How JustAnswer Works:

  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.

Ask lexpert Your Own Question

lexpert
lexpert, Lexus Master tech
Category: Lexus
Satisfied Customers: 9973
Experience:  Master Certified with lexus, 8 years experience with Lexus
Type Your Lexus Question Here...
lexpert is online now
A new question is answered every 9 seconds

1999 LEXUS: P0171..MAF..MISFIRE IN CYLINDERS 2,4,6 AND 8 AT TIMES BUT

Resolved Question:

1999 LEXUS GS 400 HAS A CODE P0171. I SPRAYED THE ENGINE WITH CARB CLEANER,NO PROBLEM FOUND.I, REPLACED THE MAF BECAUSE IT WAS READING BELOW SPECS.REPAIRED A CRACK IN THE AIR INDUCTION CHAMBER.I AM READING MISFIRE IN CYLINDERS 2,4,6 AND 8 AT TIMES BUT NO P0300 CODES
Submitted: 4 years ago.
Category: Lexus
Expert:  lexpert replied 4 years ago.

Thank you for using just answer.

What are the fuel trim readings on bank 1 and 2 long and short term?

I feel like I am missing part of the story here.....what repairs were done on this car right before this issue?

Where exactly did you find this "crack?

Customer: replied 4 years ago.

REPLACED AIR FILTER,CRACK WAS IN THE AIR CHAMBER BOX NEXT TO THE AIR FILTER COVER

Expert:  lexpert replied 4 years ago.
Please answer all questions above so I can properly help you.
Customer: replied 4 years ago.

I DON'T KNOW FUEL TRIM

 

Expert:  lexpert replied 4 years ago.
You stated code #'s above so by this I assume you have a scan tool and know how to use it correct? Does this scan tool have data lists also?
Customer: replied 4 years ago.
YES, I DON'T HAVE THE CAR RIGHT NOW
Expert:  lexpert replied 4 years ago.

I will need that to help you further.

Did this car recently have a starter replaced by chance?

Customer: replied 4 years ago.
NO
Expert:  lexpert replied 4 years ago.
ok, get me fuel trim readings when you can
Customer: replied 4 years ago.

OK, IF THE SHORT TERM FUEL TRIM IS LOWER THAN THE LONG TERM THAN WHAT OR THE OTHER WAY AROUND

 

Expert:  lexpert replied 4 years ago.
Get me data and I can offer you the assitance that you are paying for, I do not play any guessing games or give guestimates, thank you
Customer: replied 4 years ago.
ok.how do I get back with you
Expert:  lexpert replied 4 years ago.
Just reply as you are doing right now, there should be a few e-mails in your inbox also to direct you back here, I am mostly online in the evenings, there is another excellent expert here by the screenname of skyvisions that is on during the day and can help you at that time if needed also. I want a list of short term feul trim readings at idle, when revving the motor up and under a load on BOTH banks, thanks
Customer: replied 4 years ago.
ok thanks
Expert:  lexpert replied 4 years ago.
ok
Customer: replied 4 years ago.
DID YOU GET THE SPECS
Customer: replied 4 years ago.
hey Peter short term fuel trim 2.3 long term 34.4
Expert:  lexpert replied 4 years ago.

Hello again, I just came online.

Clarify these specifications?? Are these from bank 1 or 2 and in percentages?

