Codes P0171 and P0174

Good morning,

What color is the smoke?

https://www.2carpros.com/articles/engine-black-smoke

https://www.2carpros.com/articles/blue-smoke-from-engines-exhaust

https://www.2carpros.com/articles/white-smoke-or-steam-coming-from-the-exhaust-pipe

Roy

Blueish white. Not condensation, not oil or seal problem. I think it's from too much fuel being dumped in because of the lean condition. As soon as I clear the codes the car runs great no smoke.

If it were fuel, it would be black.

Running lean will not produce smoke, the 172,175 would be set.

Do you have a scan tool that can read the long term trims for me when the engine is smoking?

Is this a supercharged motor? If it is, that could be the issue with the smoke and the running?

Roy

P0171
Descriptor
Probable Causes
Fuel Filter
Fuel Injector
Leaking Exhaust Pipe
Leaking Intake Hose Between Mass Airflow (MAF) and Cylinder Head
Mass Airflow (MAF) Sensor

Not supercharged Scan tool: would that be freeze frame?

no, it would be long term trim percentage for the O2 sensors.

Roy

My scan tool only reads I M Readiness and Freeze frame.

I clear the codes and the car runs perfect for about eight miles then the check engine light comes on. O2 sensors have not set yet. It's like what ever monitor sets that quick is causing the problem. I don't think it is O2 sensors. I replaced the MAF. Can't find any leaks. and it's blueish smoke.

I could take it to AutoZone and have them use their scan tool to get me the long term trim percentage for the O2 sensor. What else would you need?

Okay, you need a real scan tool to monitor these readings.

Can you get one?

Roy

AutoZone might do it for me.

Yes, that is a free service. Have them print out all the readings for you from live data.

Roy

Will do. I'll get back to you. Thank you for your time.

You are welcome.

Always glad to help.

Roy

I am 67 years old. I have been working on cars since I was 13. Rebuilt several motors and always did my own work on my cars. I pop the hood on a car now days and I am lost. Lol

We are the same age. I teach this now and travel all over the country.

A big difference from when we started.

Roy

Hey Roy sorry about how long it took. AutoZone did not have live data. Neither did anyone else in this town. One shop had live data, but wanted to charge me $95.00. I am attaching a file. Please tell me if that is what you are looking for. Am I seeing an EGR or EVAP problem?

Specs for fuel pressure. 47 is too low as it should up in the 50's. Looks like you need a fuel pump which would also explain the fuel trim readings.

Roy

V6
Idle speed .................... 3.3 bar (47.9 psi)
Wide Open Throttle .................... 3.8 bar (55.1 psi)

V8
Idle Speed .................... 3 bar (43.5 psi)
Wide Open Throttle .................... 3.8 bar (55.1 psi)

V8, Supercharged
Idle speed .................... 3 bar (43.5 psi)
Wide Open Throttle .................... 5 bar (72.5 psi)

Fuel is supplied at high pressure to the injectors via fuel rail which incorporates a fuel pressure and a fuel temperature sensor. The ECM increases the fuel pressure to minimize fuel vapor formation to maintain fuel flow across the injectors. An inertia type fuel cut-off switch will cut power to the fuel pump module in the event of an accident.

the diag tool reports P0171/P0174. Can you explain nature of this problem and how to repair? Dealer service $145.00 an hour. Since the layoff, I'm only working part time and can't afford to fix at dealer.

A lean fuel condition can be caused by:

* Low fuel pressure due to a weak pump or leaky fuel pressure regulator. (use a fuel pressure gauge to check fuel pressure at idle)

* Dirty fuel injectors. (try cleaning the injectors)

* Vacuum leaks at the intake manifold, vacuum hose connections or throttle body. (Use a vacuum gauge to check for low intake vacuum)

* Leaky EGR valve. (Check operation of EGR valve)

* Leaky PCV Valve or hose. (Check valve and hose connections)

* Dirty or defective Mass Airflow Sensor (MAF). (Try cleaning the MAF sensor wires or filament with aerosol electronics cleaner. Do NOT use anything else to clean the sensor, and do not touch the sensor wires)

Hey Roy, I want to thank you for all that good information. Sorry for taking so long to get back to you, but I want to check everything and be sure before I tackle that fuel pump. It's one of the harder ones to do. If I have to, I'll cut an access panel under the rear seat. I checked the EGR valve, the injectors, I don't have a PCV per say,but connectors and hoses are all good. I have no leaks. I replaced the MAF. I don't have a schrader valve so it's going to be hard to check pressure from the pump. I went ahead and bought a code reader that reads live data. Paid $100.00 for it. What I did find is this. I pulled the fuel filter and it seemed a little clogged. I cleaned it out and blew it out. Checked the data and I now have 51 psi. I checked the fuel pressure regulator and pulled the vacuum line. No fuel or leaks and it had vacuum to it. When I checked the data with the vacuum line off, there was no change. The pressure should have jumped about 8 psi shouldn't it??? I hope that's the problem and not the pump.

Yes, it should have jumped. You do need a pump.

The filter will not lower pressure. It has a bypass if it gets clogged.

Roy

Not the pressure regulator???

No, not at all.

If you want to try it, replace it and see but it will not prevent the pump from reading normal pressure. It will bleed it down after shut off and allow too much pressure.

Roy

Okay Roy Thank you very much. I don't know how to decipher those numbers. I would have been off in a different direction, but you noticed the fuel pressure low. The car has about 115,000 miles on it and from what I have been reading, that's about when fuel pumps go out on those models. So thanks again I appreciate it, looks like I got a lot of work ahead of me.

You are welcome my friend.

Always glad to help.

Roy

Hello, I hope I am communicating with Roy. It's been a few weeks, but that is who I was working with. Anyway, I put a fuel pump in. As it turned out, the 2006 Jaguar XJ8 is one of the easiest fuel pumps to replace. The car runs great. Before, when I tromp on the accelerator the car would bog down, the check engine light would come on and it would smoke like hell and the Restricted performance message would come on. Now when I tromp on the accelerator, it takes off smooth and runs like it is supposed to. However the codes came back, P0171 and P0174. I am attaching a print out of live data. I know it shows fuel pump pressure at 47 but it can't be fuel pump the car runs great.

Okay,

The long term trims are too high.

Vacuum leaks, PCV valve or mass air flow sensor could be the cause of the codes.

Roy

Thank you. I got a new MAS air flow sensor, don't have a PCV, I better check for leaks. I'll let you know.

Sounds good. Keep us updated.

Roy

I replied to this but I don't think it went through so I'll do it again. Looks like you did it again Roy. I had a little rip in the rubber boot that holds the MAF sensor to the throttle body. I repaired it, let it sit overnight and drove the car all over town today and didn't get any codes. It didn't take much, that was a small rip. Looks like I got away cheap. Thanks again Roy you know your stuff.

Thank you for the kind words.

Always glad to help.

Roy