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  1. M

    2003 Tahoe 5.3 VIN-Z - P0300 With a Twist

    Hi Everyone Thought I would provide an update. Pulled the valve covers and lifters were fine. Ran a compression check and all were even except #5. #5 was higher and the more I cranked the higher it got. We all know that’s not how it is supposed to work. Pulled the engine this weekend...
  2. M

    2003 Tahoe 5.3 VIN-Z - P0300 With a Twist

    I agree and I thought that in the beginning but after driving it 10-15 miles … I would think the O2 sensors would have been hot enough
  3. M

    2003 Tahoe 5.3 VIN-Z - P0300 With a Twist

    Well, your post made up my mind. I’m going to pull the valve covers this week to see. I’m pretty competent at troubleshooting and can’t remember a time something had me this stumped. Time to go back to the basics and see if the mechanical parts are working.
  4. M

    2003 Tahoe 5.3 VIN-Z - P0300 With a Twist

    Dang, I feel like we are in the same boat. I thought lifters but thought I ruled it out because for a while it was intermittent. The problem seems more steady at this point although the severity of the miss goes from bad to worse. I just finished doing the 'node test' but using a test light...
  5. M

    2003 Tahoe 5.3 VIN-Z - P0300 With a Twist

    Well, in the truest sense, yes, I keep a copy of the base tunes and flash it back. That said, unlike my other vehicles the only thing ‘tuned’ on this one is the pulse calibration for the taller tires. Tune hasn’t been touched in 2+ years. That was why I was thinking the PCM was defective...
  6. M

    2003 Tahoe 5.3 VIN-Z - P0300 With a Twist

    I agree and that is what finally caught my attention. I have removed the PCM, cleaned the pins with contact cleaner, and reinstalled. No signs of corrosion. Another thing to add is all four O2 sensors replaced with factory O2 sensors. Also, the problem seems to be tied to cylinder #3...
  7. M

    2003 Tahoe 5.3 VIN-Z - P0300 With a Twist

    Folks, the dreaded P0300 but quite the twist. Solve this one, tell me drink of choice, and I will figure out how to get it to you! Background: 2003 Chevy Tahoe Z71 5.3 Flex with 300K on the clock. Intake manifold gaskets replaced (twice for good measure - squeaky clean surfaces) New GM MAP New...
  8. M

    AC - Extreme High Pressure on “High Side”

    Yes, this is an 03 with the clutch fan. While it may or may not be working perfectly - it is moving considerable air.
  9. M

    AC - Extreme High Pressure on “High Side”

    Thanks for the reply. I tried all three situations. Front only, rear only and both. The only change with both running was an increase in time to build the higher pressure. I took it to a friends shop and had them pull out two oz on refrigerant. Suddenly… it is back to working normally...
  10. M

    AC - Extreme High Pressure on “High Side”

    Thank you. Here she is. Sorry it isn’t the full truck but simply a picture I could find on my phone.
  11. M

    AC - Extreme High Pressure on “High Side”

    Hi Folks So I have a strange one and I suspect I know what I will find but wanted opinions first. 2003 Tahoe Z71 Automatic Climate Control with Aux Cooling in rear. 5.3L with about 300K on the clock. I have owned it the last 70K. As background I was a GM tech 20 years ago so I know I’m...

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