Customer: replied 4 years ago.
hi. bank 1 and 2. I perform a smoke test no leaks. checked fuel pressure 28 psi at idle isn't that low
Expert:  lexpert replied 4 years ago.
Ok, so the short term % is toggling around zero but at 34.4 long term then correct? What do these values change to when you drive or put it under a load? As last stated by me last night I need values at idle, revving motor and also under a load, thanks
Customer: replied 4 years ago.

at 2000 rpm bank 1 st trim -2.3% lttrim 24.2 bank 2 st 1.6 lt 27.3 uder load bank 1 st4.7 lt 23 bank 2 st2.3 lt 23.3 the misfire went alway when i checked fuel pressure

Expert:  lexpert replied 4 years ago.
Question for you so I can better explain here....do you understand how fuel trim calculations work and what they mean?
Customer: replied 4 years ago.
short term is whats going on and long term is correcting it.if short term # XXXXX XXXXX the vehicle is lean
Expert:  lexpert replied 4 years ago.
Short term is supposed to be around zero on this car, yes long term is correcting but it takes longer for these values to change.....if you are reading near zero on short term this means you are not duplicating the issue currently, this is most likely happening when the car is actually driving. Yes your fuel pressure reading is low, the specification on this car is 44-50 psi when the pump is commanded on and the system is also designed to HOLD pressure above 20 psi once the car is shut off. I would be checking fuel issues at this point if the idle speed is normal and the 02 sensors are responding normally.
Customer: replied 4 years ago.
yes o2 sensor working correctly.yes fuel pressure was holding for 5 mins
Expert:  lexpert replied 4 years ago.

you said fuel pressure was 28 psi though did you not? Did you mean this when running or engine off?

Customer: replied 4 years ago.
running and it was holding pressure for 5 mins
Expert:  lexpert replied 4 years ago.
ok, so pressure when the fuel pump is ON is 28 psi is that correct?
Customer: replied 4 years ago.
yes
Expert:  lexpert replied 4 years ago.
That reading is too low, as I stated above with the pump energized specification is 44-50 psi.
Customer: replied 4 years ago.
ok,that why when i removed the fuel pressure pulsation damper the vehicle stopped misfiring
Expert:  lexpert replied 4 years ago.
My thoughts on this would be to check the fuel pressure regulator on the rail, if this is sticking or bad it can cause pressure issues on this bank of the engine and cause the issues you are describing. I believe you are trying to describe this same part by "dampener"....the round shaped cylinder with the float needle in the middle and the plastic cap on it.
Customer: replied 4 years ago.
yes, it's two, one for each banks.I thought itwas to damping the pulsation in the fuel line.the fuel pressure regulator is with the fuel pump in the tank
Expert:  lexpert replied 4 years ago.
There is a regulator on the pump that holds pressure in the line when the pump is not running but the "pulsation dampeners" also play a vital part of the fuel delivery to each bank, you said the issue went away after you removed this to check pressure, I assume this came back once reinstalled correct?
Customer: replied 4 years ago.
yes, just the misfire went away and i was starting to feel the misfire come back but the po171 was still there
Expert:  lexpert replied 4 years ago.
Your questions to me have been crystal clear and very well worded but every reply I get from you to a question I ask is only 50%, you need to be clear in your replies to my specific questions please
Customer: replied 4 years ago.
sorry about that ,you have been very helpful ,thank you.how do i contact you to let you know the problem is repaired??
Expert:  lexpert replied 4 years ago.
you can just log back in here and reply as you are doing now, I carry a blackberry that is linked to the site but am mostly only available in the evenings, I woudl probably swap the 2 "dampeners" and see if you have any change. Also try flushing the fuel rails, I have seen a lot of issues lately with fuel quality and e85 contamination that can get clogged in the injector ports.
lexpert, Lexus Master tech
Category: Lexus
Satisfied Customers: 9973
Experience: Master Certified with lexus, 8 years experience with Lexus
lexpert and 8 other Lexus Specialists are ready to help you

JustAnswer in the News:

 
 
 
Ask-a-doc Web sites: If you've got a quick question, you can try to get an answer from sites that say they have various specialists on hand to give quick answers... Justanswer.com.
JustAnswer.com...has seen a spike since October in legal questions from readers about layoffs, unemployment and severance.
Web sites like justanswer.com/legal
...leave nothing to chance.
Traffic on JustAnswer rose 14 percent...and had nearly 400,000 page views in 30 days...inquiries related to stress, high blood pressure, drinking and heart pain jumped 33 percent.
Tory Johnson, GMA Workplace Contributor, discusses work-from-home jobs, such as JustAnswer in which verified Experts answer people’s questions.
I will tell you that...the things you have to go through to be an Expert are quite rigorous.
 
