MY YUKON SEEMS TO HESITATE SLIGHTLY WHEN YOUR LEAVING A STOPLIGHT AN BEGIN TO PRESS ACELORATOR

If you are getting a check engine or dash light check for codes
Really I think it could be fuel, air or back pressure. It is a good thing to have codes sometimes.
Below a few thing which my help

http://www.autotap.com/problem4_engine_hesitates.asp
https://www.youtube.com/watch?v=bDCaAZedVYY

https://www.yourmechanic.com/estimates/gmc/yukon-xl-1500/engine-hesitates-during-acceleration-inspection
https://www.youtube.com/watch?v=cXHfJTbcSgY


https://www.youtube.com/watch?v=-SRgNXKoOC8
https://www.gm-trucks.com/forums/topic/200207-yukon-xl-denail-2009-severe-hesitation-and-poor-gas-milage-real-head/

REPLACE YOU FUEL PRESSURE REGULATOR THATS YOU PROBLEM OK WANT TO DIAGNOSE PROBLEM LET ME KNOW ILL HELP IM A MECHANIC

Hello
I would rebuild the carburetor or check the intake for vacuum leaks or leaking vacuum hoses, all these cause a lean mixture of fuel and that causes hesitation. The EGR valve opening to early due to a defective delay or other control device can also cause hesitation, disconnect the EGR to confirm the problem lies there and repair if needed

• Push the driver's seat as far back as possible, allowing you to lay on the floor on the driver's side.
  
• 2 Shine a flashlight at the top of the brake pedal stalk and find the stoplight switch. It will be a plastic cube either connected to the brake stalk or directly opposite the brake stalk, depending on the vehicle.
  
• 3 Depress the brake pedal and feel where the brake light switch contacts the stopping plate, a metal plate in direct line with the stoplight switch.
  
• 4 Feel for an open hole where the stoplight's plunger-style button presses. If a hole is present, you simply need to replace the rubber stopper.
  
• 5 Press and release the plunger-style button on the brake light switch and ask an assistant if the brake lights are turning off and on. If not, the switch is bad and must be replaced.
  

Stoplight Switch Stopper Replacement

• 1 Clean out any remaining debris left behind by the old stopper from the hole that the stopper goes into.
  
• 2 Press the new stopper into the hole on the metal plate until it snaps into place.
  
• 3 Shine the flashlight on the stopper and check that it sits flush against the metal plate.
  
• 4 Press and release the brake pedal and ask your assistant if the brake lights are turning off and on.
  
• 5 Replace the stoplight switch if the lights continue to stay on.
  

Stoplight Switch Replacement

• 1 Loosen and remove the bolts holding the stoplight switch in place. It could be between one and four bolts depending on the vehicle.
  
• 2 Pull the stoplight switch from its mount. Disconnect the wiring harness from the stoplight switch by pressing or pulling the locking tab and puling the harness away from the switch.
  
• 3 Plug the wiring harness into the new switch until the locking tab clicks into place.
  
• 4 Place the new switch on the mount the old switch was removed from and tighten the bolts with a ratchet and socket.
  
• 5 Press and release the brake pedal several times and have your assistant check for proper operation.
  

This is a very common problem and GM has issued about 4 service bulletins depending on which trouble codes are stored. Get your codes read and post them here.

scan the computer with a computer scanner just to see what it says. check your intake, I am thinking your mass air flow sensor is no good. it happened to my car where the rpm increases and decreases when the car is idle. Or it can be the IAC valve.

Have the spark plugs and spark plug wires ever been replaced? Sounds like an ignition misfire.

Chk MAF sensor (mass air flow) first sensor in ducting coming out of air filter.

* Use only one foot on the gas peddle - Just teasing. :)

you may also want to consider that the coil pack is failing... i remember when my windstar coilpack failed i had an awful time just getting up a small hill... can't recall if it shuddered tho.

Robert

run the fault codes
check for problem ambient temp sensor, baro sensor , maf/vaf sensor problems