2006 Hummer H3 very poor mileage all of the sudden
2006 hummer h3, 5 cyl. About 125k miles.
Used to get at least 15 mpg, now it's more like 10 mpg.
I changed the spark plugs, air filter, ignition coil.
Ran some injector cleaner.
Still no luck.
No engine light on/no code. My scanner is an actron cp9580 but beside reading and after repair removing code that's all I know to do with it.
Start with checking the fuel trim data.
Couldn't figure out how to add pics...here is a slideshow of what the scanner shows
I put 10 seconds between each slide so it can be read..