 
 

What Customers are Saying:

 
 
 
  • THANK YOU, THANK YOU, THANK YOU!! I've got my baby back. Tomorrow I will get a tank of high octane, remove the top, go for a long long ride and enjoy my car. THANK YOU! Jughead USA
< Last | Next >
  • THANK YOU, THANK YOU, THANK YOU!! I've got my baby back. Tomorrow I will get a tank of high octane, remove the top, go for a long long ride and enjoy my car. THANK YOU! Jughead USA
  • Wonderful service, prompt, efficient, and accurate. Couldn't have asked for more. I cannot thank you enough for your help. Mary C. Freshfield, Liverpool, UK
  • This expert is wonderful. They truly know what they are talking about, and they actually care about you. They really helped put my nerves at ease. Thank you so much!!!! Alex Los Angeles, CA
  • Thank you for all your help. It is nice to know that this service is here for people like myself, who need answers fast and are not sure who to consult. GP Hesperia, CA
  • I couldn't be more satisfied! This is the site I will always come to when I need a second opinion. Justin Kernersville, NC
  • Just let me say that this encounter has been entirely professional and most helpful. I liked that I could ask additional questions and get answered in a very short turn around. Esther Woodstock, NY
  • Thank you so much for taking your time and knowledge to support my concerns. Not only did you answer my questions, you even took it a step further with replying with more pertinent information I needed to know. Robin Elkton, Maryland
 
 
 

Meet The Experts:

 
 
 
  • lexpert

    Lexus Master tech

    Satisfied Customers:

    2100
    Master Certified with lexus, 8 years experience with Lexus
< Last | Next >
  • http://ww2.justanswer.com/uploads/LE/lexpert/2012-6-14_21259_Ja2.64x64.jpg lexpert's Avatar

    lexpert

    Lexus Master tech

    Satisfied Customers:

    2100
    Master Certified with lexus, 8 years experience with Lexus
  • http://ww2.justanswer.com/uploads/SK/skyvisions/2012-6-9_23736_JACropped3.64x64.jpg Skyvisions's Avatar

    Skyvisions

    ASE Certified Technician

    Satisfied Customers:

    1329
    Lexus Expert
  • http://ww2.justanswer.com/uploads/DR/drivefast1971/2012-1-12_172422_0009051tQKh.64x64.jpg Ron Z.'s Avatar

    Ron Z.

    - Lexus Tech -

    Satisfied Customers:

    250
    18+yrs experience. State Inspector and Lexus Diagnostics
  • http://ww2.justanswer.com/uploads/AM/amdhcds/2012-4-1_04039_3911361015044607312849462040349387767831419345287n.64x64.jpg AMD's Avatar

    AMD

    Master Technician

    Satisfied Customers:

    229
    L1 Advanced Level Diagnostics Specialist
  • http://ww2.justanswer.com/uploads/joecamel90/2008-11-13_03615_head_shot.jpg George H.'s Avatar

    George H.

    ASE Certified Technician

    Satisfied Customers:

    164
    15+ years ASE Master w/L1 Drivability certification
  • http://ww2.justanswer.com/uploads/CA/caprio23/2011-12-13_155550_20111213105344.64x64.jpg Anthony's Avatar

    Anthony

    ASE Certified Technician

    Satisfied Customers:

    117
    ASE Master Automobile Technician with over 20 years exp. in this field.
  • http://ww2.justanswer.com/uploads/RO/rodcuda/2011-7-25_224114_Donhoff1.64x64.JPG Neal's Avatar

    Neal

    Mechanic

    Satisfied Customers:

    114
    Shop owner experienced in most brands.