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 Tim's Auto Repair Your Own Question

Tim's Auto Repair
Tim's Auto Repair, Mechanic
Category: Car
Satisfied Customers: 12443
Experience:  Have owned a repair shop for 25 yrs.
Type Your Car Question Here...
Tim's Auto Repair is online now
A new question is answered every 9 seconds

1989 GMC truck 350 TBI. loading excessive feul at idle. backfires

Resolved Question:

1989 GMC truck 350 TBI. loading excessive feul at idle. backfires until I get moving good then it runs great. Gives excessive feul code. Changed idle air,coolant temp. There is no cataletic converter just a pipe in place of it

Submitted: 7 months ago.
Category: Car
Expert:  Tim's Auto Repair replied 7 months ago.

Tim's Auto Repair :



Hi,My name is Tim,


I will do my best to assist you

Tim's Auto Repair :

please tell me the code you are getting

Customer:

45 excessive feul

Tim's Auto Repair :

hi

Tim's Auto Repair :

sorry i missed you

Tim's Auto Repair :

there are a couple of other things you may want to check here

Tim's Auto Repair :

1-the map sensor

Tim's Auto Repair :

2-the ecm[computer]itself

Tim's Auto Repair :

i will give you some tests/checks you can do for the 45 code that may help you find your problem

Tim's Auto Repair :

 
















30_gmtda405003068-002.png
Full Size Image

Code 45 - Rich Exhaust Indicated










58_gmtda405003068-001.png
Full Size Image

Wiring Diagram For Code 45 - Rich Exhaust Indicated





CODE 45 - RICH EXHAUST INDICATED


Circuit Description:

The ECM supplies a voltage of about .45 volts between terminals "D6" and "D7". (If measured with a 10 megohm digital voltmeter, this may read as low as .32 volts.) The oxygen sensor varies the voltage within a range of about 1 volt if the exhaust is rich, down through about .10 volts if exhaust is lean.

The sensor is like an open circuit and produces no voltage when it is below about 315~C (600~F). An open sensor circuit or cold sensor causes "Open Loop" operation.



Test Description: Numbers below refer to circled numbers on the diagnostic chart.

1. Code 45 is set when the oxygen sensor signal voltage or CKT 412:

^ Remains above .7 volts for 50 seconds, and in "Closed Loop".
^ Engine time after start is 1 minute or more.
^ Throttle angle greater than 2%. (about .2 volts above idle voltage)

Diagnostic Aids:

Using the "Scan", observe the block learn values at different rpm and air flow conditions"Scan" also displays the block cells, so the block learn values can be checked in each of the ceils to determine when the Code 45 may have been set. If the conditions for Code 45 exists, the block learn values will be around 115.

^ Fuel Pressure - System will go rich if pressure is too high. The ECM can compensate for some increase. However, if it gets too high, a Code 45 may be set. See Chart A-5 thru A-6
^ Leaking Injector
^ Check for fuel contaminated oil.


^ HEI Shielding - An open ground CKT 453 (ignition system reference low) may result in EMI, or induced electrical "noise". The ECM looks at this "noise" as reference pulses. The additional pulses result in a higher than actual engine speed signal. The ECM then delivers too much fuel, causing system to go rich. Engine tachometer will also show higher than actual engine speed which can help in diagnosing this problem.
^ Canister Purge - Check for fuel saturation. If full of fuel, check canister control and hoses.
^ MAP Sensor - An output that causes the ECM to sensor a higher than normal manifold pressure (low vacuum) can cause the system to go rich. Disconnecting the MAP sensor will allow the ECM to set a fixed value for the MAP sensor. Substitute a different MAP sensor if the rich condition is gone while the sensor is disconnected.
^ Pressure Regulator - Check for leaking fuel pressure regulator diaphragm by checking for presence of liquid fuel in the vacuum line to the regulator.
^ Check for leaking fuel pressure regulator diaphragm by checking vacuum line to regulator for fuel.
^ TPS - An intermittent TPS output will cause the system to go rich, due to a false indication of the engine accelerating.

