Fresh P0174 code...

[LCM'06]

Greetings, all. I'm new to the forum, but not to the Liberty. Here's the skinny - my wife was just starting on a 550-mile trip in her 2006 3.7 Liberty when she saw the CEL illuminate. Continued the trip without catastrophic incident and made it home fine, but the Jeep used about twice the fuel it normally would on this trip.
Took it to my FLAPS yesterday to use their scanner, and the only code stored is a P0174, bank 2 too lean. A little study on the code helped me rule out some of the symptoms, which I hope will also help narrow down the possible causes...
Hooked a vacuum gauge to one of the ports high on the intake, behind the throttle body, and saw a rock-steady 16" of vacuum. Idle speed seems low, dash tach shows about 600 rpm, which may account for the low vacuum. But even that slow, it was smooth and solid. Also, coolant temperature never rose past the middle of the gauge, right where it usually stays.
Since P0174 is particular to bank 2/right side, I'm leaning in the direction of a failed upstream O2 sensor reporting lean and the PCM dumping fuel through the right side injectors to "compensate" for a non-existent condition. Has anyone here encountered this collection of symptoms with a P0174? Any insight/advice would be greatly appreciated. Thanks in advance - Chris

 

[DadOSix]

Greetings, all. I'm new to the forum, but not to the Liberty. Here's the skinny - my wife was just starting on a 550-mile trip in her 2006 3.7 Liberty when she saw the CEL illuminate. Continued the trip without catastrophic incident and made it home fine, but the Jeep used about twice the fuel it normally would on this trip.
Took it to my FLAPS yesterday to use their scanner, and the only code stored is a P0174, bank 2 too lean. A little study on the code helped me rule out some of the symptoms, which I hope will also help narrow down the possible causes...
Hooked a vacuum gauge to one of the ports high on the intake, behind the throttle body, and saw a rock-steady 16" of vacuum. Idle speed seems low, dash tach shows about 600 rpm, which may account for the low vacuum. But even that slow, it was smooth and solid. Also, coolant temperature never rose past the middle of the gauge, right where it usually stays.
Since P0174 is particular to bank 2/right side, I'm leaning in the direction of a failed upstream O2 sensor reporting lean and the PCM dumping fuel through the right side injectors to "compensate" for a non-existent condition. Has anyone here encountered this collection of symptoms with a P0174? Any insight/advice would be greatly appreciated. Thanks in advance - Chris

Chris :

Greetings and congrats of FLAPS. Took me a minute or 5 to get that!

Before you rush parts changing, check the basics like wiring and grounds. These old beasts have corrosion issues with wiring and insulation and such.

If you do decide to change sensors, be sure to use the good ones. OEM is best. I think if you search here a bit, you will find NGK as an acceptable replacement as well.

Agree that a bad upstream can cause dumping fuel. Could also be injector. (so back to nasty wiring). There is a ground strap from the firewall to the back of each head that 'looks ok' but really flakey around the connections.

Good luck!

 

[LCM'06]

Chris :

Greetings and congrats of FLAPS. Took me a minute or 5 to get that!

Before you rush parts changing, check the basics like wiring and grounds. These old beasts have corrosion issues with wiring and insulation and such.

If you do decide to change sensors, be sure to use the good ones. OEM is best. I think if you search here a bit, you will find NGK as an acceptable replacement as well.

Agree that a bad upstream can cause dumping fuel. Could also be injector. (so back to nasty wiring). There is a ground strap from the firewall to the back of each head that 'looks ok' but really flakey around the connections.

Good luck!

Thanks, Dad'! Good advice on the grounds and wiring. I will be looking at these items in the process. My rationale for being ready to condemn the right upstream O2 sensor, and nothing else at this point, is that for now the DTC is isolated to the right side; MAP sensor seems like it would show on both sides, and manifold vacuum at idle, as well as idle speed itself, was too stable for me to suspect a vacuum leak.
All this makes me wish I had spent more money on a better diagnostic computer when the tool slingers would visit my shop and price-fight for the sales. And paid closer attention in engine performance class...
Good job figuring out the FLAPS. It's not original material. I lifted it from another forum after I figured it out there; figured I had earned it with my superior braininess. I work at my parts store part-time and it's a bigger part of my life than maybe it should be.
Still open to any other input - I overlook stuff more often than I would like to admit! Thanks again, hope to post again soon with a success story - Chris

 

[LCM'06]

As promised, the latest... Replaced the right upstream O2 sensor this afternoon. Got in to drive to my parts store (where they wear the green shirts) and clear the codes, and upon starting the engine, the CEL was dark and the idle speed was right around 900 RPM and steady. Time will tell, and the code still needs to be erased, but my inclination is that the fuel consumption issue is gone for now. The downside is that I'm pretty sure I found that the oil loss from the engine is through the rear main seal. Ugh. Still open to info, advice, funny stories, ridicule, whatever you have... Until next time - Chris

 

[Xterra4x4]

Greetings, all. I'm new to the forum, but not to the Liberty. Here's the skinny - my wife was just starting on a 550-mile trip in her 2006 3.7 Liberty when she saw the CEL illuminate. Continued the trip without catastrophic incident and made it home fine, but the Jeep used about twice the fuel it normally would on this trip.
Took it to my FLAPS yesterday to use their scanner, and the only code stored is a P0174, bank 2 too lean. A little study on the code helped me rule out some of the symptoms, which I hope will also help narrow down the possible causes...
Hooked a vacuum gauge to one of the ports high on the intake, behind the throttle body, and saw a rock-steady 16" of vacuum. Idle speed seems low, dash tach shows about 600 rpm, which may account for the low vacuum. But even that slow, it was smooth and solid. Also, coolant temperature never rose past the middle of the gauge, right where it usually stays.
Since P0174 is particular to bank 2/right side, I'm leaning in the direction of a failed upstream O2 sensor reporting lean and the PCM dumping fuel through the right side injectors to "compensate" for a non-existent condition. Has anyone here encountered this collection of symptoms with a P0174? Any insight/advice would be greatly appreciated. Thanks in advance - Chris

Did you check 02 sensor?

 

[LCM'06]

Did you check 02 sensor?

Xterra4x4 - in a word, no. I would normally perform a post-mortem evaluation on a failed or replaced component, or compare it to its intended replacement. However, since the condition reported by the ECM (bank 2 lean) did not match the actual circumstances, and the fresh sensor turned the CEL off, I didn't bother. Plus, the new O2 sensor cost me about a third of what a walk-in would pay, so it was an acceptable gamble to me. And, finally, I don't know which wires carry the signal OR what the values should be. Still need to roll some miles under the car to verify it's actually fixed, too. Just been to busy with life-stuff...

 

[Ksat]

What's FLAPS?

Are you able to check the fuel trims? This would help confirm if the problem has been corrected. Running too rich or lean can cause additional problems (fuel wash, cat damage, etc).