2004 Tahoe Engine Surge and Stuck in 3rd Gear - 5.3 4L60E

[Tynan918]

Went with my older brother to look at a 2004 Tahoe with a rebuilt 5.3 with only 5,000 miles on it.

I took it for a test drive around the town we were in, doing about 40mph at most, floored it once or twice for a second, everything seemed fine.

We bought it and I drove on the interstate to get it back home, speed limit is 85 mph.

Since we we're already going 85 mph, I wanted to open it up and see what all it could do and put my foot all the way to the floor.

3 problems:

1. Low Oil Pressure - oil pressure stays at 20 or below PSI. All other gauges seem fine.

2. Performance Surging - After about 10 minutes of interstate driving, the engine seemed to either shut down or lose fuel and would cut back on after a couple of seconds. The stopping force during this felt as if I was barely applying the brake. I feel this force everytime I take my foot of the brake pedal.

3. Transmission No 4th Gear - Transmission shifts through 1-3 just fine and about 80-100 mph in 3rd gear, but I floor it and when it attempts to shift into 4th gear, the speedometer stays stuck at 100 mph and the RPM'S shoot to 4,000 and stays stuck until I let off of the gas pedal. Here's some footage I caught of this problem:

Once we got home, I put my OBD2 scanner to see the DTC's, and there is 6 :

1. P0171 - System Too Lean in Bank 1
2. P0174 - System Too Lean in Bank 2
3. P0300 - Random/Multiple Cylinder Misifire Detected
4. P0327 - Knock/Combustion Vibration Sensor A Low Circuit
5. P0300 - Random/Multiple Cylinder Misifire Detected
6. P0327 - Knock/Combustion Vibration Sensor A Low Circuit

What's going on and where do I start fixing the issue ? Replace the 02 sensors, tune up with wires, plugs, and coil packs, and inspect the wiring on knock sensor A ?

Would that also fix the shift and lack of power issues or those are unrelated to the DTC's ?

 

[strutaeng]

Oh man. Several issues going on there.

At least the lean codes is one issue. The misfire another issue(?) The knock codes may be just be false codes from the misfires and may away if that's resolved.

Step one to address the lean codes: go buy a fuel pressure gauge. Check with key on, engine off. What is the pressure? Does it hold the pressure for about 15 minutes? Fire it up and report the fuel pressure. Flip the throttle and what does the pressure do? I would first address the lean codes before anything else...

Welcome to the forum BTW!

 

[rockola1971]

First problem here is if you want a race car, go get one. A Tahoe aint it. Id almost bet 2nd gear isnt there too. Put it in 4th and romp on the trottle and see if they RPM's jump like a frog and the tranny tranny starts slipping into another year. That would be the 2-4 band burnt up which is needed from 1-2 and 3-4 shifts. Not sure about the 2004 but 1999 Sierra shutdown at 99mph and acted like it was starved of fuel and if you backed off the throttle just a little bit it would come out of it. The reason was is that there were no further instructions in the PCM on what to do for 100mph+. Basically a governor put in by GM.