afternoon commute shut off - 2003 Tahoe 5.3 flex

Discussion in 'GM Powertrain' started by fivestrong, Jul 16, 2010.

  1. fivestrong

    fivestrong New Member

    2003 Tahoe 5.3 flex has had an intermittent issue for about 1 1/2 years now. It only does it on really warm afternoons. I have a 30 mile commute home. Generally, I'll make it 1/2 way home before it just cuts out. I pull off with engine sputtering, but no throttle response. It will finally die and not restart for a couple minutes. No check engine lights. The engine will restart as nothing ever happened. Sometimes I make it the rest of the way, others, I have to repeat the process. It ONLY does this on hot days and in the afternoon...It runs like a top the rest of the time. It ran all winter without an episode as well. In 1 1/2 it has had a fuel pump, filter, crank sensor, and fuel pump relay. All initially appeared to fix it, but to no avail. Finally, it got so bad and frequent, that I had to be towed. HELP!!!!!
  2. jlwz71

    jlwz71 New Member

    Without a scanner hooked up and watching the data stream, if you want a guess check the cam sensor. Its on the top of the engine in the back behind the manifold. Kinda hard to get to. A vehicle will run with a bad cam sensor. It is primarily used to sync injectors to intake valve opening, which if affected by heat breaking it down it will sputter and the engine will eventually stall until latent heat is dissipated. Also I have seen the key switch go bad. Just a couple of guesses.
  3. MrShorty

    MrShorty Epic Member 5+ Years 1000 Posts

    Even if the CEL is not coming on, I'd probably put a scanner on it and pull codes. There might be something in pending codes that would point to a solution. I would probably also put a fuel pressure gauge on it and see what fuel delivery is doing when it loses power. Your symptoms remind me of my Explorer that sometimes dies when it gets hot from an overheating fuel pump.
  4. fivestrong

    fivestrong New Member

    Tried a couple obvious things over the weekend. 1st.- replaced the fuel filter. 2nd.- got fuel pump operating specs. 3rd.- hooked up fuel pressure gauge and checked with just ignition on, and then running. GM states that 47-53 psi normal with key on. Mine's within specs. Drops to 42psi running. Left gauge hooked up for quick diagnosis if & when symptoms return.
    Removed and cleaned throttle assembly to alleviate low, rough idle. Removed and cleaned Mass Air sensor while air induction hose was off. Also, using just my ignition key in switch, just in case my big wad of keys was affecting the switch. Drove it on 4 separate occasions over the weekend in 95 + degree heat, only for short 10-15 mile trips. Running like a top. I know however, that the 1st time I venture to work, will be the test. I don't have an OBDII for scanning purposes, but when I experienced the 1st occurrence it was, and there were no codes. Still no Check engine Lights, except for the last occurrence.....when it started dying, I threw the transmission in neutral and matted the accelerator. The engine started popping back through the intake, the check engine light came on, and then she died. 2 minutes later it re cranked like nothing happened. I'm going to drive it until it dies again with the gauge on it and check fuel pressure. The problem is, if its the ignition switch, it won't allow the fuel pump to come on either. Any thoughts?
  5. hundojoe

    hundojoe Rockstar 100 Posts

    Try checking the connections at the battery, see if there is any corrosion on the male/female threads, also check battery cables at the starter. Then check the main wiring harness at the computer, then lastly check every ground cable you can find.

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