Idle surge and rough idle

[green.joel2]

Hello all,

 

This is my first post on this forum.  Last year I bought a 2009 Chevy Silverado 1500 Ext cab LT with a 5.3l V8 that is Flexfuel capable.  Well, I never intended to use flex fuel, but last week, I did so on the spur of the moment.  We drove about 3/4 of the tank gone.  Then as I was pulling up to the gas station to refill before going out of town for work, my truck's idle began dropping and feeling like it is about to stall out at idle.  This happens whether park is engaged or not.  I filled up, put some seafoam in my tank and drove about 1.5 hours to work.  It continued to idle like this all throughout the trip and even later when I went out and sat at idle while on my break.  What could be the problem? I can't imagine that an engine that is meant for flex fuel could get that messed up by it.  A side note: we had the transmission rebuilt in January, just in case that makes a different.  It has only been a few weeks since last oil change.  All fluids were checked and filled up at that time and have been checked a couple of times since.

[riverbanks]

Sometimes a coincidence, sometimes not,have you cleaned the MAF?how about taking a look at throttle body,dirty?read up on cleaning that, wrong way will make idle(hunting),and might need a relearn

[diyer2]

When was the last tune up?

MAF cleaner is available.

 

[Huggy16]

Mine was kinda doing the same thing! If you check out my post it might help you, definitely recommend a tune up

[sefiroxx]

Confirm tuneup, then

- clean throttle body and butterfly, could be sticking
- check tps readings, especially when manually moving butterfly to ensure smooth change in readings
- confirm O2 and ft readings are reasonable
- drive by wire, throttle motor could be going