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Codes P0171 and P0174

Tiny
IAMHOAGIE
  • MEMBER
  • 2006 JAGUAR XJ8
  • 4.0L
  • V8
  • 2WD
  • AUTOMATIC
  • 110,000 MILES
Car runs great for about eight or ten miles then check engine light comes on and when I slow down or stop than accelerate it smokes like a mosquito sprayer. I get a P0171 and P0174 codes. Don't think it is all the o2 sensors. Tried cleaning MAF than bought a new one. No change. Checked for leaks, can't find any. I cleared the codes and it runs great again. Until it goes about eight or ten miles than same thing all over. It's like as soon as a monitor resets it happens. The first drive cycle monitor is the adaptive fuel monitor. I can't figure out why it smokes so bad.
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Friday, April 26th, 2019 AT 5:11 AM

31 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
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
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Friday, April 26th, 2019 AT 5:30 AM
Tiny
IAMHOAGIE
  • MEMBER
  • 16 POSTS
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.
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Friday, April 26th, 2019 AT 5:34 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
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
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Friday, April 26th, 2019 AT 5:46 AM
Tiny
IAMHOAGIE
  • MEMBER
  • 16 POSTS
Not supercharged Scan tool: would that be freeze frame?
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Friday, April 26th, 2019 AT 5:59 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
No, it would be long term trim percentage for the O2 sensors.

Roy
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Friday, April 26th, 2019 AT 6:13 AM
Tiny
IAMHOAGIE
  • MEMBER
  • 16 POSTS
My scan tool only reads I M Readiness and Freeze frame.
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Friday, April 26th, 2019 AT 6:42 AM
Tiny
IAMHOAGIE
  • MEMBER
  • 16 POSTS
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.
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Friday, April 26th, 2019 AT 6:49 AM
Tiny
IAMHOAGIE
  • MEMBER
  • 16 POSTS
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?
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Friday, April 26th, 2019 AT 6:57 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Okay, you need a real scan tool to monitor these readings.

Can you get one?

Roy
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Friday, April 26th, 2019 AT 6:57 AM
Tiny
IAMHOAGIE
  • MEMBER
  • 16 POSTS
AutoZone might do it for me.
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Friday, April 26th, 2019 AT 6:58 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Yes, that is a free service. Have them print out all the readings for you from live data.

Roy
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Friday, April 26th, 2019 AT 7:00 AM
Tiny
IAMHOAGIE
  • MEMBER
  • 16 POSTS
Will do. I'll get back to you. Thank you for your time.
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Friday, April 26th, 2019 AT 7:01 AM
Tiny
ASEMASTER6371
  • MECHANIC
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You are welcome.

Always glad to help.

Roy
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Friday, April 26th, 2019 AT 7:05 AM
Tiny
IAMHOAGIE
  • MEMBER
  • 16 POSTS
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
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Friday, April 26th, 2019 AT 7:09 AM
Tiny
ASEMASTER6371
  • MECHANIC
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We are the same age. I teach this now and travel all over the country.

A big difference from when we started.

Roy
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Friday, April 26th, 2019 AT 7:20 AM
Tiny
IAMHOAGIE
  • MEMBER
  • 16 POSTS
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?
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Friday, April 26th, 2019 AT 3:50 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
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.
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Friday, April 26th, 2019 AT 4:08 PM
Tiny
OVERDUZCO
  • MEMBER
  • 1 POST
  • 2000 JAGUAR XJ8
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 70,000 MILES
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.
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Friday, April 26th, 2019 AT 5:54 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
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)
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Friday, April 26th, 2019 AT 5:54 PM (Merged)
Tiny
IAMHOAGIE
  • MEMBER
  • 16 POSTS
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.
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Saturday, April 27th, 2019 AT 1:49 PM

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