Ok, I need some help. I have a 2008 with the 4-Liter boat anchor and I'm having some trouble.

After extended driving at speed (65-85 MPH on the highway) the engine dies when it comes back down to an idle. This only happens when the motor is up to temp and it just started today after I filled up at a Chevron station. I filled it up with premium (with Techron) which I do regularly but not at Chevron. This is the first issue I've had with the car in over two years of having it. It's not driven rough and 80% of it's 29,500 miles are highway miles.

Could it be the ECU adjusting to this premium gas? Could it be bad gas? Not sure what to do here. Feedback?

 

Thanks for moving this Boomer.

 

My first hunch would be fuel system related. Maybe the techron is loosening up some junk and an injector is restricted. Works fine at full speed but the restriction doesn't let enough flow at idle.

Maybe take her out and after good and warm put it thru its paces up to redline a number of times. The Italian tune up thing.

I'm not that experienced with injector issues, but when my old F150 (carb) starts acting up - rough idle/low idle and sometimes some bucking when I goose it, I buy a bottle of gumout regane (probably like techron) with a fresh tank of gas, run it thru its paces up to redline and pull a couple of long hills. After about a 1/4 tank is used it starts running great. Its also supposed to clean out carbon build up on the plugs, valves, combustion chamber. Cheap tune-up.

You might actually need a bottle of techron - the minute amount in Chevron fuel may not be enough to purge and stuff in the fuel system.

Just a hunch....