money back) rent a fuel pressure test set from an auto parts store like O'reilly or Advance auto parts, and check your fuel pressure at the fuel rail. You should see 49.2 psi +/- 5 psi while the engine is running at idle, and as the throttle is advanced to about 1,200 RPM. If the fuel pressure is low, remove the 15 amp fuel pump fuse (shown in the pic) and replace it with a 10 amp mini fuse, then operate the pump again andsee if the fuse blows. If it does the pump is pulling too many amps (10 amps is max). Reinstall the 15 amp fuse. If your fuel pressure is too high it is a faulty pump regulator and the PCM is trying to pull fuel off causing the P0171 lean DTC.

Visually inspect the upstream oxygen sensor wiring where it passes over the intake manifold for chafing (common fault).

Is your engine oily/dirty near the upstream oxygen sensor? Are you using NTK or Bosch oxygen sensors? How old are the sensors? If you are using NTK sensors, inspect the ambient air vents in the body of the sensor for contamination. If they are plugged, or you have a cracked exhaust manifold in that area [knocking sound?], it may cause a rich or lean signal to the PCM, depending on the type of contamination. See attached pic.

Check your exhaust manifold for cracks.

If you have over 100K miles of the oxygen sensors you should replace them (NTK is the OEM sensors).

Inspect all wiring and connectors to your sensors and distributor for collateral damaged caused during the tune up.

Check these few things and get back. You may need to check your throttle position sensor and other sensors.

Originally Posted by 1998redxj

What o2 sensor should i replace? Upstream or down? Or both? I dont kno lol i really think its my o2 sensor. Everything else seems to be good. Cleaned the throttle body checked all fuses and grounds did a full mopar tune up. Like its trying to choke itself out when i go to stop at a stopsighn or light. Seems to be like the fuel ration is off cuz its running so damn rich

Originally Posted by 1998redxj

Yes it is my daily lmao but ive been using another car to get around till i get this fixed lol. So im prolly gonna order them both today and as im waiting for them to get in ill work on getting the old ones out so i can pop the new ones in as soon as they get here. Hope this solves the problem. I also just realized i have a hole in my muffler about the size of a quarter. Can that be making it run bad also?

Originally Posted by CCKen

Does the new looking O2S look like the one in post #3. That's a NTK O2S.

Originally Posted by 1998redxj

Yes but has no air vents. So i guess its not the oem one. Im gonna just order both up and down streams.