Surge at steady cruise & little lope at idle (SOLVED)

[exp500]

Did you check Evap lines for leaks?

 

[exp500]

How fast do injectors leak down? How long will it hold pressure key off?

 

[swathdiver]

I'm looking for some new ideas for trouble shooting a 2003 Tahoe I recently inherited. It is a 5.3 Flex Fuel with 207k miles.
It has a soft miss at idle and has a mild surge when at a steady cruise speed. Acceleration is good and starts up instantly.

What brand and octane of fuel are you burning and what is your alcohol content?

Another way to test the fuel system pressure is to get a gauge with a long hose and stick it on the windshield and then go WOT on an on-ramp up to highway speed. The pressure should not drop more than a pound or so. I do not know if your fuel pressures can be seen with a Tech-2 or scan tool or OBDII adapter and phone app.

Did you check the gap on all of the plugs? They come already gapped and I have sometimes found them off a little and adjusted them to the correct gap, carefully.

 

[Kc5khr]

FIXED I think.
Replaced the Chinese 'Spectra Premium' throttle body with the GM one and it appeared to fix the surge. If whoever put the Spectra on there had spent another $10, they could have bought the GM.
I have driven about 35-40 miles and all is good....for now.
Long term fuel trims are back to normal as well.
I'm guessing it wasn't giving the computer an accurate throttle position feedback.

 

[swathdiver]

FIXED I think.
Replaced the Chinese 'Spectra Premium' throttle body with the GM one and it appeared to fix the surge. If whoever put the Spectra on there had spent another $10, they could have bought the GM.
I have driven about 35-40 miles and all is good....for now.
Long term fuel trims are back to normal as well.
I'm guessing it wasn't giving the computer an accurate throttle position feedback.

Awesome, I was thinking of that as well, these trucks don't take kindly to aftermarket parts, especially from commies!

 

[Kc5khr]

Appreciate all of the advice and tips from everyone.

 

[exp500]

Please EDIT post title, add "SOLVED". Thanks