Question about 1999 GMC Yukon

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While driving down the road at various speeds, engine will surges upward 300-400 rpms on tackometer. nothing shows up on computer at GM dealer. replaced rotors, checked plugs, with no change in rpm surges. replaced transmission, torque convertor and still experiencing surge in rpm. Any ideas what is causing this problem? Yukon has 5.7 engine, 125,000 miles. HELP

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Problem throttle body or accelerator position sensor
there will be codes but it will need somebody experienced with the right scanner protocol to read them

Posted on Sep 12, 2017

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Posted on Jan 02, 2017

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Anonymous

SOURCE: 1998 Yukon high idle sound with bad gas mileage.

What you have is the torque converter clutch,cycling on and off.
When it is off.your rpm will go up and your milage will go down
First-check to see if your brake switch, on the back of the brake peddle, is loose or misadjusted. When you apply the brakes,the first thing to happen, is that you unlock the converter,so your trans is not connected directly to the motor,or you would stall. Then below 42 MPH,your trans is working off the converter, as a pressure multiplier ,based on rpm
Second- switch okey. You remove trans pan and change TCC Solenoid.

Let me know if if you need more guidance

Posted on May 08, 2010

Testimonial: "Thank you for the quick response. Figured it to be something with the trans. Gives me a good place to start and a good reason to clean out the other stall in my garage to work on it. Thanks again!!"

JOHN LAPIER

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SOURCE: 1999 GMC Jimmy SLT Engine light

What kind of a dealer are you going to . If what you are saying is correct the MIL light is on then what you need to do is find out what code is making the light come on it will have a # P0 - - - the MAF or mass air flow sensor on this vehicle would be P0102 or P0103 its the first sensor and a main sensor that would create a lot of driveably problems but the code would be there . How the dealer got from the maf to replaceing the transmission and ovesely that was not the problem and now it telling you you need a new alternator is eighter criminal or complete incompants. Find out what the code is and i will tell you what is wrong with it and don't go back to that dealer you didn't need any of these parts . Any auto parts store will read these codes at no charge for you this is why the OBD 11 system is there and is standard on all vehicles with a few exceptions in the us but not your vehicle and regulated by the federial goverment . I work on vehicles and owen one a blazer my self witch is the same thing as a jimmy. And you are getting riped off pier_j

Posted on Mar 17, 2011

gyver

  • 120 Answers

SOURCE: 95 GMC K1500 350... replaced distributor...timed

ok ran great before changes. right. you say unpluged computor to set timing.. yes.. do you mean the plug on the firewall passenger side that looks like a fuse holder kindof..?? (set timing connector ) (tan /blk wire)
did it run good during timing proceedure??? wont be MAP that is engine vacume has nothing to do with what you have replaced.
proceedure is to set timing . shut off engine , plug in.. then restart.
yes timing moves as per ECM specs. check that timing did no get out one tooth when you replaced distributor. retime . restart

Posted on Feb 01, 2012

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