So i have a 2008 205k and i noticed on highway at steady speed i get an occaisional fart like minor hesitation similar in feeling of going over asphalt ripple joint. Could be intake backfire? Or exhaust backfire? Its minor. Even like 1 cyl cuts out for split second? No check engine light when it happens but i do have a code for bank 1 too lean. Comes and goes. I changed front 3 plugs which number 5 was electrode worn down to ceramic. Change did not improve issue. Back 6 months ago i was getting a map sensor code but that went away with daily driving vehicle had been sitting for months. I am not familiar with any vac leak problems on 3.9s . want to change back plugs but does not look easy......i bought this march 2021 but let it sit til april 2022. Guy i bought it from it had been sitting awhile too.

 

Welcome from Florida. With all that sitting it needs a good cleaning and tune up. Probably needs fresh gas also.

 

Was looking under hood and some under vehicle and it has alot of sitting rust look. The rear quarter in front of tires is rusty both side passenger is worse bigger holes. Under hood i noticed it looks like an electronic throttle assembly. Dont like that. The sitting may have caused some electrical issues sensors etc. Damp days i get abd traction lights on. 1 of the tire pressure sensors quits randomly. Today another 1 gave wrong reading said low 26 but tire was fine. Starting to hear a wheelbearing i think. Im getting feeling the miss only happens in overdrive above 50mph more observation needed.

 

It's an old car with many miles on it that probably was not well maintained.

 

Im getting a bank 1 lean code after driving awhile. After misfire type event happens. I'm also getting a every 200 feet in overdrive kinda shudder like I'm running over ripples in road. Like road edge warning strips by only more subtle. The misfire type event happens after 15 or 20 miles of mixed driving. It may only be noticeable in overdrive not sure