Having an issue with the Silverado. The truck started running a little rough when I drove it last and is now running in open loop idling at 12-12.5 AFR. While the truck is in open loop it seems to run fine, but will stall occasionally. Using HP tuners if I command closed loop Long term fuel trim on bank 2 goes to 25% and Short term is in the high mid 30's within a few seconds. I've checked fuel pressure and it is right at 59psi. I've swapped o2 sensors side to side to see if the lean condition followed the sensor, no luck. I've sprayed the intake down with brake cleaner along the cylinders head and haven't found any obvious leaks. Also did a cylinder balance test with HP tuners and all cylinders are 97-98%. Out of ideas at the moment. Any suggestions would be helpful.

 

Log file. CL commanded at 1:06.

 

If the intake gasket looks like this, it's probably no good. This is a sample of a bad gasket. Notice the flattened rubber lip.

I can't remember if I had 1 side lean or both sides. No noticeable change when sprayed from top side. When I pulled of the intake you could see where it was sucking air on the bottom side. I never took pictures of mine but I came across these and thought I would share So you know what your looking at.





Gasket smashed flat.

 

B2 S1 O2 stuck at 550-560mv. Even with bad manifold gaskets you would get more increase in O2 mv with trims adding 75% fuel and the IPW doubling from the drivers side. Sure looks like a bad O2. You sure you swapped the pre cat sensors side to side?

 

So in OL its rich then when you enable trims its even more rich (adding 50% fuel)?

What is the idle rpm doing? Intake leaks will generally make it idle higher.

Swap the injectors side to side.

 

I was thinking the same thing if the gasket was leaking it would have been getting higher readings on the sensor. I did swap the sensors. I'm going to check wiring tonight and make sure I don't have any other issues. Picking up a set of gaskets on the way home and will swap them if everything else checks out.

 

When I command closed loop my wideband shows around 14.7 (in bank 1) bank 2 will go to 25% LTFT and 50% STFT. Idle is 750rpm. It will drop slightly in CL.

 

When you search hard enough you will find the problem. Broken wire in the passenger side O2 harness.