2001 Yukon Denali Low Speed Surging and P0404

Discussion in 'Chevy Suburban Forum (GMC Yukon XL)' started by sjajf16, Aug 29, 2013.

  1. sjajf16

    sjajf16 New Member

    Hello all, new to the forum and hoping someone here can help.

    I have a 2001 Denali XL that has been driving me nuts for a week now. Here is the skinny and what I have done:

    Started getting a low speed surge in engine, it happens around 15-25 MPH with RPM of around 1000. Light pressure on pedal trying to maintain speed and engine starts fluxuating and surging between 500 and 1000 RPM. As soon as I start to accelerate, surging smooths out and stops and engine runs great with no fall off in mileage, Set cruise at 50 MPH at around 1800 RPM and engine is solid.

    Also been popping a P0404 and occasionaly a P0405 with it after extended running. Replaced EGR and problem came back. Checked all voltages and signals at EGR harness including 12 VDC power, 5 VDC reference, pintle position signal (with valve unbolted and moving pintle), and grounds. All looked good.

    I have also removed and cleaned the throttle body and replaced the throttle position sensor. When I took off the TPS, it has a movable piece that slips over butterfly shaft which seemed to have a lot of loose play in it. The new sensors piece was more solid and seemed to have a "tension" feel to it. I thought I was on to something as maybe the computer had problems setting throttle position with a bad sensor.

    Well as of today, vehicle is still doing the exact same thing. Low engine surge and had the service engine soon light on by the time the wife got to work.

    Any help or suggestions appreciated
  2. unsub

    unsub New Member

    I had the 404 code on my 2001 Suburban LT 4x4 5.3 Vortec along with another code I forget, but I have a awesome mechanic and all he did was replace a O2 sensor and ran Seafoam through the brake booster or one of the vacuum lines to clean everything out inside the engine. No more codes. Runs great. I also had the same symptoms you did along with slight erratic idles when not moving in P, N and D. He thinks it was the O2 replacement that fixed it as he does not believe in cheap fixes like my request for him to run Seafoam through my engine.

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