Tim's Auto Repair :



If you are satisfied with my answer,Please Rate my answer by clicking the rating button so I can get credit for my work..I'm not always going to be giving you good news, so please don't let this stand in the way of you accepting my answer. .it does not cost you more money and we will still be able to communicate, ,.please understand, i can not see, hear or touch the vehicle and only know what you tell me. Bonuses and positive feedback are appreciated.. if you are not satisfied with my answer, please do not leave bad feed back ,i will gladly opt out and let another expert handle the question. .if i have sent any diagrams, ,please print them. .sometimes you may need to right click the image [,then save picture as]to save it to your computer so you can open it with your picture program...Please ask if you need more help


Customer:

I put new injectors in today. New EGR ,Pressure reg N feul inj. kit . It runs better. I did this on my own but I asked ya so im a man of my word so I have no problem paying for what I asked for even though I perfomed the work with no answer. Thank You. Rob R Close

Tim's Auto Repair, Mechanic
Category: Car
Satisfied Customers: 12443
Experience: Have owned a repair shop for 25 yrs.
Tim's Auto Repair and 15 other Car 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:

 
 
 
  • I would (and have) recommend your site to others I was quite satisfied with the quality of the information received, the professional with whom I interacted, and the quick response time. Thanks, and be sure that I'll be back whenever I need a question answered in a hurry. Stephanie P Elm City, NC
< Last | Next >
  • I would (and have) recommend your site to others I was quite satisfied with the quality of the information received, the professional with whom I interacted, and the quick response time. Thanks, and be sure that I'll be back whenever I need a question answered in a hurry. Stephanie P Elm City, NC
  • used your service this weekend with "Trecers" help. thank you ,thank you, thank you. replaced an A/C fan motor. Local Auto Zone had part. $15.00 "tracer" fee and $40.00 for parts, I saved several hundreds of dollers at a shop. i will recommend you and use you in the future. David L. Richmond, TX
  • 9 dollars, 2 hours of my time, and I drove away. Your diagnosis was right on the mark. Thank you so much. Phil Marysville, CA
  • Lurch. Thank you very much. I had real doubts about this website but your promptness of response, quick followup and to the point answer with picture was incredible. Charles Walnut Creek, CA
  • As a single woman, I really appreciate an excellent and affordable opinion.
    Thank you Geordie, I will not hesitate to contact justanswer in the future!
    Sue Charleston, WV
  • Another great insight to what may be the problem. I will have my mechanic take a look at it tomorrow. Thanks again, Frank...you do indeed know your stuff. Jim Castleberry, FL
  • The nearest Volvo dealer is 160 miles away. Best $15 bucks I have spent in a long time! Paul M Corpus Christi, TX
 
 
 

Meet The Experts:

 
 
 
  • Chris (aka-Moose)'s Avatar

    Chris (aka-Moose)

    Technician

    Satisfied Customers:

    846
    16 years of experience
< Last | Next >
  • http://ww2.justanswer.com/uploads/MU/muddyford/2012-6-13_1204_1.64x64.png Chris (aka-Moose)'s Avatar

    Chris (aka-Moose)

    Technician

    Satisfied Customers:

    846
    16 years of experience
  • http://ww2.justanswer.com/uploads/TE/TedG/2012-6-15_14759_avaLarge.64x64.jpg Ted G.'s Avatar

    Ted G.

    ASE Certified Technician

    Satisfied Customers:

    1596
    20 years auto repair experience, ASE Master Tech, Mechanical Failure consultant, Expert Witness
  • http://ww2.justanswer.com/uploads/joecamel90/2008-11-13_03615_head_shot.jpg George H.'s Avatar

    George H.

    ASE Certified Technician

    Satisfied Customers:

    1311
    ASE Master Tech 15+ yrs, AAS Automotive Technology, Factory trained Asian specialist
  • http://ww2.justanswer.com/uploads/AM/amedee/2013-10-24_23656_Amedee1.64x64.jpg Amedee's Avatar

    Amedee

    ASE Master Tech

    Satisfied Customers:

    2367
    ASE Master Tech advanced level specialist
  • http://ww2.justanswer.com/uploads/SU/supermechanic/2013-8-23_03546_500.64x64.jpg Jerry's Avatar

    Jerry

    Master Mechanic

    Satisfied Customers:

    1906
    ASE master, 30+ years. All makes and models. Trouble shooter, shop forman, service manager
  • http://ww2.justanswer.com/uploads/CR/crzydrvr00/2013-11-3_12123_246347.64x64.jpg Richard's Avatar

    Richard

    ASE Certified Technician

    Satisfied Customers:

    942
    12 years Ford Lincoln/Mercury Jaguar dealership as a technician and shop foreman reparing all makes
  • http://ww2.justanswer.com/uploads/ST/Steve7654/2012-6-5_215929_japic800x660.64x64.jpg Steve's Avatar

    Steve

    Auto Service Technician

    Satisfied Customers:

    1980
    25+ yrs experience as a professional working technician; ASE L1 master technician