3PedalMINI Posted February 26, 2012 Share Posted February 26, 2012 my mom has a 2002 GMC Yukon XL 5.3l vortec 1500 with 90k on the clock. When slowing down and at idle the engine shakes violently. This scared the poo out of my mom and brought it home. Thinking it was just a quirk i took it out around the block and i confirmed the violent shaking. I promptly took it down to autozone and had the code read. the oxygen sensor is thrown and so is a random misfire. He said that rarely do those go together so it is more then likely the misfire thats throwing the oxygen sensor. Any tech bulletins out that has this issue? i want to be somewhat informed when I take it in for her as we have never had luck with mechanics. TIA we really appreciate it. I am somewhat car competent and can check somethings if you need me to. Link to comment Share on other sites More sharing options...
Big O Posted February 26, 2012 Share Posted February 26, 2012 Check and make sure all plug wires are in good shape (not burnt or eaten on) and plugged in well. Did it come on all of a sudden or has it been happening and just getting worse? Link to comment Share on other sites More sharing options...
dipolley Posted February 26, 2012 Share Posted February 26, 2012 It is hard to say anything for sure without seeing the car. I would start by changing the spark plugs and checking all the wires and connections. If one cylinder is misfireing, then the excess gas that isn't being burned off will trip the O2 sensor. At higher RPMs you may not notice the misfire as the other cylinders are making up for it. But at low RPMs you will definitly notice. I would also have an induction flush performed before you change the plugs. You can have this done at most oil change shops. It is a chemical cleaning of the engine that sprays a liquid (ussually sea foam) into the brake booster vacuum line or after the MAF in the air intake. It breaks up all the carbon depsits and blows it out the exhaust. It can foul out the plugs though. Link to comment Share on other sites More sharing options...
DAVE SXT Posted February 26, 2012 Share Posted February 26, 2012 Not a GM Tech, but at 90K I'm almost certain the plugs and more than likely the wires need replaced. They are typically good for about 90-100K. I also agree with the "flush" and I would also have them "manually" clean the throttle body as well. A fuel filter replacement would also not hurt, unless it has been replaced within 24K. And, don't forget to check the air filter. Link to comment Share on other sites More sharing options...
02Xtreme07ss Posted February 26, 2012 Share Posted February 26, 2012 Just to add to what has already been suggested here, GM's MAF system is tied into every other engine/emission management system in the vehicle. If the MAF is even the slightest bit dirty, you will get all sort of odd codes and driveability issues. A $5 can of CRC MAF Sensor cleaner and 10 minutes of your time and you can rule out an incorrect reading being the problem. Link to comment Share on other sites More sharing options...
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